linux.git/tools/lib/api, branch v7.2-rc1

tools lib api: Fix mount_overload() snprintf truncation and toupper range

2026-06-10T21:56:02+00:00

mount_overload() builds an environment variable name like
"PERF_SYSFS_ENVIRONMENT" from fs->name.  Two bugs:

1) snprintf() uses name_len as the buffer size instead of sizeof(upper_name).
   For fs->name = "sysfs" (len=5), the output is truncated to "PERF" (4
   chars + null), so getenv() never finds the intended variable.

2) mem_toupper() only uppercases name_len bytes, converting just the "PERF"
   prefix rather than the full string including the filesystem name portion.

Fix by using sizeof(upper_name) for snprintf and strlen(upper_name) for
mem_toupper, so the full "PERF_SYSFS_ENVIRONMENT" string is correctly
formatted and uppercased.

Reported-by: sashiko-bot 
Fixes: 73ca85ad364769ff ("tools lib api fs: Add FSTYPE__mount() method")
Cc: Jiri Olsa 
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo

tools lib api: Fix filename__write_int() writing uninitialized stack data

2026-06-10T21:56:01+00:00

filename__write_int() formats an integer into a 64-byte buffer with
sprintf() then passes sizeof(buf) (64) as the write length.  This
writes all 64 bytes including uninitialized stack data past the
formatted string.  Most sysfs files reject the oversized write,
making the function always return -1.

Fix by capturing the sprintf() return value and using it as the
write length.

Reported-by: sashiko-bot 
Fixes: 3b00ea938653d136 ("tools lib api fs: Add sysfs__write_int function")
Cc: Kan Liang 
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo

tools lib api: Fix missing null termination in filename__read_int/ull()

2026-06-10T21:56:01+00:00

filename__read_int() passes a stack buffer to read() using the full
sizeof(line) and then hands it to atoi() without null-terminating.
If a sysfs file fills the 64-byte buffer exactly, atoi() reads past
the array into uninitialized stack memory.

filename__read_ull_base() has the same issue with strtoull().

Fix both by reading sizeof(line) - 1 bytes and explicitly
null-terminating after a successful read.

Fixes: 3a351127cbc682c3 ("tools lib fs: Adopt filename__read_int from tools/perf/")
Reported-by: sashiko-bot 
Assisted-by: Claude:claude-opus-4.6
Signed-off-by: Arnaldo Carvalho de Melo

libapi: Add missing header with NAME_MAX define to io_dir.h

2025-03-13T07:29:36+00:00

Most systems get this indirectly, but some odd cases (some musl libc
systems) can't find it, so just add the header where NAME_MAX is defined
to avoid that.

Fixes: d118b08f7eee6d6f ("tools lib api: Add io_dir an allocation free readdir alternative")
Signed-off-by: Arnaldo Carvalho de Melo 
Link: https://lore.kernel.org/r/20250310194534.265487-2-acme@kernel.org
Signed-off-by: Namhyung Kim

tools lib api: Add io_dir an allocation free readdir alternative

2025-02-24T23:46:33+00:00

glibc's opendir allocates a minimum of 32kb, when called recursively
for a directory tree the memory consumption can add up - nearly 300kb
during perf start-up when processing modules. Add a stack allocated
variant of readdir sized a little more than 1kb.

As getdents64 may be missing from libc, add support using syscall. As
the system call number maybe missing, add #defines for those.

Note, an earlier version of this patch had a feature test for
getdents64 but there were problems on certains distros where
getdents64 would be #define renamed to getdents breaking the code. The
syscall use was made uncondtional to work around this. There is
context in:
https://lore.kernel.org/lkml/20231207050433.1426834-1-irogers@google.com/

Signed-off-by: Ian Rogers 
Link: https://lore.kernel.org/r/20250222061015.303622-2-irogers@google.com
Signed-off-by: Namhyung Kim

tool api fs: Correctly encode errno for read/write open failures

2024-12-09T20:52:42+00:00

Switch from returning -1 to -errno so that callers can determine types
of failure.

Reviewed-by: Namhyung Kim 
Signed-off-by: Ian Rogers 
Acked-by: Arnaldo Carvalho de Melo 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Andi Kleen 
Cc: Athira Rajeev 
Cc: Ben Gainey 
Cc: Colin Ian King 
Cc: Dominique Martinet 
Cc: Ilkka Koskinen 
Cc: Ingo Molnar 
Cc: James Clark 
Cc: Jiri Olsa 
Cc: Kan Liang 
Cc: Mark Rutland 
Cc: Oliver Upton 
Cc: Paran Lee 
Cc: Peter Zijlstra 
Cc: Steinar H. Gunderson 
Cc: Steven Rostedt (VMware) 
Cc: Thomas Falcon 
Cc: Weilin Wang 
Cc: Yang Jihong 
Cc: Yang Li 
Cc: Ze Gao 
Cc: Zixian Cai 
Cc: zhaimingbing 
Link: https://lore.kernel.org/r/20241118225345.889810-3-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo

tools api io: Ensure line_len_out is always initialized

2024-11-09T06:46:44+00:00

Ensure initialization to avoid compiler warnings about potential use
of uninitialized variables.

Signed-off-by: Ian Rogers 
Cc: Ravi Bangoria 
Cc: Yoshihiro Furudera 
Cc: Howard Chu 
Cc: Ze Gao 
Cc: Changbin Du 
Cc: Junhao He 
Cc: Weilin Wang 
Cc: James Clark 
Cc: Oliver Upton 
Cc: Athira Jajeev 
Link: https://lore.kernel.org/r/20241109003759.473460-2-irogers@google.com
Signed-off-by: Namhyung Kim

tools: Drop nonsensical -O6

2024-09-11T16:08:36+00:00

-O6 is very much not-a-thing. Really, this should've been dropped
entirely in 49b3cd306e60b9d8 ("tools: Set the maximum optimization level
according to the compiler being used") instead of just passing it for
not-Clang.

Just collapse it down to -O3, instead of "-O6 unless Clang, in which case
-O3".

GCC interprets > -O3 as -O3. It doesn't even interpret > -O3 as -Ofast,
which is a good thing, given -Ofast has specific (non-)requirements for
code built using it. So, this does nothing except look a bit daft.

Remove the silliness and also save a few lines in the Makefiles accordingly.

Reviewed-by: Ian Rogers 
Reviewed-by: Jesper Juhl 
Signed-off-by: Sam James 
Acked-by: Namhyung Kim 
Cc: Adrian Hunter 
Cc: Alexander Shishkin 
Cc: Bill Wendling 
Cc: Ingo Molnar 
Cc: Jiri Olsa 
Cc: Justin Stitt 
Cc: Kan Liang 
Cc: Mark Rutland 
Cc: Nathan Chancellor 
Cc: Nick Desaulniers 
Cc: Peter Zijlstra 
Cc: llvm@lists.linux.dev
Link: https://lore.kernel.org/r/4f01524fa4ea91c7146a41e26ceaf9dae4c127e4.1725821201.git.sam@gentoo.org
Signed-off-by: Arnaldo Carvalho de Melo

perf list: Give clues if failed to open tracing events directory

2024-08-01T15:11:33+00:00

When executing the command "perf list", I met "Error: failed to open
tracing events directory" twice, the first reason is that there is no
"/sys/kernel/tracing/events" directory due to it does not enable the
kernel tracing infrastructure with CONFIG_FTRACE, the second reason
is that there is no root privileges.

Add the error string to tell the users what happened and what should
to do, and also call put_tracing_file() to free events_path a little
later to avoid messy code in the error message.

At the same time, just remove the redundant "/" of the file path in
the function get_tracing_file(), otherwise it shows something like
"/sys/kernel/tracing//events".

Before:

  $ ./perf list
  Error: failed to open tracing events directory

After:

(1) Without CONFIG_FTRACE

  $ ./perf list
  Error: failed to open tracing events directory
  /sys/kernel/tracing/events: No such file or directory

(2) With CONFIG_FTRACE but no root privileges

  $ ./perf list
  Error: failed to open tracing events directory
  /sys/kernel/tracing/events: Permission denied

Committer testing:

Redirect stdout to null to quickly test the patch:

Before:

  $ perf list > /dev/null
  Error: failed to open tracing events directory
  $

After:

  $ perf list > /dev/null
  Error: failed to open tracing events directory
  /sys/kernel/tracing/events: Permission denied
  $

Signed-off-by: Tiezhu Yang 
Tested-by: Arnaldo Carvalho de Melo 
Cc: Ingo Molnar 
Cc: Namhyung Kim 
Cc: Peter Zijlstra 
Link: https://lore.kernel.org/lkml/20240730062301.23244-3-yangtiezhu@loongson.cn
Signed-off-by: Arnaldo Carvalho de Melo

tools api io: Move filling the io buffer to its own function

2024-05-30T17:05:34+00:00

In general a read fills 4kb so filling the buffer is a 1 in 4096
operation, move it out of the io__get_char function to avoid some
checking overhead and to better hint the function is good to inline.

For perf's IO intensive internal (non-rigorous) benchmarks there's a
small improvement to kallsyms-parsing with a default build.

Before:
```
$ perf bench internals all
Computing performance of single threaded perf event synthesis by
synthesizing events on the perf process itself:
  Average synthesis took: 146.322 usec (+- 0.305 usec)
  Average num. events: 61.000 (+- 0.000)
  Average time per event 2.399 usec
  Average data synthesis took: 145.056 usec (+- 0.155 usec)
  Average num. events: 329.000 (+- 0.000)
  Average time per event 0.441 usec

  Average kallsyms__parse took: 162.313 ms (+- 0.599 ms)
...
Computing performance of sysfs PMU event scan for 100 times
  Average core PMU scanning took: 53.720 usec (+- 7.823 usec)
  Average PMU scanning took: 375.145 usec (+- 23.974 usec)
```
After:
```
$ perf bench internals all
Computing performance of single threaded perf event synthesis by
synthesizing events on the perf process itself:
  Average synthesis took: 127.829 usec (+- 0.079 usec)
  Average num. events: 61.000 (+- 0.000)
  Average time per event 2.096 usec
  Average data synthesis took: 133.652 usec (+- 0.101 usec)
  Average num. events: 327.000 (+- 0.000)
  Average time per event 0.409 usec

  Average kallsyms__parse took: 150.415 ms (+- 0.313 ms)
...
Computing performance of sysfs PMU event scan for 100 times
  Average core PMU scanning took: 47.790 usec (+- 1.178 usec)
  Average PMU scanning took: 376.945 usec (+- 23.683 usec)
```

Signed-off-by: Ian Rogers 
Signed-off-by: Namhyung Kim 
Link: https://lore.kernel.org/r/20240519181716.4088459-1-irogers@google.com