| Message ID | 1459455040-25671-1-git-send-email-bauerman@linux.vnet.ibm.com (mailing list archive) |
|---|---|
| State | Accepted |
| Headers | show |
Hello, People seem to be considering patches for next, so this looks like a good moment to ping about this one.
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 <ananth@in.ibm.com> > Cc: Michael Ellerman <mpe@ellerman.id.au> > Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> > Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/61ed9cfb1b0951a3b4b98dd8bf cheers
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
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 <ananth@in.ibm.com> Cc: Michael Ellerman <mpe@ellerman.id.au> Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com> --- arch/powerpc/kernel/kprobes.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-)