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Josh Poimboeuf efdb4167e6 scripts/faddr2line: Fix "size mismatch" error

I'm not sure how we missed this problem before.  When I take a function
address and size from an oops and give it to faddr2line, it usually
complains about a size mismatch:

  $ scripts/faddr2line ~/k/vmlinux write_sysrq_trigger+0x51/0x60
  skipping write_sysrq_trigger address at 0xffffffff815731a1 due to size mismatch (0x60 != 83)
  no match for write_sysrq_trigger+0x51/0x60

The problem is caused by differences in how kallsyms and faddr2line
determine a function's size.

kallsyms calculates a function's size by parsing the output of 'nm -n'
and subtracting the next function's address from the current function's
address.  This means that nop instructions after the end of the function
are included in the size.

In contrast, faddr2line reads the size from the symbol table, which does
*not* include the ending nops in the function's size.

Change faddr2line to calculate the size from the output of 'nm -n' to be
consistent with kallsyms and oops outputs.

Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/bd313ed7c4003f6b1fda63e825325c44a9d837de.1477405374.git.jpoimboe@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

2016-10-25 18:40:37 +02:00

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#!/bin/bash

Translate stack dump function offsets.

addr2line doesn't work with KASLR addresses. This works similarly to

addr2line, but instead takes the 'func+0x123' format as input:

$ ./scripts/faddr2line ~/k/vmlinux meminfo_proc_show+0x5/0x568

meminfo_proc_show+0x5/0x568:

meminfo_proc_show at fs/proc/meminfo.c:27

If the address is part of an inlined function, the full inline call chain is

printed:

$ ./scripts/faddr2line ~/k/vmlinux native_write_msr+0x6/0x27

native_write_msr+0x6/0x27:

arch_static_branch at arch/x86/include/asm/msr.h:121

(inlined by) static_key_false at include/linux/jump_label.h:125

(inlined by) native_write_msr at arch/x86/include/asm/msr.h:125

The function size after the '/' in the input is optional, but recommended.

It's used to help disambiguate any duplicate symbol names, which can occur

rarely. If the size is omitted for a duplicate symbol then it's possible for

multiple code sites to be printed:

$ ./scripts/faddr2line ~/k/vmlinux raw_ioctl+0x5

raw_ioctl+0x5/0x20:

raw_ioctl at drivers/char/raw.c:122

raw_ioctl+0x5/0xb1:

raw_ioctl at net/ipv4/raw.c:876

Multiple addresses can be specified on a single command line:

$ ./scripts/faddr2line ~/k/vmlinux type_show+0x10/45 free_reserved_area+0x90

type_show+0x10/0x2d:

type_show at drivers/video/backlight/backlight.c:213

free_reserved_area+0x90/0x123:

free_reserved_area at mm/page_alloc.c:6429 (discriminator 2)

set -o errexit set -o nounset

command -v awk >/dev/null 2>&1 || die "awk isn't installed" command -v readelf >/dev/null 2>&1 || die "readelf isn't installed" command -v addr2line >/dev/null 2>&1 || die "addr2line isn't installed"

usage() { echo "usage: faddr2line

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