redonkable
/
alistair23-linux
1
0
Fork 0
Code Releases Activity

perf report: Fix module symbol adjustment for s390x 

The 'perf report' tool does not display the addresses of kernel module
symbols correctly.

For example symbol qeth_send_ipa_cmd in kernel module qeth.ko has this
relative address for function qeth_send_ipa_cmd():

  [root@s8360047 linux]# nm -g drivers/s390/net/qeth.ko | fgrep send_ipa_cmd
  0000000000013088 T qeth_send_ipa_cmd

The module is loaded at address:

  [root@s8360047 linux]# cat /sys/module/qeth/sections/.text
  0x000003ff80296d20
  [root@s8360047 linux]#

This should result in a start address of:

  0x13088 + 0x3ff80296d20 = 0x3ff802a9da8

Using crash to verify the address on a live system:

  [root@s8360046 linux]# crash vmlinux

  crash 7.1.9++
  Copyright (C) 2002-2016  Red Hat, Inc.
  Copyright (C) 2004, 2005, 2006, 2010  IBM Corporation

  [...]

  crash> mod -s qeth drivers/s390/net/qeth.ko
       MODULE       NAME        SIZE  OBJECT FILE
       3ff8028d700  qeth      151552  drivers/s390/net/qeth.ko
  crash> sym qeth_send_ipa_cmd
  3ff802a9da8 (T) qeth_send_ipa_cmd [qeth] /root/linux/drivers/s390/net/qeth_core_main.c: 2944
  crash>

Now perf report displays the address of symbol qeth_send_ipa_cmd:
symbol__new:

  qeth_send_ipa_cmd 0x130f0-0x132ce

There is a difference of 0x68 between the entry in the symbol table (see
nm command above) and perf. The difference is from the offset the .text
segment of qeth.ko:

  [root@s8360047 perf]# readelf -a drivers/s390/net/qeth.ko
  Section Headers:
  [Nr] Name              Type             Address           Offset
       Size              EntSize          Flags  Link  Info  Align
  [ 0]                   NULL             0000000000000000  00000000
       0000000000000000  0000000000000000           0     0     0
  [ 1] .note.gnu.build-i NOTE             0000000000000000  00000040
       0000000000000024  0000000000000000   A       0     0     4
  [ 2] .text             PROGBITS         0000000000000000  00000068
       000000000001c8a0  0000000000000000  AX       0     0     8

As seen the .text segment has an offset of 0x68 with start address 0x0.
Therefore 0x68 is added to the address of qeth_send_ipa_cmd and thus
0x13088 + 0x68 = 0x130f0 is displayed.

This is wrong, perf report needs to display the start address of symbol
qeth_send_ipa_cmd at 0x13088 + qeth.ko.text section start address.

The qeth.ko module .text start address is available in the qeth.ko DSO
map. Just identify the kernel module symbols and correct the addresses.

With the fix I see this correct address for symbol: symbol__new:
qeth_send_ipa_cmd 0x3ff802a9da8-0x3ff802a9f86

Signed-off-by: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Hendrik Brueckner <brueckner@linux.vnet.ibm.com>
Cc: Thomas-Mich Richter <tmricht@linux.vnet.ibm.com>
Cc: Zvonko Kosic <zvonko.kosic@de.ibm.com>
LPU-Reference: 20170803134902.47207-1-tmricht@linux.vnet.ibm.com
Link: http://lkml.kernel.org/n/tip-q8lktlpoxb5e3dj52u1s1rw4@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
hifive-unleashed-5.1
Thomas Richter 2017-08-03 15:49:01 +02:00 committed by Arnaldo Carvalho de Melo
parent 9ad4652b66
commit 4a084ecfc8
3 changed files with 17 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
tools/perf/arch/s390/util/sym-handling.c
View File

@ -19,4 +19,11 @@ bool elf__needs_adjust_symbols(GElf_Ehdr ehdr)
return ehdr.e_type == ET_REL || ehdr.e_type == ET_DYN;
}
void arch__adjust_sym_map_offset(GElf_Sym *sym,
GElf_Shdr *shdr __maybe_unused,
struct map *map)
{
if (map->type == MAP__FUNCTION)
sym->st_value += map->start;
}
#endif

8
tools/perf/util/symbol-elf.c
View File

@ -793,6 +793,12 @@ static u64 ref_reloc(struct kmap *kmap)
void __weak arch__sym_update(struct symbol *s __maybe_unused,
GElf_Sym *sym __maybe_unused) { }
void __weak arch__adjust_sym_map_offset(GElf_Sym *sym, GElf_Shdr *shdr,
struct map *map __maybe_unused)
{
sym->st_value -= shdr->sh_addr - shdr->sh_offset;
}
int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss,
struct symsrc *runtime_ss, int kmodule)
{
@ -973,7 +979,7 @@ int dso__load_sym(struct dso *dso, struct map *map, struct symsrc *syms_ss,
/* Adjust symbol to map to file offset */
if (adjust_kernel_syms)
sym.st_value -= shdr.sh_addr - shdr.sh_offset;
arch__adjust_sym_map_offset(&sym, &shdr, map);
if (strcmp(section_name,
(curr_dso->short_name +

3
tools/perf/util/symbol.h
View File

@ -343,6 +343,9 @@ int setup_intlist(struct intlist **list, const char *list_str,
#ifdef HAVE_LIBELF_SUPPORT
bool elf__needs_adjust_symbols(GElf_Ehdr ehdr);
void arch__sym_update(struct symbol *s, GElf_Sym *sym);
void arch__adjust_sym_map_offset(GElf_Sym *sym,
GElf_Shdr *shdr __maybe_unused,
struct map *map __maybe_unused);
#endif
#define SYMBOL_A 0