[PATCH v2] powerpc: Allow relative pointers in bug table entries

Subsystems: linux for powerpc (32-bit and 64-bit), the rest

STALE2097d LANDED

Landed in mainline as 1baa1f70ef77 on 2020-12-03.

3 messages, 3 authors, 2020-12-10 · open the first message on its own page

[PATCH v2] powerpc: Allow relative pointers in bug table entries

From: Jordan Niethe <hidden>
Date: 2020-12-01 00:53:59

This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
offsets are stored in the bug entries rather than 64-bit pointers.
While this doesn't save space for 32-bit machines, use it anyway so
there is only one code path.

Signed-off-by: Jordan Niethe <redacted>
---
v2: Remove non-relative pointers code
---
 arch/powerpc/Kconfig           | 4 ++++
 arch/powerpc/include/asm/bug.h | 8 ++++----
 arch/powerpc/xmon/xmon.c       | 4 ++--
 3 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e9f13fe08492..294108e0e5c6 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -311,6 +311,10 @@ config GENERIC_BUG
 	default y
 	depends on BUG
 
+config GENERIC_BUG_RELATIVE_POINTERS
+	def_bool y
+	depends on GENERIC_BUG
+
 config SYS_SUPPORTS_APM_EMULATION
 	default y if PMAC_APM_EMU
 	bool
diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 338f36cd9934..ba0500872cce 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -12,7 +12,7 @@
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 .macro EMIT_BUG_ENTRY addr,file,line,flags
 	 .section __bug_table,"aw"
-5001:	 PPC_LONG \addr, 5002f
+5001:	 .4byte \addr - 5001b, 5002f - 5001b
 	 .short \line, \flags
 	 .org 5001b+BUG_ENTRY_SIZE
 	 .previous
@@ -23,7 +23,7 @@
 #else
 .macro EMIT_BUG_ENTRY addr,file,line,flags
 	 .section __bug_table,"aw"
-5001:	 PPC_LONG \addr
+5001:	 .4byte \addr - 5001b
 	 .short \flags
 	 .org 5001b+BUG_ENTRY_SIZE
 	 .previous
@@ -36,14 +36,14 @@
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 #define _EMIT_BUG_ENTRY				\
 	".section __bug_table,\"aw\"\n"		\
-	"2:\t" PPC_LONG "1b, %0\n"		\
+	"2:\t.4byte 1b - 2b, %0 - 2b\n"		\
 	"\t.short %1, %2\n"			\
 	".org 2b+%3\n"				\
 	".previous\n"
 #else
 #define _EMIT_BUG_ENTRY				\
 	".section __bug_table,\"aw\"\n"		\
-	"2:\t" PPC_LONG "1b\n"			\
+	"2:\t.4byte 1b - 2b\n"			\
 	"\t.short %2\n"				\
 	".org 2b+%3\n"				\
 	".previous\n"
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 55c43a6c9111..9704c81aff7d 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -1745,9 +1745,9 @@ static void print_bug_trap(struct pt_regs *regs)
 
 #ifdef CONFIG_DEBUG_BUGVERBOSE
 	printf("kernel BUG at %s:%u!\n",
-	       bug->file, bug->line);
+	       (char *)bug + bug->file_disp, bug->line);
 #else
-	printf("kernel BUG at %px!\n", (void *)bug->bug_addr);
+	printf("kernel BUG at %px!\n", (void *)bug + bug->bug_addr_disp);
 #endif
 #endif /* CONFIG_BUG */
 }
-- 
2.17.1

Re: [PATCH v2] powerpc: Allow relative pointers in bug table entries

From: Christophe Leroy <hidden>
Date: 2020-12-01 06:27:45


Le 01/12/2020 à 01:52, Jordan Niethe a écrit :
This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
offsets are stored in the bug entries rather than 64-bit pointers.
While this doesn't save space for 32-bit machines, use it anyway so
there is only one code path.

Signed-off-by: Jordan Niethe <redacted>
Reviewed-by: Christophe Leroy <redacted>
Tested-by: Christophe Leroy <redacted> # on PPC32
quoted hunk
---
v2: Remove non-relative pointers code
---
  arch/powerpc/Kconfig           | 4 ++++
  arch/powerpc/include/asm/bug.h | 8 ++++----
  arch/powerpc/xmon/xmon.c       | 4 ++--
  3 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index e9f13fe08492..294108e0e5c6 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -311,6 +311,10 @@ config GENERIC_BUG
  	default y
  	depends on BUG
  
+config GENERIC_BUG_RELATIVE_POINTERS
+	def_bool y
+	depends on GENERIC_BUG
+
  config SYS_SUPPORTS_APM_EMULATION
  	default y if PMAC_APM_EMU
  	bool
diff --git a/arch/powerpc/include/asm/bug.h b/arch/powerpc/include/asm/bug.h
index 338f36cd9934..ba0500872cce 100644
--- a/arch/powerpc/include/asm/bug.h
+++ b/arch/powerpc/include/asm/bug.h
@@ -12,7 +12,7 @@
  #ifdef CONFIG_DEBUG_BUGVERBOSE
  .macro EMIT_BUG_ENTRY addr,file,line,flags
  	 .section __bug_table,"aw"
-5001:	 PPC_LONG \addr, 5002f
+5001:	 .4byte \addr - 5001b, 5002f - 5001b
  	 .short \line, \flags
  	 .org 5001b+BUG_ENTRY_SIZE
  	 .previous
@@ -23,7 +23,7 @@
  #else
  .macro EMIT_BUG_ENTRY addr,file,line,flags
  	 .section __bug_table,"aw"
-5001:	 PPC_LONG \addr
+5001:	 .4byte \addr - 5001b
  	 .short \flags
  	 .org 5001b+BUG_ENTRY_SIZE
  	 .previous
@@ -36,14 +36,14 @@
  #ifdef CONFIG_DEBUG_BUGVERBOSE
  #define _EMIT_BUG_ENTRY				\
  	".section __bug_table,\"aw\"\n"		\
-	"2:\t" PPC_LONG "1b, %0\n"		\
+	"2:\t.4byte 1b - 2b, %0 - 2b\n"		\
  	"\t.short %1, %2\n"			\
  	".org 2b+%3\n"				\
  	".previous\n"
  #else
  #define _EMIT_BUG_ENTRY				\
  	".section __bug_table,\"aw\"\n"		\
-	"2:\t" PPC_LONG "1b\n"			\
+	"2:\t.4byte 1b - 2b\n"			\
  	"\t.short %2\n"				\
  	".org 2b+%3\n"				\
  	".previous\n"
diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 55c43a6c9111..9704c81aff7d 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -1745,9 +1745,9 @@ static void print_bug_trap(struct pt_regs *regs)
  
  #ifdef CONFIG_DEBUG_BUGVERBOSE
  	printf("kernel BUG at %s:%u!\n",
-	       bug->file, bug->line);
+	       (char *)bug + bug->file_disp, bug->line);
  #else
-	printf("kernel BUG at %px!\n", (void *)bug->bug_addr);
+	printf("kernel BUG at %px!\n", (void *)bug + bug->bug_addr_disp);
  #endif
  #endif /* CONFIG_BUG */
  }

Re: [PATCH v2] powerpc: Allow relative pointers in bug table entries

From: Michael Ellerman <hidden>
Date: 2020-12-10 13:53:55

On Tue, 1 Dec 2020 11:52:03 +1100, Jordan Niethe wrote:
This enables GENERIC_BUG_RELATIVE_POINTERS on Power so that 32-bit
offsets are stored in the bug entries rather than 64-bit pointers.
While this doesn't save space for 32-bit machines, use it anyway so
there is only one code path.
Applied to powerpc/next.

[1/1] powerpc: Allow relative pointers in bug table entries
      https://git.kernel.org/powerpc/c/1baa1f70ef77c4447628992ad50ab83213e2eb6c

cheers
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