Fixes the following testsuite failure:
$ sudo ./perf test -v kallsyms
1: vmlinux symtab matches kallsyms :
--- start ---
test child forked, pid 12489
Using /proc/kcore for kernel object code
Looking at the vmlinux_path (8 entries long)
Using /boot/vmlinux for symbols
0xc00000000003d300: diff name v: .kretprobe_trampoline_holder k: kretprobe_trampoline
Maps only in vmlinux:
c00000000086ca38-c000000000879b6c 87ca38 [kernel].text.unlikely
c000000000879b6c-c000000000bf0000 889b6c [kernel].meminit.text
c000000000bf0000-c000000000c53264 c00000 [kernel].init.text
c000000000c53264-d000000004250000 c63264 [kernel].exit.text
d000000004250000-d000000004450000 0 [libcrc32c]
d000000004450000-d000000004620000 0 [xfs]
d000000004620000-d000000004680000 0 [autofs4]
d000000004680000-d0000000046e0000 0 [x_tables]
d0000000046e0000-d000000004780000 0 [ip_tables]
d000000004780000-d0000000047e0000 0 [rng_core]
d0000000047e0000-ffffffffffffffff 0 [pseries_rng]
Maps in vmlinux with a different name in kallsyms:
Maps only in kallsyms:
d000000000000000-f000000000000000 1000000000010000 [kernel.kallsyms]
f000000000000000-ffffffffffffffff 3000000000010000 [kernel.kallsyms]
test child finished with -1
---- end ----
vmlinux symtab matches kallsyms: FAILED!
The problem is that the kretprobe_trampoline symbol looks like this:
$ eu-readelf -s /boot/vmlinux G kretprobe_trampoline
2431: c000000001302368 24 NOTYPE LOCAL DEFAULT 37 kretprobe_trampoline_holder
2432: c00000000003d300 8 FUNC LOCAL DEFAULT 1 .kretprobe_trampoline_holder
97543: c00000000003d300 0 NOTYPE GLOBAL DEFAULT 1 kretprobe_trampoline
Its type is NOTYPE, and its size is 0, and this is a problem because
symbol-elf.c:dso__load_sym skips function symbols that are not STT_FUNC
or STT_GNU_IFUNC (this is determined by elf_sym__is_function). Even
if the type is changed to STT_FUNC, when dso__load_sym calls
symbols__fixup_duplicate, the kretprobe_trampoline symbol is dropped in
favour of .kretprobe_trampoline_holder because the latter has non-zero
size (as determined by choose_best_symbol).
With this patch, all vmlinux symbols match /proc/kallsyms and the
testcase passes.
Commit c1c355ce14c0 ("x86/kprobes: Get rid of
kretprobe_trampoline_holder()") gets rid of kretprobe_trampoline_holder
altogether on x86. This commit does the same on powerpc. This change
introduces no regressions on the perf and ftracetest testsuite results.
Cc: Ananth N Mavinakayanahalli <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Naveen N. Rao <redacted>
Signed-off-by: Thiago Jung Bauermann <redacted>
---
arch/powerpc/kernel/kprobes.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c
index 7c053f281406..417c0eadd094 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -278,12 +278,11 @@ no_kprobe:
* - When the probed function returns, this probe
* causes the handlers to fire
*/
-static void __used kretprobe_trampoline_holder(void)
-{
- asm volatile(".global kretprobe_trampoline\n"
- "kretprobe_trampoline:\n"
- "nop\n");
-}
+asm(".global kretprobe_trampoline\n"
+ ".type kretprobe_trampoline, @function\n"
+ "kretprobe_trampoline:\n"
+ "nop\n"
+ ".size kretprobe_trampoline, .-kretprobe_trampoline\n");
/*
* Called when the probe at kretprobe trampoline is hit--
1.9.1
Hello,
People seem to be considering patches for next, so this looks like a go=
od=20
moment to ping about this one.
--=20
[]'s
Thiago Jung Bauermann
IBM Linux Technology Center
Am Donnerstag, 31 M=E4rz 2016, 17:10:40 schrieb Thiago Jung Bauermann:
Fixes the following testsuite failure:
=20
$ sudo ./perf test -v kallsyms
1: vmlinux symtab matches kallsyms :
--- start ---
test child forked, pid 12489
Using /proc/kcore for kernel object code
Looking at the vmlinux_path (8 entries long)
Using /boot/vmlinux for symbols
0xc00000000003d300: diff name v: .kretprobe_trampoline_holder k:
kretprobe_trampoline Maps only in vmlinux:
c00000000086ca38-c000000000879b6c 87ca38 [kernel].text.unlikely
c000000000879b6c-c000000000bf0000 889b6c [kernel].meminit.text
c000000000bf0000-c000000000c53264 c00000 [kernel].init.text
c000000000c53264-d000000004250000 c63264 [kernel].exit.text
d000000004250000-d000000004450000 0 [libcrc32c]
d000000004450000-d000000004620000 0 [xfs]
d000000004620000-d000000004680000 0 [autofs4]
d000000004680000-d0000000046e0000 0 [x_tables]
d0000000046e0000-d000000004780000 0 [ip_tables]
d000000004780000-d0000000047e0000 0 [rng_core]
d0000000047e0000-ffffffffffffffff 0 [pseries_rng]
Maps in vmlinux with a different name in kallsyms:
Maps only in kallsyms:
d000000000000000-f000000000000000 1000000000010000 [kernel.kallsym=
s]
f000000000000000-ffffffffffffffff 3000000000010000 [kernel.kallsym=
s]
test child finished with -1
---- end ----
vmlinux symtab matches kallsyms: FAILED!
=20
The problem is that the kretprobe_trampoline symbol looks like this:
=20
$ eu-readelf -s /boot/vmlinux G kretprobe_trampoline
2431: c000000001302368 24 NOTYPE LOCAL DEFAULT 37
kretprobe_trampoline_holder 2432: c00000000003d300 8 FUNC LOC=
AL=20
DEFAULT 1 .kretprobe_trampoline_holder 97543: c00000000003d300=
=20
0 NOTYPE GLOBAL DEFAULT 1 kretprobe_trampoline
=20
Its type is NOTYPE, and its size is 0, and this is a problem because
symbol-elf.c:dso__load_sym skips function symbols that are not STT_FU=
NC
or STT_GNU_IFUNC (this is determined by elf_sym__is_function). Even
if the type is changed to STT_FUNC, when dso__load_sym calls
symbols__fixup_duplicate, the kretprobe_trampoline symbol is dropped =
in
favour of .kretprobe_trampoline_holder because the latter has non-zer=
o
size (as determined by choose_best_symbol).
=20
With this patch, all vmlinux symbols match /proc/kallsyms and the
testcase passes.
=20
Commit c1c355ce14c0 ("x86/kprobes: Get rid of
kretprobe_trampoline_holder()") gets rid of kretprobe_trampoline_hold=
er
altogether on x86. This commit does the same on powerpc. This change
introduces no regressions on the perf and ftracetest testsuite result=
s.
quoted hunk
=20
Cc: Ananth N Mavinakayanahalli <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Naveen N. Rao <redacted>
Signed-off-by: Thiago Jung Bauermann <redacted>
---
arch/powerpc/kernel/kprobes.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
=20
diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kpro=
bes.c
quoted hunk
index 7c053f281406..417c0eadd094 100644
--- a/arch/powerpc/kernel/kprobes.c
+++ b/arch/powerpc/kernel/kprobes.c
@@ -278,12 +278,11 @@ no_kprobe:
* =09- When the probed function returns, this probe
* =09=09causes the handlers to fire
*/
-static void __used kretprobe_trampoline_holder(void)
-{
-=09asm volatile(".global kretprobe_trampoline\n"
-=09=09=09"kretprobe_trampoline:\n"
-=09=09=09"nop\n");
-}
+asm(".global kretprobe_trampoline\n"
+=09".type kretprobe_trampoline, @function\n"
+=09"kretprobe_trampoline:\n"
+=09"nop\n"
+=09".size kretprobe_trampoline, .-kretprobe_trampoline\n");=20
/*
* Called when the probe at kretprobe trampoline is hit
On Thu, 2016-31-03 at 20:10:40 UTC, Thiago Jung Bauermann wrote:
Fixes the following testsuite failure:
$ sudo ./perf test -v kallsyms
1: vmlinux symtab matches kallsyms :
--- start ---
test child forked, pid 12489
Using /proc/kcore for kernel object code
Looking at the vmlinux_path (8 entries long)
Using /boot/vmlinux for symbols
0xc00000000003d300: diff name v: .kretprobe_trampoline_holder k: kretprobe_trampoline
Maps only in vmlinux:
c00000000086ca38-c000000000879b6c 87ca38 [kernel].text.unlikely
c000000000879b6c-c000000000bf0000 889b6c [kernel].meminit.text
c000000000bf0000-c000000000c53264 c00000 [kernel].init.text
c000000000c53264-d000000004250000 c63264 [kernel].exit.text
d000000004250000-d000000004450000 0 [libcrc32c]
d000000004450000-d000000004620000 0 [xfs]
d000000004620000-d000000004680000 0 [autofs4]
d000000004680000-d0000000046e0000 0 [x_tables]
d0000000046e0000-d000000004780000 0 [ip_tables]
d000000004780000-d0000000047e0000 0 [rng_core]
d0000000047e0000-ffffffffffffffff 0 [pseries_rng]
Maps in vmlinux with a different name in kallsyms:
Maps only in kallsyms:
d000000000000000-f000000000000000 1000000000010000 [kernel.kallsyms]
f000000000000000-ffffffffffffffff 3000000000010000 [kernel.kallsyms]
test child finished with -1
---- end ----
vmlinux symtab matches kallsyms: FAILED!
The problem is that the kretprobe_trampoline symbol looks like this:
$ eu-readelf -s /boot/vmlinux G kretprobe_trampoline
2431: c000000001302368 24 NOTYPE LOCAL DEFAULT 37 kretprobe_trampoline_holder
2432: c00000000003d300 8 FUNC LOCAL DEFAULT 1 .kretprobe_trampoline_holder
97543: c00000000003d300 0 NOTYPE GLOBAL DEFAULT 1 kretprobe_trampoline
Its type is NOTYPE, and its size is 0, and this is a problem because
symbol-elf.c:dso__load_sym skips function symbols that are not STT_FUNC
or STT_GNU_IFUNC (this is determined by elf_sym__is_function). Even
if the type is changed to STT_FUNC, when dso__load_sym calls
symbols__fixup_duplicate, the kretprobe_trampoline symbol is dropped in
favour of .kretprobe_trampoline_holder because the latter has non-zero
size (as determined by choose_best_symbol).
With this patch, all vmlinux symbols match /proc/kallsyms and the
testcase passes.
Commit c1c355ce14c0 ("x86/kprobes: Get rid of
kretprobe_trampoline_holder()") gets rid of kretprobe_trampoline_holder
altogether on x86. This commit does the same on powerpc. This change
introduces no regressions on the perf and ftracetest testsuite results.
Cc: Ananth N Mavinakayanahalli <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Naveen N. Rao <redacted>
Signed-off-by: Thiago Jung Bauermann <redacted>
Applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/61ed9cfb1b0951a3b4b98dd8bf
cheers