queue-4.19/perf-record-fix-s390-missing-module-symbol-and-warni.patch

   1 From 6927a3d41c74f37e4350743d9b255a9b6d711a1b Mon Sep 17 00:00:00 2001
   2 From: Thomas Richter <tmricht@linux.ibm.com>
   3 Date: Wed, 22 May 2019 16:46:01 +0200
   4 Subject: perf record: Fix s390 missing module symbol and warning for non-root
   5  users
   6
   7 [ Upstream commit 6738028dd57df064b969d8392c943ef3b3ae705d ]
   8
   9 Command 'perf record' and 'perf report' on a system without kernel
  10 debuginfo packages uses /proc/kallsyms and /proc/modules to find
  11 addresses for kernel and module symbols. On x86 this works for root and
  12 non-root users.
  13
  14 On s390, when invoked as non-root user, many of the following warnings
  15 are shown and module symbols are missing:
  16
  17     proc/{kallsyms,modules} inconsistency while looking for
  18         "[sha1_s390]" module!
  19
  20 Command 'perf record' creates a list of module start addresses by
  21 parsing the output of /proc/modules and creates a PERF_RECORD_MMAP
  22 record for the kernel and each module. The following function call
  23 sequence is executed:
  24
  25   machine__create_kernel_maps
  26     machine__create_module
  27       modules__parse
  28         machine__create_module --> for each line in /proc/modules
  29           arch__fix_module_text_start
  30
  31 Function arch__fix_module_text_start() is s390 specific. It opens
  32 file /sys/module/<name>/sections/.text to extract the module's .text
  33 section start address. On s390 the module loader prepends a header
  34 before the first section, whereas on x86 the module's text section
  35 address is identical the the module's load address.
  36
  37 However module section files are root readable only. For non-root the
  38 read operation fails and machine__create_module() returns an error.
  39 Command perf record does not generate any PERF_RECORD_MMAP record
  40 for loaded modules. Later command perf report complains about missing
  41 module maps.
  42
  43 To fix this function arch__fix_module_text_start() always returns
  44 success. For root users there is no change, for non-root users
  45 the module's load address is used as module's text start address
  46 (the prepended header then counts as part of the text section).
  47
  48 This enable non-root users to use module symbols and avoid the
  49 warning when perf report is executed.
  50
  51 Output before:
  52
  53   [tmricht@m83lp54 perf]$ ./perf report -D | fgrep MMAP
  54   0 0x168 [0x50]: PERF_RECORD_MMAP ... x [kernel.kallsyms]_text
  55
  56 Output after:
  57
  58   [tmricht@m83lp54 perf]$ ./perf report -D | fgrep MMAP
  59   0 0x168 [0x50]: PERF_RECORD_MMAP ... x [kernel.kallsyms]_text
  60   0 0x1b8 [0x98]: PERF_RECORD_MMAP ... x /lib/modules/.../autofs4.ko.xz
  61   0 0x250 [0xa8]: PERF_RECORD_MMAP ... x /lib/modules/.../sha_common.ko.xz
  62   0 0x2f8 [0x98]: PERF_RECORD_MMAP ... x /lib/modules/.../des_generic.ko.xz
  63
  64 Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
  65 Reviewed-by: Hendrik Brueckner <brueckner@linux.ibm.com>
  66 Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
  67 Link: http://lkml.kernel.org/r/20190522144601.50763-4-tmricht@linux.ibm.com
  68 Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
  69 Signed-off-by: Sasha Levin <sashal@kernel.org>
  70 ---
  71  tools/perf/arch/s390/util/machine.c | 9 ++++++---
  72  1 file changed, 6 insertions(+), 3 deletions(-)
  73
  74 diff --git a/tools/perf/arch/s390/util/machine.c b/tools/perf/arch/s390/util/machine.c
  75 index 0b2054007314..a19690a17291 100644
  76 --- a/tools/perf/arch/s390/util/machine.c
  77 +++ b/tools/perf/arch/s390/util/machine.c
  78 @@ -5,16 +5,19 @@
  79  #include "util.h"
  80  #include "machine.h"
  81  #include "api/fs/fs.h"
  82 +#include "debug.h"
  83
  84  int arch__fix_module_text_start(u64 *start, const char *name)
  85  {
  86 +       u64 m_start = *start;
  87         char path[PATH_MAX];
  88
  89         snprintf(path, PATH_MAX, "module/%.*s/sections/.text",
  90                                 (int)strlen(name) - 2, name + 1);
  91 -
  92 -       if (sysfs__read_ull(path, (unsigned long long *)start) < 0)
  93 -               return -1;
  94 +       if (sysfs__read_ull(path, (unsigned long long *)start) < 0) {
  95 +               pr_debug2("Using module %s start:%#lx\n", path, m_start);
  96 +               *start = m_start;
  97 +       }
  98
  99         return 0;
 100  }
 101 --
 102 2.20.1
 103