kernel/linux.git/tools/lib/api/fs/fs.c, branch v6.6.131

tools api fs: More thread safety for global filesystem variables

2023-06-14T02:40:32+00:00

Multiple threads, such as with "perf top", may race to initialize a file system path like hugetlbfs. The racy initialization of the path leads to at least memory leaks. To avoid this initialize each fs for reading the mount point path with pthread_once. Mounting the file system may also be racy, so introduce a mutex over the function. This does mean that the path is being accessed with and without a mutex, which is inherently racy but hopefully benign, especially as there are fewer callers to fs__mount. Remove the fs__entries by directly using global variables, this was done as no argument like the index can be passed to the init once routine. Issue found and tested with "perf top" and address sanitizer. Signed-off-by: Ian Rogers Cc: Adrian Hunter Cc: Jiri Olsa Cc: Namhyung Kim Cc: bpf@vger.kernel.org Link: https://lore.kernel.org/r/20230609224004.180988-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Avoid large static PATH_MAX arrays

2023-05-28T13:22:40+00:00

Change struct fs to have a pointer to a dynamically allocated array rather than an array. This reduces the size of fs__entries from 24,768 bytes to 240 bytes. Read paths into a stack allocated array and strdup. Fix off-by-1 fscanf %s in fs__read_mounts caught by address sanitizer. Signed-off-by: Ian Rogers Link: https://lore.kernel.org/r/20230526183401.2326121-7-irogers@google.com Cc: K Prateek Nayak Cc: Ravi Bangoria Cc: Mark Rutland Cc: Ross Zwisler Cc: Steven Rostedt (Google) Cc: Sean Christopherson Cc: Yang Jihong Cc: Peter Zijlstra Cc: Adrian Hunter Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Masami Hiramatsu (Google) Cc: Namhyung Kim Cc: Leo Yan Cc: Andi Kleen Cc: Alexander Shishkin Cc: Kan Liang Cc: Tiezhu Yang Cc: Ingo Molnar Cc: Paolo Bonzini Cc: linux-kernel@vger.kernel.org Cc: linux-perf-users@vger.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools api fs: Make xxx__mountpoint() more scalable

2020-04-16T15:19:12+00:00

The xxx_mountpoint() interface provided by fs.c finds mount points for common pseudo filesystems. The first time xxx_mountpoint() is invoked, it scans the mount table (/proc/mounts) looking for a match. If found, it is cached. The price to scan /proc/mounts is paid once if the mount is found. When the mount point is not found, subsequent calls to xxx_mountpoint() scan /proc/mounts over and over again. There is no caching. This causes a scaling issue in perf record with hugeltbfs__mountpoint(). The function is called for each process found in synthesize__mmap_events(). If the machine has thousands of processes and if the /proc/mounts has many entries this could cause major overhead in perf record. We have observed multi-second slowdowns on some configurations. As an example on a laptop: Before: $ sudo umount /dev/hugepages $ strace -e trace=openat -o /tmp/tt perf record -a ls $ fgrep mounts /tmp/tt 285 After: $ sudo umount /dev/hugepages $ strace -e trace=openat -o /tmp/tt perf record -a ls $ fgrep mounts /tmp/tt 1 One could argue that the non-caching in case the moint point is not found is intentional. That way subsequent calls may discover a moint point if the sysadmin mounts the filesystem. But the same argument could be made against caching the mount point. It could be unmounted causing errors. It all depends on the intent of the interface. This patch assumes it is expected to scan /proc/mounts once. The patch documents the caching behavior in the fs.h header file. An alternative would be to just fix perf record. But it would solve the problem with hugetlbs__mountpoint() but there could be similar issues (possibly down the line) with other xxx_mountpoint() calls in perf or other tools. Signed-off-by: Stephane Eranian Reviewed-by: Ian Rogers Acked-by: Jiri Olsa Cc: Alexander Shishkin Cc: Andrey Zhizhikin Cc: Kan Liang Cc: Kefeng Wang Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Petr Mladek Cc: Thomas Gleixner Link: http://lore.kernel.org/lkml/20200402154357.107873-3-irogers@google.com Signed-off-by: Ian Rogers Signed-off-by: Arnaldo Carvalho de Melo

tools lib api fs: Fix gcc9 stringop-truncation compilation error

2020-01-06T14:46:09+00:00

GCC9 introduced string hardening mechanisms, which exhibits the error during fs api compilation: error: '__builtin_strncpy' specified bound 4096 equals destination size [-Werror=stringop-truncation] This comes when the length of copy passed to strncpy is is equal to destination size, which could potentially lead to buffer overflow. There is a need to mitigate this potential issue by limiting the size of destination by 1 and explicitly terminate the destination with NULL. Signed-off-by: Andrey Zhizhikin Reviewed-by: Petr Mladek Acked-by: Jiri Olsa Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Daniel Borkmann Cc: Kefeng Wang Cc: Martin KaFai Lau Cc: Petr Mladek Cc: Sergey Senozhatsky Cc: Song Liu Cc: Yonghong Song Cc: bpf@vger.kernel.org Cc: netdev@vger.kernel.org Link: http://lore.kernel.org/lkml/20191211080109.18765-1-andrey.zhizhikin@leica-geosystems.com Signed-off-by: Arnaldo Carvalho de Melo

tools lib api: Renaming pr_warning to pr_warn

2019-10-18T13:02:57+00:00

For kernel logging macro, pr_warning is completely removed and replaced by pr_warn, using pr_warn in tools lib api for symmetry to kernel logging macro, then we could drop pr_warning in the whole linux code. Changing __pr_warning to __pr_warn to be consistent. Link: http://lkml.kernel.org/r/20191018031850.48498-30-wangkefeng.wang@huawei.com To: linux-kernel@vger.kernel.org Cc: Arnaldo Carvalho de Melo Signed-off-by: Kefeng Wang Reviewed-by: Sergey Senozhatsky Signed-off-by: Petr Mladek

docs: Fix some broken references

2018-06-15T21:10:01+00:00

As we move stuff around, some doc references are broken. Fix some of them via this script: ./scripts/documentation-file-ref-check --fix Manually checked if the produced result is valid, removing a few false-positives. Acked-by: Takashi Iwai Acked-by: Masami Hiramatsu Acked-by: Stephen Boyd Acked-by: Charles Keepax Acked-by: Mathieu Poirier Reviewed-by: Coly Li Signed-off-by: Mauro Carvalho Chehab Acked-by: Jonathan Corbet

tools lib api fs: Add sysfs__read_xll function

2018-02-16T13:09:23+00:00

Adding sysfs__read_xll function to be able to read sysfs files with hex numbers in, which do not have 0x prefix. Signed-off-by: Jiri Olsa Cc: Alexander Shishkin Cc: David Ahern Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20180206181813.10943-6-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

tools lib api fs: Add filename__read_xll function

2018-02-16T13:09:23+00:00

Adding filename__read_xll function to be able to read files with hex numbers in, which do not have 0x prefix. Signed-off-by: Jiri Olsa Cc: Alexander Shishkin Cc: David Ahern Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lkml.kernel.org/r/20180206181813.10943-5-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

License cleanup: add SPDX GPL-2.0 license identifier to files with no license

2017-11-02T10:10:55+00:00

Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart Reviewed-by: Philippe Ombredanne Reviewed-by: Thomas Gleixner Signed-off-by: Greg Kroah-Hartman

tools lib api fs: Add sysfs__write_int function

2017-06-21T14:35:27+00:00

Add sysfs__write_int() to ease up writing int to sysfs. New interface is: int sysfs__write_int(const char *entry, int value); Also, introducing filename__write_int() which is useful for new helpers to write sysctl values. Signed-off-by: Kan Liang Acked-by: Jiri Olsa Cc: Andi Kleen Cc: Kan Liang Cc: Peter Zijlstra Cc: Robert Elliott Cc: Stephane Eranian Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/1495825538-5230-2-git-send-email-kan.liang@intel.com Signed-off-by: Arnaldo Carvalho de Melo