[PATCH 0/2] link vdso with linker

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18 messages, 6 authors, 2022-03-02 · open the first message on its own page

[PATCH 0/2] link vdso with linker

From: Nick Desaulniers <ndesaulniers@google.com>
Date: 2020-09-01 22:25:40 

Kees Cook is working on series that adds --orphan-section=warn to arm,
arm64, and x86.  I noticed that ppc vdso were still using cc-ldoption
for these which I removed.  It seems this results in that flag being
silently dropped.

I'm very confident with the first patch, but the second needs closer
review around the error mentioned below the fold related to the .got
section.

Nick Desaulniers (2):
  powerpc/vdso64: link vdso64 with linker
  powerpc/vdso32: link vdso64 with linker

 arch/powerpc/include/asm/vdso.h         | 17 ++---------------
 arch/powerpc/kernel/vdso32/Makefile     |  7 +++++--
 arch/powerpc/kernel/vdso32/vdso32.lds.S |  3 ++-
 arch/powerpc/kernel/vdso64/Makefile     |  8 ++++++--
 arch/powerpc/kernel/vdso64/vdso64.lds.S |  1 -
 5 files changed, 15 insertions(+), 21 deletions(-)

-- 
2.28.0.402.g5ffc5be6b7-goog

[PATCH 1/2] powerpc/vdso64: link vdso64 with linker

From: Nick Desaulniers <ndesaulniers@google.com>
Date: 2020-09-01 22:25:42 

Rather than invoke the compiler as the driver, use the linker. That way
we can check --orphan-handling=warn support correctly, as cc-ldoption
was removed in
commit 055efab3120b ("kbuild: drop support for cc-ldoption").

Painstakingly compared the output between `objdump -a` before and after
this change. Now function symbols have the correct type of FUNC rather
than NONE, and the entry is slightly different (which doesn't matter for
the vdso). Binary size is the same.

Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 arch/powerpc/include/asm/vdso.h         | 17 ++---------------
 arch/powerpc/kernel/vdso64/Makefile     |  8 ++++++--
 arch/powerpc/kernel/vdso64/vdso64.lds.S |  1 -
 3 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/include/asm/vdso.h b/arch/powerpc/include/asm/vdso.h
index 2ff884853f97..11b2ecf49f79 100644
--- a/arch/powerpc/include/asm/vdso.h
+++ b/arch/powerpc/include/asm/vdso.h
@@ -24,19 +24,7 @@ int vdso_getcpu_init(void);
 
 #else /* __ASSEMBLY__ */
 
-#ifdef __VDSO64__
-#define V_FUNCTION_BEGIN(name)		\
-	.globl name;			\
-	name:				\
-
-#define V_FUNCTION_END(name)		\
-	.size name,.-name;
-
-#define V_LOCAL_FUNC(name) (name)
-#endif /* __VDSO64__ */
-
-#ifdef __VDSO32__
-
+#if defined(__VDSO32__) || defined (__VDSO64__)
 #define V_FUNCTION_BEGIN(name)		\
 	.globl name;			\
 	.type name,@function; 		\
@@ -46,8 +34,7 @@ int vdso_getcpu_init(void);
 	.size name,.-name;
 
 #define V_LOCAL_FUNC(name) (name)
-
-#endif /* __VDSO32__ */
+#endif /* __VDSO{32|64}__ */
 
 #endif /* __ASSEMBLY__ */
 
diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile
index 38c317f25141..7ea3ce537d0a 100644
--- a/arch/powerpc/kernel/vdso64/Makefile
+++ b/arch/powerpc/kernel/vdso64/Makefile
@@ -32,9 +32,13 @@ $(obj)/%.so: OBJCOPYFLAGS := -S
 $(obj)/%.so: $(obj)/%.so.dbg FORCE
 	$(call if_changed,objcopy)
 
+ldflags-y := -shared -soname linux-vdso64.so.1 \
+	$(call ld-option, --eh-frame-hdr) \
+	$(call ld-option, --orphan-handling=warn) -T
+
 # actual build commands
-quiet_cmd_vdso64ld = VDSO64L $@
-      cmd_vdso64ld = $(CC) $(c_flags) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) $(call cc-ldoption, -Wl$(comma)--orphan-handling=warn)
+quiet_cmd_vdso64ld = LD      $@
+      cmd_vdso64ld = $(cmd_ld)
 
 # install commands for the unstripped file
 quiet_cmd_vdso_install = INSTALL $@
diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S
index 4e3a8d4ee614..58c33b704b6a 100644
--- a/arch/powerpc/kernel/vdso64/vdso64.lds.S
+++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S
@@ -11,7 +11,6 @@ OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle")
 OUTPUT_FORMAT("elf64-powerpc", "elf64-powerpc", "elf64-powerpc")
 #endif
 OUTPUT_ARCH(powerpc:common64)
-ENTRY(_start)
 
 SECTIONS
 {
-- 
2.28.0.402.g5ffc5be6b7-goog

[PATCH 2/2] powerpc/vdso32: link vdso64 with linker

From: Nick Desaulniers <ndesaulniers@google.com>
Date: 2020-09-01 22:25:45 

Rather than invoke the compiler as the driver, use the linker. That way
we can check --orphan-handling=warn support correctly, as cc-ldoption
was removed in
commit 055efab3120b ("kbuild: drop support for cc-ldoption").

Requires dropping the .got section.  I couldn't find how it was used in
the vdso32.

Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Not sure removing .got is a good idea or not.  Otherwise I observe the
following link error:
powerpc-linux-gnu-ld: warning: orphan section `.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.got'
powerpc-linux-gnu-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc-linux-gnu-ld: final link failed: bad value

sigtramp.c doesn't mention anything from the GOT AFAICT, and doesn't
look like it contains relocations that do, so I'm not sure where
references to _GLOBAL_OFFSET_TABLE_ are coming from.

 arch/powerpc/kernel/vdso32/Makefile     | 7 +++++--
 arch/powerpc/kernel/vdso32/vdso32.lds.S | 3 ++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile
index 87ab1152d5ce..611a5951945a 100644
--- a/arch/powerpc/kernel/vdso32/Makefile
+++ b/arch/powerpc/kernel/vdso32/Makefile
@@ -27,6 +27,9 @@ UBSAN_SANITIZE := n
 ccflags-y := -shared -fno-common -fno-builtin -nostdlib \
 	-Wl,-soname=linux-vdso32.so.1 -Wl,--hash-style=both
 asflags-y := -D__VDSO32__ -s
+ldflags-y := -shared -soname linux-vdso32.so.1 \
+	$(call ld-option, --eh-frame-hdr) \
+	$(call ld-option, --orphan-handling=warn) -T
 
 obj-y += vdso32_wrapper.o
 extra-y += vdso32.lds
@@ -49,8 +52,8 @@ $(obj-vdso32): %.o: %.S FORCE
 	$(call if_changed_dep,vdso32as)
 
 # actual build commands
-quiet_cmd_vdso32ld = VDSO32L $@
-      cmd_vdso32ld = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ $(call cc-ldoption, -Wl$(comma)--orphan-handling=warn) -Wl,-T$(filter %.lds,$^) $(filter %.o,$^)
+quiet_cmd_vdso32ld = LD      $@
+      cmd_vdso32ld = $(cmd_ld)
 quiet_cmd_vdso32as = VDSO32A $@
       cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) -c -o $@ $<
 
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 4c985467a668..0ccdebad18b8 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -61,7 +61,6 @@ SECTIONS
 	.fixup		: { *(.fixup) }
 
 	.dynamic	: { *(.dynamic) }		:text	:dynamic
-	.got		: { *(.got) }			:text
 	.plt		: { *(.plt) }
 
 	_end = .;
@@ -108,7 +107,9 @@ SECTIONS
 	.debug_varnames  0 : { *(.debug_varnames) }
 
 	/DISCARD/	: {
+		*(.got)
 		*(.note.GNU-stack)
+		*(.branch_lt)
 		*(.data .data.* .gnu.linkonce.d.* .sdata*)
 		*(.bss .sbss .dynbss .dynsbss)
 		*(.glink .iplt .plt .rela*)
-- 
2.28.0.402.g5ffc5be6b7-goog

Re: [PATCH 2/2] powerpc/vdso32: link vdso64 with linker

From: Kees Cook <hidden>
Date: 2020-09-02 02:59:02 

I think $subject needs a typo update... vdso32...

On Tue, Sep 01, 2020 at 03:25:23PM -0700, Nick Desaulniers wrote:
Rather than invoke the compiler as the driver, use the linker. That way
we can check --orphan-handling=warn support correctly, as cc-ldoption
was removed in
commit 055efab3120b ("kbuild: drop support for cc-ldoption").

Requires dropping the .got section.  I couldn't find how it was used in
the vdso32.

Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Not sure removing .got is a good idea or not.  Otherwise I observe the
following link error:
powerpc-linux-gnu-ld: warning: orphan section `.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.got'
powerpc-linux-gnu-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc-linux-gnu-ld: final link failed: bad value
If it's like the x86 and arm toolchains, I think you'll be required to
keep .got, but you can assert it to a 0 size, e.g.:

	/*
	 * Sections that should stay zero sized, which is safer to
	 * explicitly check instead of blindly discarding.
	 */
	.got : {
		*(.got)
	}
	ASSERT(SIZEOF(.got) == 0, "Unexpected GOT entries detected!")

(and put that at the end of the linker script)


-Kees
quoted hunk
sigtramp.c doesn't mention anything from the GOT AFAICT, and doesn't
look like it contains relocations that do, so I'm not sure where
references to _GLOBAL_OFFSET_TABLE_ are coming from.

 arch/powerpc/kernel/vdso32/Makefile     | 7 +++++--
 arch/powerpc/kernel/vdso32/vdso32.lds.S | 3 ++-
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile
index 87ab1152d5ce..611a5951945a 100644
--- a/arch/powerpc/kernel/vdso32/Makefile
+++ b/arch/powerpc/kernel/vdso32/Makefile
@@ -27,6 +27,9 @@ UBSAN_SANITIZE := n
 ccflags-y := -shared -fno-common -fno-builtin -nostdlib \
 	-Wl,-soname=linux-vdso32.so.1 -Wl,--hash-style=both
 asflags-y := -D__VDSO32__ -s
+ldflags-y := -shared -soname linux-vdso32.so.1 \
+	$(call ld-option, --eh-frame-hdr) \
+	$(call ld-option, --orphan-handling=warn) -T
 
 obj-y += vdso32_wrapper.o
 extra-y += vdso32.lds
@@ -49,8 +52,8 @@ $(obj-vdso32): %.o: %.S FORCE
 	$(call if_changed_dep,vdso32as)
 
 # actual build commands
-quiet_cmd_vdso32ld = VDSO32L $@
-      cmd_vdso32ld = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ $(call cc-ldoption, -Wl$(comma)--orphan-handling=warn) -Wl,-T$(filter %.lds,$^) $(filter %.o,$^)
+quiet_cmd_vdso32ld = LD      $@
+      cmd_vdso32ld = $(cmd_ld)
 quiet_cmd_vdso32as = VDSO32A $@
       cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) -c -o $@ $<
 
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 4c985467a668..0ccdebad18b8 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -61,7 +61,6 @@ SECTIONS
 	.fixup		: { *(.fixup) }
 
 	.dynamic	: { *(.dynamic) }		:text	:dynamic
-	.got		: { *(.got) }			:text
 	.plt		: { *(.plt) }
 
 	_end = .;
@@ -108,7 +107,9 @@ SECTIONS
 	.debug_varnames  0 : { *(.debug_varnames) }
 
 	/DISCARD/	: {
+		*(.got)
 		*(.note.GNU-stack)
+		*(.branch_lt)
 		*(.data .data.* .gnu.linkonce.d.* .sdata*)
 		*(.bss .sbss .dynbss .dynsbss)
 		*(.glink .iplt .plt .rela*)
-- 
2.28.0.402.g5ffc5be6b7-goog
-- 
Kees Cook

Re: [PATCH 0/2] link vdso with linker

From: Nathan Chancellor <hidden>
Date: 2020-09-02 05:21:29 

On Tue, Sep 01, 2020 at 03:25:21PM -0700, Nick Desaulniers wrote:
Kees Cook is working on series that adds --orphan-section=warn to arm,
arm64, and x86.  I noticed that ppc vdso were still using cc-ldoption
for these which I removed.  It seems this results in that flag being
silently dropped.

I'm very confident with the first patch, but the second needs closer
review around the error mentioned below the fold related to the .got
section.

Nick Desaulniers (2):
  powerpc/vdso64: link vdso64 with linker
  powerpc/vdso32: link vdso64 with linker

 arch/powerpc/include/asm/vdso.h         | 17 ++---------------
 arch/powerpc/kernel/vdso32/Makefile     |  7 +++++--
 arch/powerpc/kernel/vdso32/vdso32.lds.S |  3 ++-
 arch/powerpc/kernel/vdso64/Makefile     |  8 ++++++--
 arch/powerpc/kernel/vdso64/vdso64.lds.S |  1 -
 5 files changed, 15 insertions(+), 21 deletions(-)

-- 
2.28.0.402.g5ffc5be6b7-goog
ppc44x_defconfig and powernv_defconfig start failing with this series
when LD=ld.lld is used.


$ make -skj"$(nproc)" ARCH=powerpc CROSS_COMPILE=powerpc-linux-gnu- LLVM=1 O=out/ppc32 distclean ppc44x_defconfig uImage
ld.lld: error: relocation R_PPC_REL16_LO cannot be used against symbol __kernel_datapage_offset; recompile with -fPIC
quoted
quoted
defined in arch/powerpc/kernel/vdso32/datapage.o
referenced by arch/powerpc/kernel/vdso32/gettimeofday.o:(__kernel_gettimeofday)
ld.lld: error: relocation R_PPC_REL16_LO cannot be used against symbol __kernel_datapage_offset; recompile with -fPIC
quoted
quoted
defined in arch/powerpc/kernel/vdso32/datapage.o
referenced by arch/powerpc/kernel/vdso32/gettimeofday.o:(__kernel_clock_gettime)
ld.lld: error: relocation R_PPC_REL16_LO cannot be used against symbol __kernel_datapage_offset; recompile with -fPIC
quoted
quoted
defined in arch/powerpc/kernel/vdso32/datapage.o
referenced by arch/powerpc/kernel/vdso32/gettimeofday.o:(__kernel_clock_getres)
ld.lld: error: relocation R_PPC_REL16_LO cannot be used against symbol __kernel_datapage_offset; recompile with -fPIC
quoted
quoted
defined in arch/powerpc/kernel/vdso32/datapage.o
referenced by arch/powerpc/kernel/vdso32/gettimeofday.o:(__kernel_time)
...


$ make -skj"$(nproc)" ARCH=powerpc CROSS_COMPILE=powerpc64le-linux-gnu- LLVM=1 O=out/ppc64le distclean powernv_defconfig zImage.epapr
ld.lld: error: relocation R_PPC64_REL16_LO cannot be used against symbol __kernel_datapage_offset; recompile with -fPIC
quoted
quoted
defined in arch/powerpc/kernel/vdso64/datapage.o
referenced by arch/powerpc/kernel/vdso64/gettimeofday.o:(__kernel_gettimeofday)
ld.lld: error: relocation R_PPC64_REL16_LO cannot be used against symbol __kernel_datapage_offset; recompile with -fPIC
quoted
quoted
defined in arch/powerpc/kernel/vdso64/datapage.o
referenced by arch/powerpc/kernel/vdso64/gettimeofday.o:(__kernel_clock_gettime)
ld.lld: error: relocation R_PPC64_REL16_LO cannot be used against symbol __kernel_datapage_offset; recompile with -fPIC
quoted
quoted
defined in arch/powerpc/kernel/vdso64/datapage.o
referenced by arch/powerpc/kernel/vdso64/gettimeofday.o:(__kernel_clock_getres)
ld.lld: error: relocation R_PPC64_REL16_LO cannot be used against symbol __kernel_datapage_offset; recompile with -fPIC
quoted
quoted
defined in arch/powerpc/kernel/vdso64/datapage.o
referenced by arch/powerpc/kernel/vdso64/gettimeofday.o:(__kernel_time)
ld.lld: error: relocation R_PPC64_REL16_LO cannot be used against symbol __kernel_datapage_offset; recompile with -fPIC
quoted
quoted
defined in arch/powerpc/kernel/vdso64/datapage.o
referenced by arch/powerpc/kernel/vdso64/cacheflush.o:(__kernel_sync_dicache)
...


We need Fangrui's patch to fix ppc44x_defconfig:

https://lore.kernel.org/lkml/20200205005054.k72fuikf6rwrgfe4@google.com/

That exact same fix is needed in arch/powerpc/kernel/vdso64/datapage.S
to fix powernv_defconfig.

Cheers,
Nathan

Re: [PATCH 2/2] powerpc/vdso32: link vdso64 with linker

From: Christophe Leroy <hidden>
Date: 2020-09-02 06:47:03 


On 09/01/2020 10:25 PM, Nick Desaulniers wrote:
Rather than invoke the compiler as the driver, use the linker. That way
we can check --orphan-handling=warn support correctly, as cc-ldoption
was removed in
commit 055efab3120b ("kbuild: drop support for cc-ldoption").

Requires dropping the .got section.  I couldn't find how it was used in
the vdso32.
ld crashes:

   LD      arch/powerpc/kernel/vdso32/vdso32.so.dbg
/bin/sh: line 1: 23780 Segmentation fault      (core dumped) 
ppc-linux-ld -EB -m elf32ppc -shared -soname linux-vdso32.so.1 
--eh-frame-hdr --orphan-handling=warn -T 
arch/powerpc/kernel/vdso32/vdso32.lds 
arch/powerpc/kernel/vdso32/sigtramp.o 
arch/powerpc/kernel/vdso32/gettimeofday.o 
arch/powerpc/kernel/vdso32/datapage.o 
arch/powerpc/kernel/vdso32/cacheflush.o 
arch/powerpc/kernel/vdso32/note.o arch/powerpc/kernel/vdso32/getcpu.o -o 
arch/powerpc/kernel/vdso32/vdso32.so.dbg
make[4]: *** [arch/powerpc/kernel/vdso32/vdso32.so.dbg] Error 139


[root@localhost linux-powerpc]# ppc-linux-ld --version
GNU ld (GNU Binutils) 2.26.20160125


Christophe
quoted hunk
Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Not sure removing .got is a good idea or not.  Otherwise I observe the
following link error:
powerpc-linux-gnu-ld: warning: orphan section `.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.got'
powerpc-linux-gnu-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc-linux-gnu-ld: final link failed: bad value

sigtramp.c doesn't mention anything from the GOT AFAICT, and doesn't
look like it contains relocations that do, so I'm not sure where
references to _GLOBAL_OFFSET_TABLE_ are coming from.

  arch/powerpc/kernel/vdso32/Makefile     | 7 +++++--
  arch/powerpc/kernel/vdso32/vdso32.lds.S | 3 ++-
  2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile
index 87ab1152d5ce..611a5951945a 100644
--- a/arch/powerpc/kernel/vdso32/Makefile
+++ b/arch/powerpc/kernel/vdso32/Makefile
@@ -27,6 +27,9 @@ UBSAN_SANITIZE := n
  ccflags-y := -shared -fno-common -fno-builtin -nostdlib \
  	-Wl,-soname=linux-vdso32.so.1 -Wl,--hash-style=both
  asflags-y := -D__VDSO32__ -s
+ldflags-y := -shared -soname linux-vdso32.so.1 \
+	$(call ld-option, --eh-frame-hdr) \
+	$(call ld-option, --orphan-handling=warn) -T
  
  obj-y += vdso32_wrapper.o
  extra-y += vdso32.lds
@@ -49,8 +52,8 @@ $(obj-vdso32): %.o: %.S FORCE
  	$(call if_changed_dep,vdso32as)
  
  # actual build commands
-quiet_cmd_vdso32ld = VDSO32L $@
-      cmd_vdso32ld = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ $(call cc-ldoption, -Wl$(comma)--orphan-handling=warn) -Wl,-T$(filter %.lds,$^) $(filter %.o,$^)
+quiet_cmd_vdso32ld = LD      $@
+      cmd_vdso32ld = $(cmd_ld)
  quiet_cmd_vdso32as = VDSO32A $@
        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) -c -o $@ $<
  
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 4c985467a668..0ccdebad18b8 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -61,7 +61,6 @@ SECTIONS
  	.fixup		: { *(.fixup) }
  
  	.dynamic	: { *(.dynamic) }		:text	:dynamic
-	.got		: { *(.got) }			:text
  	.plt		: { *(.plt) }
  
  	_end = .;
@@ -108,7 +107,9 @@ SECTIONS
  	.debug_varnames  0 : { *(.debug_varnames) }
  
  	/DISCARD/	: {
+		*(.got)
  		*(.note.GNU-stack)
+		*(.branch_lt)
  		*(.data .data.* .gnu.linkonce.d.* .sdata*)
  		*(.bss .sbss .dynbss .dynsbss)
  		*(.glink .iplt .plt .rela*)

Re: [PATCH 2/2] powerpc/vdso32: link vdso64 with linker

From: Christophe Leroy <hidden>
Date: 2020-09-02 07:56:31 


On 9/1/20 10:25 PM, Nick Desaulniers wrote:
Rather than invoke the compiler as the driver, use the linker. That way
we can check --orphan-handling=warn support correctly, as cc-ldoption
was removed in
commit 055efab3120b ("kbuild: drop support for cc-ldoption").

Requires dropping the .got section.  I couldn't find how it was used in
the vdso32.

Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Not sure removing .got is a good idea or not.  Otherwise I observe the
following link error:
powerpc-linux-gnu-ld: warning: orphan section `.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.got'
powerpc-linux-gnu-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc-linux-gnu-ld: final link failed: bad value

sigtramp.c doesn't mention anything from the GOT AFAICT, and doesn't
look like it contains relocations that do, so I'm not sure where
references to _GLOBAL_OFFSET_TABLE_ are coming from.
I'm getting the same but only when building for PPC64.
I don't get any reference to sigtramp.o though:

   CALL    scripts/checksyscalls.sh
   CALL    scripts/atomic/check-atomics.sh
   VDSO32A arch/powerpc/kernel/vdso32/sigtramp.o
   VDSO32A arch/powerpc/kernel/vdso32/gettimeofday.o
   VDSO32A arch/powerpc/kernel/vdso32/datapage.o
   VDSO32A arch/powerpc/kernel/vdso32/cacheflush.o
   VDSO32A arch/powerpc/kernel/vdso32/note.o
   VDSO32A arch/powerpc/kernel/vdso32/getcpu.o
   LD      arch/powerpc/kernel/vdso32/vdso32.so.dbg
powerpc64-linux-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc64-linux-ld: final link failed: Bad value

(GCC 8.1, Binutils 2.30)

So it seems that the got section is being created by the linker. Don't 
know why though.


With GCC 10.1, binutils 2.34 I get:

   LDS     arch/powerpc/kernel/vdso32/vdso32.lds
   VDSO32A arch/powerpc/kernel/vdso32/sigtramp.o
   VDSO32A arch/powerpc/kernel/vdso32/gettimeofday.o
   VDSO32A arch/powerpc/kernel/vdso32/datapage.o
   VDSO32A arch/powerpc/kernel/vdso32/cacheflush.o
   VDSO32A arch/powerpc/kernel/vdso32/note.o
   VDSO32A arch/powerpc/kernel/vdso32/getcpu.o
   LD      arch/powerpc/kernel/vdso32/vdso32.so.dbg
powerpc64-linux-ld: warning: orphan section `.branch_lt' from 
`arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.branch_lt'
powerpc64-linux-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc64-linux-ld: final link failed: bad value

I can't see any .branch_lt section when objdumping sigtramp.o or any 
other .o

When I move sigtramp.o at the end of the definition of obj-vdso32 in 
Makefile, I then get:

powerpc64-linux-ld: warning: orphan section `.branch_lt' from 
`arch/powerpc/kernel/vdso32/gettimeofday.o' being placed in section 
`.branch_lt'
powerpc64-linux-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc64-linux-ld: final link failed: bad value


gettimeofday.o now being the first object in obj-vdso32


Christophe
quoted hunk
  arch/powerpc/kernel/vdso32/Makefile     | 7 +++++--
  arch/powerpc/kernel/vdso32/vdso32.lds.S | 3 ++-
  2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/kernel/vdso32/Makefile b/arch/powerpc/kernel/vdso32/Makefile
index 87ab1152d5ce..611a5951945a 100644
--- a/arch/powerpc/kernel/vdso32/Makefile
+++ b/arch/powerpc/kernel/vdso32/Makefile
@@ -27,6 +27,9 @@ UBSAN_SANITIZE := n
  ccflags-y := -shared -fno-common -fno-builtin -nostdlib \
  	-Wl,-soname=linux-vdso32.so.1 -Wl,--hash-style=both
  asflags-y := -D__VDSO32__ -s
+ldflags-y := -shared -soname linux-vdso32.so.1 \
+	$(call ld-option, --eh-frame-hdr) \
+	$(call ld-option, --orphan-handling=warn) -T
  
  obj-y += vdso32_wrapper.o
  extra-y += vdso32.lds
@@ -49,8 +52,8 @@ $(obj-vdso32): %.o: %.S FORCE
  	$(call if_changed_dep,vdso32as)
  
  # actual build commands
-quiet_cmd_vdso32ld = VDSO32L $@
-      cmd_vdso32ld = $(VDSOCC) $(c_flags) $(CC32FLAGS) -o $@ $(call cc-ldoption, -Wl$(comma)--orphan-handling=warn) -Wl,-T$(filter %.lds,$^) $(filter %.o,$^)
+quiet_cmd_vdso32ld = LD      $@
+      cmd_vdso32ld = $(cmd_ld)
  quiet_cmd_vdso32as = VDSO32A $@
        cmd_vdso32as = $(VDSOCC) $(a_flags) $(CC32FLAGS) -c -o $@ $<
  
diff --git a/arch/powerpc/kernel/vdso32/vdso32.lds.S b/arch/powerpc/kernel/vdso32/vdso32.lds.S
index 4c985467a668..0ccdebad18b8 100644
--- a/arch/powerpc/kernel/vdso32/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso32/vdso32.lds.S
@@ -61,7 +61,6 @@ SECTIONS
  	.fixup		: { *(.fixup) }
  
  	.dynamic	: { *(.dynamic) }		:text	:dynamic
-	.got		: { *(.got) }			:text
  	.plt		: { *(.plt) }
  
  	_end = .;
@@ -108,7 +107,9 @@ SECTIONS
  	.debug_varnames  0 : { *(.debug_varnames) }
  
  	/DISCARD/	: {
+		*(.got)
  		*(.note.GNU-stack)
+		*(.branch_lt)
  		*(.data .data.* .gnu.linkonce.d.* .sdata*)
  		*(.bss .sbss .dynbss .dynsbss)
  		*(.glink .iplt .plt .rela*)

Re: [PATCH 2/2] powerpc/vdso32: link vdso64 with linker

From: Christophe Leroy <hidden>
Date: 2020-09-02 10:17:12 


On 9/1/20 10:25 PM, Nick Desaulniers wrote:
Rather than invoke the compiler as the driver, use the linker. That way
we can check --orphan-handling=warn support correctly, as cc-ldoption
was removed in
commit 055efab3120b ("kbuild: drop support for cc-ldoption").

Requires dropping the .got section.  I couldn't find how it was used in
the vdso32.

Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
Not sure removing .got is a good idea or not.  Otherwise I observe the
following link error:
powerpc-linux-gnu-ld: warning: orphan section `.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.got'
powerpc-linux-gnu-ld: _GLOBAL_OFFSET_TABLE_ not defined in linker created .got
powerpc-linux-gnu-ld: final link failed: bad value
Finally I spotted it I think:

	make arch/powerpc/kernel/vdso32/ V=1

powerpc64-linux-ld  -EB -m elf64ppc -shared -soname linux-vdso32.so.1 
--eh-frame-hdr  --orphan-handling=warn -T 
arch/powerpc/kernel/vdso32/vdso32.lds 
arch/powerpc/kernel/vdso32/sigtramp.o 
arch/powerpc/kernel/vdso32/gettimeofday.o 
arch/powerpc/kernel/vdso32/datapage.o 
arch/powerpc/kernel/vdso32/cacheflush.o 
arch/powerpc/kernel/vdso32/note.o arch/powerpc/kernel/vdso32/getcpu.o -o 
arch/powerpc/kernel/vdso32/vdso32.so.dbg



If I do the same manually but with -m elf32ppc instead of -m elf64ppc, 
there is no failure.

Adding -m elf32ppc to ldflags-y also works, allthough I don't like too 
much having "-m elf64ppc -m elf32ppc" on the line.

Christophe

Re: [PATCH 1/2] powerpc/vdso64: link vdso64 with linker

From: Michael Ellerman <mpe@ellerman.id.au>
Date: 2020-09-02 12:14:43 

Nick Desaulniers [off-list ref] writes:
Rather than invoke the compiler as the driver, use the linker. That way
we can check --orphan-handling=warn support correctly, as cc-ldoption
was removed in
commit 055efab3120b ("kbuild: drop support for cc-ldoption").
Ouch.

Seems make is quite happy to $(call deadbeef, ...) and not print a
warning, which I guess is probably a feature.

Painstakingly compared the output between `objdump -a` before and after
this change. Now function symbols have the correct type of FUNC rather
than NONE, and the entry is slightly different (which doesn't matter for
the vdso). Binary size is the same.

Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
I think I'll just revert that for v5.9 ?

cheers
quoted hunk
Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 arch/powerpc/include/asm/vdso.h         | 17 ++---------------
 arch/powerpc/kernel/vdso64/Makefile     |  8 ++++++--
 arch/powerpc/kernel/vdso64/vdso64.lds.S |  1 -
 3 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/include/asm/vdso.h b/arch/powerpc/include/asm/vdso.h
index 2ff884853f97..11b2ecf49f79 100644
--- a/arch/powerpc/include/asm/vdso.h
+++ b/arch/powerpc/include/asm/vdso.h
@@ -24,19 +24,7 @@ int vdso_getcpu_init(void);
 
 #else /* __ASSEMBLY__ */
 
-#ifdef __VDSO64__
-#define V_FUNCTION_BEGIN(name)		\
-	.globl name;			\
-	name:				\
-
-#define V_FUNCTION_END(name)		\
-	.size name,.-name;
-
-#define V_LOCAL_FUNC(name) (name)
-#endif /* __VDSO64__ */
-
-#ifdef __VDSO32__
-
+#if defined(__VDSO32__) || defined (__VDSO64__)
 #define V_FUNCTION_BEGIN(name)		\
 	.globl name;			\
 	.type name,@function; 		\
@@ -46,8 +34,7 @@ int vdso_getcpu_init(void);
 	.size name,.-name;
 
 #define V_LOCAL_FUNC(name) (name)
-
-#endif /* __VDSO32__ */
+#endif /* __VDSO{32|64}__ */
 
 #endif /* __ASSEMBLY__ */
 
diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile
index 38c317f25141..7ea3ce537d0a 100644
--- a/arch/powerpc/kernel/vdso64/Makefile
+++ b/arch/powerpc/kernel/vdso64/Makefile
@@ -32,9 +32,13 @@ $(obj)/%.so: OBJCOPYFLAGS := -S
 $(obj)/%.so: $(obj)/%.so.dbg FORCE
 	$(call if_changed,objcopy)
 
+ldflags-y := -shared -soname linux-vdso64.so.1 \
+	$(call ld-option, --eh-frame-hdr) \
+	$(call ld-option, --orphan-handling=warn) -T
+
 # actual build commands
-quiet_cmd_vdso64ld = VDSO64L $@
-      cmd_vdso64ld = $(CC) $(c_flags) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) $(call cc-ldoption, -Wl$(comma)--orphan-handling=warn)
+quiet_cmd_vdso64ld = LD      $@
+      cmd_vdso64ld = $(cmd_ld)
 
 # install commands for the unstripped file
 quiet_cmd_vdso_install = INSTALL $@
diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S
index 4e3a8d4ee614..58c33b704b6a 100644
--- a/arch/powerpc/kernel/vdso64/vdso64.lds.S
+++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S
@@ -11,7 +11,6 @@ OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle")
 OUTPUT_FORMAT("elf64-powerpc", "elf64-powerpc", "elf64-powerpc")
 #endif
 OUTPUT_ARCH(powerpc:common64)
-ENTRY(_start)
 
 SECTIONS
 {
-- 
2.28.0.402.g5ffc5be6b7-goog

Re: [PATCH 2/2] powerpc/vdso32: link vdso64 with linker

From: Segher Boessenkool <hidden>
Date: 2020-09-02 14:26:07 

Hi!

On Wed, Sep 02, 2020 at 06:46:45AM +0000, Christophe Leroy wrote:
ld crashes:

  LD      arch/powerpc/kernel/vdso32/vdso32.so.dbg
/bin/sh: line 1: 23780 Segmentation fault      (core dumped) 
ppc-linux-ld -EB -m elf32ppc -shared -soname linux-vdso32.so.1 
--eh-frame-hdr --orphan-handling=warn -T 
arch/powerpc/kernel/vdso32/vdso32.lds 
arch/powerpc/kernel/vdso32/sigtramp.o 
arch/powerpc/kernel/vdso32/gettimeofday.o 
arch/powerpc/kernel/vdso32/datapage.o 
arch/powerpc/kernel/vdso32/cacheflush.o 
arch/powerpc/kernel/vdso32/note.o arch/powerpc/kernel/vdso32/getcpu.o -o 
arch/powerpc/kernel/vdso32/vdso32.so.dbg
make[4]: *** [arch/powerpc/kernel/vdso32/vdso32.so.dbg] Error 139


[root@localhost linux-powerpc]# ppc-linux-ld --version
GNU ld (GNU Binutils) 2.26.20160125
[ Don't build as root :-P ]

Try with a newer ld?  If it still happens with current versions, please
open a bug report?  https://sourceware.org/bugzilla


Segher

Re: [PATCH 2/2] powerpc/vdso32: link vdso64 with linker

From: Christophe Leroy <hidden>
Date: 2020-09-02 15:43:40 

Hi,

Le 02/09/2020 à 16:14, Segher Boessenkool a écrit :
Hi!

On Wed, Sep 02, 2020 at 06:46:45AM +0000, Christophe Leroy wrote:
quoted
ld crashes:

   LD      arch/powerpc/kernel/vdso32/vdso32.so.dbg
/bin/sh: line 1: 23780 Segmentation fault      (core dumped)
ppc-linux-ld -EB -m elf32ppc -shared -soname linux-vdso32.so.1
--eh-frame-hdr --orphan-handling=warn -T
arch/powerpc/kernel/vdso32/vdso32.lds
arch/powerpc/kernel/vdso32/sigtramp.o
arch/powerpc/kernel/vdso32/gettimeofday.o
arch/powerpc/kernel/vdso32/datapage.o
arch/powerpc/kernel/vdso32/cacheflush.o
arch/powerpc/kernel/vdso32/note.o arch/powerpc/kernel/vdso32/getcpu.o -o
arch/powerpc/kernel/vdso32/vdso32.so.dbg
make[4]: *** [arch/powerpc/kernel/vdso32/vdso32.so.dbg] Error 139


[root@localhost linux-powerpc]# ppc-linux-ld --version
GNU ld (GNU Binutils) 2.26.20160125
[ Don't build as root :-P ]

Try with a newer ld?  If it still happens with current versions, please
open a bug report?  https://sourceware.org/bugzilla
Yes it works with 2.30 and 2.34
But minimum for building kernel is supposed to be 2.23

Christophe

Re: [PATCH 2/2] powerpc/vdso32: link vdso64 with linker

From: Segher Boessenkool <hidden>
Date: 2020-09-02 16:58:05 

On Wed, Sep 02, 2020 at 05:43:03PM +0200, Christophe Leroy wrote:
quoted
Try with a newer ld?  If it still happens with current versions, please
open a bug report?  https://sourceware.org/bugzilla
Yes it works with 2.30 and 2.34
Ah okay, I missed this part.

But minimum for building kernel is supposed to be 2.23
Sure.  Tthat could be upgraded to 2.24 -- you should use a binutils at
least as new as your GCC, and that requires 4.9 now -- but that
probably doesn't help you here).


Segher

Re: [PATCH 1/2] powerpc/vdso64: link vdso64 with linker

From: Nick Desaulniers <ndesaulniers@google.com>
Date: 2020-09-02 17:41:40 

On Wed, Sep 2, 2020 at 5:14 AM Michael Ellerman [off-list ref] wrote:
Nick Desaulniers [off-list ref] writes:
quoted
Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
I think I'll just revert that for v5.9 ?
SGTM; you'll probably still want these changes with some modifications
at some point; vdso32 did have at least one orphaned section, and will
be important for hermetic builds.  Seeing crashes in supported
versions of the tools ties our hands at the moment.
-- 
Thanks,
~Nick Desaulniers

Re: [PATCH 1/2] powerpc/vdso64: link vdso64 with linker

From: Christophe Leroy <hidden>
Date: 2020-09-02 18:02:37 


Le 02/09/2020 à 19:41, Nick Desaulniers a écrit :
On Wed, Sep 2, 2020 at 5:14 AM Michael Ellerman [off-list ref] wrote:
quoted
Nick Desaulniers [off-list ref] writes:
quoted
Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
I think I'll just revert that for v5.9 ?
SGTM; you'll probably still want these changes with some modifications
at some point; vdso32 did have at least one orphaned section, and will
be important for hermetic builds.  Seeing crashes in supported
versions of the tools ties our hands at the moment.
Keeping the tool problem aside with binutils 2.26, do you have a way to 
really link an elf32ppc object when  building vdso32 for PPC64 ?

Christophe

Re: [PATCH 1/2] powerpc/vdso64: link vdso64 with linker

From: Nick Desaulniers <ndesaulniers@google.com>
Date: 2021-04-22 22:44:18 

On Wed, Sep 2, 2020 at 11:02 AM Christophe Leroy
[off-list ref] wrote:


Le 02/09/2020 à 19:41, Nick Desaulniers a écrit :
quoted
On Wed, Sep 2, 2020 at 5:14 AM Michael Ellerman [off-list ref] wrote:
quoted
Nick Desaulniers [off-list ref] writes:
quoted
Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
I think I'll just revert that for v5.9 ?
SGTM; you'll probably still want these changes with some modifications
at some point; vdso32 did have at least one orphaned section, and will
be important for hermetic builds.  Seeing crashes in supported
versions of the tools ties our hands at the moment.
Keeping the tool problem aside with binutils 2.26, do you have a way to
really link an elf32ppc object when  building vdso32 for PPC64 ?
Sorry, I'm doing a bug scrub and found
https://github.com/ClangBuiltLinux/linux/issues/774 still open (and my
reply to this thread still in Drafts; never sent). With my patches
rebased:
$ file arch/powerpc/kernel/vdso32/vdso32.so
arch/powerpc/kernel/vdso32/vdso32.so: ELF 32-bit MSB shared object,
PowerPC or cisco 4500, version 1 (SYSV), dynamically linked, stripped

Are you still using 2.26?

I'm not able to repro Nathan's reported issue from
https://lore.kernel.org/lkml/20200902052123.GA2687902@ubuntu-n2-xlarge-x86/,
so I'm curious if I should resend the rebased patches as v2?

--
Thanks,
~Nick Desaulniers

Re: [PATCH 1/2] powerpc/vdso64: link vdso64 with linker

From: Christophe Leroy <hidden>
Date: 2021-04-23 07:40:12 


Le 23/04/2021 à 00:44, Nick Desaulniers a écrit :
On Wed, Sep 2, 2020 at 11:02 AM Christophe Leroy
[off-list ref] wrote:
quoted


Le 02/09/2020 à 19:41, Nick Desaulniers a écrit :
quoted
On Wed, Sep 2, 2020 at 5:14 AM Michael Ellerman [off-list ref] wrote:
quoted
Nick Desaulniers [off-list ref] writes:
quoted
Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
I think I'll just revert that for v5.9 ?
SGTM; you'll probably still want these changes with some modifications
at some point; vdso32 did have at least one orphaned section, and will
be important for hermetic builds.  Seeing crashes in supported
versions of the tools ties our hands at the moment.
Keeping the tool problem aside with binutils 2.26, do you have a way to
really link an elf32ppc object when  building vdso32 for PPC64 ?
Sorry, I'm doing a bug scrub and found
https://github.com/ClangBuiltLinux/linux/issues/774 still open (and my
reply to this thread still in Drafts; never sent). With my patches
rebased:
$ file arch/powerpc/kernel/vdso32/vdso32.so
arch/powerpc/kernel/vdso32/vdso32.so: ELF 32-bit MSB shared object,
PowerPC or cisco 4500, version 1 (SYSV), dynamically linked, stripped

Are you still using 2.26?
Yes, our production kernels and applications are built with gcc 5.5 and binutils 2.26

I'm not able to repro Nathan's reported issue from
https://lore.kernel.org/lkml/20200902052123.GA2687902@ubuntu-n2-xlarge-x86/,
so I'm curious if I should resend the rebased patches as v2?
I can't remember what was all this discussion about.

I gave a try to your rebased patches.

Still an issue with binutils 2.26:

   VDSO32L arch/powerpc/kernel/vdso32/vdso32.so.dbg
ppc-linux-ld: warning: orphan section `.rela.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' being 
placed in section `.rela.dyn'.
ppc-linux-ld: warning: orphan section `.rela.plt' from `arch/powerpc/kernel/vdso32/sigtramp.o' being 
placed in section `.rela.dyn'.
ppc-linux-ld: warning: orphan section `.glink' from `arch/powerpc/kernel/vdso32/sigtramp.o' being 
placed in section `.glink'.
ppc-linux-ld: warning: orphan section `.iplt' from `arch/powerpc/kernel/vdso32/sigtramp.o' being 
placed in section `.iplt'.
ppc-linux-ld: warning: orphan section `.rela.iplt' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.rela.dyn'.
ppc-linux-ld: warning: orphan section `.rela.text' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.rela.dyn'.
/bin/sh: line 1:  7850 Segmentation fault      (core dumped) ppc-linux-ld -EB -m elf32ppc -shared 
-soname linux-vdso32.so.1 --eh-frame-hdr --orphan-handling=warn -T 
arch/powerpc/kernel/vdso32/vdso32.lds arch/powerpc/kernel/vdso32/sigtramp.o 
arch/powerpc/kernel/vdso32/gettimeofday.o arch/powerpc/kernel/vdso32/datapage.o 
arch/powerpc/kernel/vdso32/cacheflush.o arch/powerpc/kernel/vdso32/note.o 
arch/powerpc/kernel/vdso32/getcpu.o arch/powerpc/kernel/vdso32/vgettimeofday.o -o 
arch/powerpc/kernel/vdso32/vdso32.so.dbg
make[2]: *** [arch/powerpc/kernel/vdso32/vdso32.so.dbg] Error 139
make[2]: *** Deleting file `arch/powerpc/kernel/vdso32/vdso32.so.dbg'



With gcc 10.1 and binutils 2.34 I get:

PPC32 build:

   VDSO32L arch/powerpc/kernel/vdso32/vdso32.so.dbg
powerpc64-linux-ld: warning: orphan section `.rela.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.plt' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.glink' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.glink'
powerpc64-linux-ld: warning: orphan section `.iplt' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.iplt'
powerpc64-linux-ld: warning: orphan section `.rela.iplt' from 
`arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.branch_lt' from 
`arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.text' from 
`arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.rela.dyn'


PPC64 build:

   VDSO32L arch/powerpc/kernel/vdso32/vdso32.so.dbg
powerpc64-linux-ld: warning: orphan section `.rela.got' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.plt' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.glink' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.glink'
powerpc64-linux-ld: warning: orphan section `.iplt' from `arch/powerpc/kernel/vdso32/sigtramp.o' 
being placed in section `.iplt'
powerpc64-linux-ld: warning: orphan section `.rela.iplt' from 
`arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.branch_lt' from 
`arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.text' from 
`arch/powerpc/kernel/vdso32/sigtramp.o' being placed in section `.rela.dyn'
   VDSOSYM include/generated/vdso32-offsets.h
   VDSO64L arch/powerpc/kernel/vdso64/vdso64.so.dbg
powerpc64-linux-ld: warning: orphan section `.iplt' from `linker stubs' being placed in section `.iplt'
powerpc64-linux-ld: warning: orphan section `.rela.iplt' from `linker stubs' being placed in section 
`.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.branch_lt' from `linker stubs' being placed in 
section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.branch_lt' from `linker stubs' being placed in 
section `.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.plt' from `linker stubs' being placed in section `.plt'
powerpc64-linux-ld: warning: orphan section `.rela.plt' from `linker stubs' being placed in section 
`.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.got' from `linker stubs' being placed in section 
`.rela.dyn'
powerpc64-linux-ld: warning: orphan section `.rela.opd' from `linker stubs' being placed in section 
`.rela.dyn'


Christophe

Re: [PATCH 1/2] powerpc/vdso64: link vdso64 with linker

From: Christophe Leroy <hidden>
Date: 2021-04-23 17:18:44 


Le 23/04/2021 à 00:44, Nick Desaulniers a écrit :
On Wed, Sep 2, 2020 at 11:02 AM Christophe Leroy
[off-list ref] wrote:
quoted


Le 02/09/2020 à 19:41, Nick Desaulniers a écrit :
quoted
On Wed, Sep 2, 2020 at 5:14 AM Michael Ellerman [off-list ref] wrote:
quoted
Nick Desaulniers [off-list ref] writes:
quoted
Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
I think I'll just revert that for v5.9 ?
SGTM; you'll probably still want these changes with some modifications
at some point; vdso32 did have at least one orphaned section, and will
be important for hermetic builds.  Seeing crashes in supported
versions of the tools ties our hands at the moment.
Keeping the tool problem aside with binutils 2.26, do you have a way to
really link an elf32ppc object when  building vdso32 for PPC64 ?
Sorry, I'm doing a bug scrub and found
https://github.com/ClangBuiltLinux/linux/issues/774 still open (and my
reply to this thread still in Drafts; never sent). With my patches
rebased:
$ file arch/powerpc/kernel/vdso32/vdso32.so
arch/powerpc/kernel/vdso32/vdso32.so: ELF 32-bit MSB shared object,
PowerPC or cisco 4500, version 1 (SYSV), dynamically linked, stripped

Are you still using 2.26?

I'm not able to repro Nathan's reported issue from
https://lore.kernel.org/lkml/20200902052123.GA2687902@ubuntu-n2-xlarge-x86/,
so I'm curious if I should resend the rebased patches as v2?
One comment on your rebased patch:

 > diff --git a/arch/powerpc/include/asm/vdso.h b/arch/powerpc/include/asm/vdso.h
 > index 8542e9bbeead..0bd06ec06aaa 100644
 > --- a/arch/powerpc/include/asm/vdso.h
 > +++ b/arch/powerpc/include/asm/vdso.h
 > @@ -25,19 +25,7 @@ int vdso_getcpu_init(void);
 >
 >   #else /* __ASSEMBLY__ */
 >
 > -#ifdef __VDSO64__
 > -#define V_FUNCTION_BEGIN(name)		\
 > -	.globl name;			\
 > -	name:				\
 > -
 > -#define V_FUNCTION_END(name)		\
 > -	.size name,.-name;
 > -
 > -#define V_LOCAL_FUNC(name) (name)
 > -#endif /* __VDSO64__ */
 > -
 > -#ifdef __VDSO32__
 > -
 > +#if defined(__VDSO32__) || defined (__VDSO64__)

You always have either __VDSO32__ or __VDSO64__ so this #if is pointless

 >   #define V_FUNCTION_BEGIN(name)		\
 >   	.globl name;			\
 >   	.type name,@function; 		\
 > @@ -47,8 +35,7 @@ int vdso_getcpu_init(void);
 >   	.size name,.-name;
 >
 >   #define V_LOCAL_FUNC(name) (name)
 > -
 > -#endif /* __VDSO32__ */
 > +#endif /* __VDSO{32|64}__ */
 >
 >   #endif /* __ASSEMBLY__ */
 >


Christophe

Re: [PATCH 1/2] powerpc/vdso64: link vdso64 with linker

From: Christophe Leroy <hidden>
Date: 2022-03-02 16:48:09 


Le 02/09/2020 à 00:25, Nick Desaulniers a écrit :
Rather than invoke the compiler as the driver, use the linker. That way
we can check --orphan-handling=warn support correctly, as cc-ldoption
was removed in
commit 055efab3120b ("kbuild: drop support for cc-ldoption").

Painstakingly compared the output between `objdump -a` before and after
this change. Now function symbols have the correct type of FUNC rather
than NONE, and the entry is slightly different (which doesn't matter for
the vdso). Binary size is the same.

Fixes: commit f2af201002a8 ("powerpc/build: vdso linker warning for orphan sections")
Link: https://lore.kernel.org/lkml/CAKwvOdnn3wxYdJomvnveyD_njwRku3fABWT_bS92duihhywLJQ@mail.gmail.com/
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Is this change still necessary ? If so please rebase as we have changed 
the structure of VDSO source files (Only one directory common to 32 and 64).

Christophe
quoted hunk
---
  arch/powerpc/include/asm/vdso.h         | 17 ++---------------
  arch/powerpc/kernel/vdso64/Makefile     |  8 ++++++--
  arch/powerpc/kernel/vdso64/vdso64.lds.S |  1 -
  3 files changed, 8 insertions(+), 18 deletions(-)

diff --git a/arch/powerpc/include/asm/vdso.h b/arch/powerpc/include/asm/vdso.h
index 2ff884853f97..11b2ecf49f79 100644
--- a/arch/powerpc/include/asm/vdso.h
+++ b/arch/powerpc/include/asm/vdso.h
@@ -24,19 +24,7 @@ int vdso_getcpu_init(void);
  
  #else /* __ASSEMBLY__ */
  
-#ifdef __VDSO64__
-#define V_FUNCTION_BEGIN(name)		\
-	.globl name;			\
-	name:				\
-
-#define V_FUNCTION_END(name)		\
-	.size name,.-name;
-
-#define V_LOCAL_FUNC(name) (name)
-#endif /* __VDSO64__ */
-
-#ifdef __VDSO32__
-
+#if defined(__VDSO32__) || defined (__VDSO64__)
  #define V_FUNCTION_BEGIN(name)		\
  	.globl name;			\
  	.type name,@function; 		\
@@ -46,8 +34,7 @@ int vdso_getcpu_init(void);
  	.size name,.-name;
  
  #define V_LOCAL_FUNC(name) (name)
-
-#endif /* __VDSO32__ */
+#endif /* __VDSO{32|64}__ */
  
  #endif /* __ASSEMBLY__ */
  
diff --git a/arch/powerpc/kernel/vdso64/Makefile b/arch/powerpc/kernel/vdso64/Makefile
index 38c317f25141..7ea3ce537d0a 100644
--- a/arch/powerpc/kernel/vdso64/Makefile
+++ b/arch/powerpc/kernel/vdso64/Makefile
@@ -32,9 +32,13 @@ $(obj)/%.so: OBJCOPYFLAGS := -S
  $(obj)/%.so: $(obj)/%.so.dbg FORCE
  	$(call if_changed,objcopy)
  
+ldflags-y := -shared -soname linux-vdso64.so.1 \
+	$(call ld-option, --eh-frame-hdr) \
+	$(call ld-option, --orphan-handling=warn) -T
+
  # actual build commands
-quiet_cmd_vdso64ld = VDSO64L $@
-      cmd_vdso64ld = $(CC) $(c_flags) -o $@ -Wl,-T$(filter %.lds,$^) $(filter %.o,$^) $(call cc-ldoption, -Wl$(comma)--orphan-handling=warn)
+quiet_cmd_vdso64ld = LD      $@
+      cmd_vdso64ld = $(cmd_ld)
  
  # install commands for the unstripped file
  quiet_cmd_vdso_install = INSTALL $@
diff --git a/arch/powerpc/kernel/vdso64/vdso64.lds.S b/arch/powerpc/kernel/vdso64/vdso64.lds.S
index 4e3a8d4ee614..58c33b704b6a 100644
--- a/arch/powerpc/kernel/vdso64/vdso64.lds.S
+++ b/arch/powerpc/kernel/vdso64/vdso64.lds.S
@@ -11,7 +11,6 @@ OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle")
  OUTPUT_FORMAT("elf64-powerpc", "elf64-powerpc", "elf64-powerpc")
  #endif
  OUTPUT_ARCH(powerpc:common64)
-ENTRY(_start)
  
  SECTIONS
  {
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