kernel/tools/perf/util/unwind-libunwind-local.c, branch linux-6.2.y

perf unwind: Fix unitialized 'offset' variable on aarch64

2022-07-02T12:16:52Z

Commit dc2cf4ca866f5715 ("perf unwind: Fix segbase for ld.lld linked objects") uncovered the following issue on aarch64: util/unwind-libunwind-local.c: In function 'find_proc_info': util/unwind-libunwind-local.c:386:28: error: 'offset' may be used uninitialized in this function [-Werror=maybe-uninitialized] 386 | if (ofs > 0) { | ^ util/unwind-libunwind-local.c:199:22: note: 'offset' was declared here 199 | u64 address, offset; | ^~~~~~ util/unwind-libunwind-local.c:371:20: error: 'offset' may be used uninitialized in this function [-Werror=maybe-uninitialized] 371 | if (ofs <= 0) { | ^ util/unwind-libunwind-local.c:199:22: note: 'offset' was declared here 199 | u64 address, offset; | ^~~~~~ util/unwind-libunwind-local.c:363:20: error: 'offset' may be used uninitialized in this function [-Werror=maybe-uninitialized] 363 | if (ofs <= 0) { | ^ util/unwind-libunwind-local.c:199:22: note: 'offset' was declared here 199 | u64 address, offset; | ^~~~~~ In file included from util/libunwind/arm64.c:37: Fixes: dc2cf4ca866f5715 ("perf unwind: Fix segbase for ld.lld linked objects") Signed-off-by: Ivan Babrou Cc: Alexander Shishkin Cc: Fangrui Song Cc: Ian Rogers Cc: James Clark Cc: Jiri Olsa Cc: kernel-team@cloudflare.com Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/20220701182046.12589-1-ivan@cloudflare.com Signed-off-by: Arnaldo Carvalho de Melo

perf unwind: Fix uninitialized variable

2022-06-19T13:41:43Z

The 'ret' variable may be uninitialized on error goto paths. Fixes: dc2cf4ca866f5715 ("perf unwind: Fix segbase for ld.lld linked objects") Reported-by: Sedat Dilek Reviewed-by: Fangrui Song Signed-off-by: Ian Rogers Tested-by: Sedat Dilek # LLVM-14 (x86-64) Cc: Fangrui Song Cc: Ingo Molnar Cc: llvm@lists.linux.dev Cc: Peter Zijlstra Cc: Sebastian Ullrich Link: https://lore.kernel.org/r/20220607000851.39798-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo

perf unwind: Fix segbase for ld.lld linked objects

2022-06-03T19:20:25Z

segbase is the address of .eh_frame_hdr and table_data is segbase plus the header size. find_proc_info computes segbase as `map->start + segbase - map->pgoff` which is wrong when * .eh_frame_hdr and .text are in different PT_LOAD program headers * and their p_vaddr difference does not equal their p_offset difference Since 10.0, ld.lld's default --rosegment -z noseparate-code layout has such R and RX PT_LOAD program headers. ld.lld (default) => perf report fails to unwind `perf record --call-graph dwarf` recorded data ld.lld --no-rosegment => ok (trivial, no R PT_LOAD) ld.lld -z separate-code => ok but by luck: there are two PT_LOAD but their p_vaddr difference equals p_offset difference ld.bfd -z noseparate-code => ok (trivial, no R PT_LOAD) ld.bfd -z separate-code (default for Linux/x86) => ok but by luck: there are two PT_LOAD but their p_vaddr difference equals p_offset difference To fix the issue, compute segbase as dso's base address plus PT_GNU_EH_FRAME's p_vaddr. The base address is computed by iterating over all dso-associated maps and then subtract the first PT_LOAD p_vaddr (the minimum guaranteed by generic ABI) from the minimum address. In libunwind, find_proc_info transitively called by unw_step is cached, so the iteration overhead is acceptable. Reported-by: Sebastian Ullrich Reviewed-by: Ian Rogers Signed-off-by: Fangrui Song Cc: Ingo Molnar Cc: Peter Zijlstra Cc: llvm@lists.linux.dev Link: https://github.com/ClangBuiltLinux/linux/issues/1646 Link: https://lore.kernel.org/r/20220527182039.673248-1-maskray@google.com Signed-off-by: Arnaldo Carvalho de Melo

perf unwind: Don't show unwind error messages when augmenting frame pointer stack

2022-04-09T15:34:29Z

Commit Fixes: b9f6fbb3b2c29736 ("perf arm64: Inject missing frames when using 'perf record --call-graph=fp'") intended to add a 'best effort' DWARF unwind that improved the frame pointer stack in most scenarios. It's expected that the unwind will fail sometimes, but this shouldn't be reported as an error. It only works when the return address can be determined from the contents of the link register alone. Fix the error shown when the unwinder requires extra registers by adding a new flag that suppresses error messages. This flag is not set in the normal --call-graph=dwarf unwind mode so that behavior is not changed. Fixes: b9f6fbb3b2c29736 ("perf arm64: Inject missing frames when using 'perf record --call-graph=fp'") Reported-by: John Garry Signed-off-by: James Clark Tested-by: John Garry Cc: Alexander Shishkin Cc: Alexandre Truong Cc: German Gomez Cc: Jiri Olsa Cc: Mark Rutland Cc: Namhyung Kim Link: https://lore.kernel.org/r/20220406145651.1392529-1-james.clark@arm.com Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Fix various typos in comments

2021-03-23T20:13:43Z

Fix ~124 single-word typos and a few spelling errors in the perf tooling code, accumulated over the years. Signed-off-by: Ingo Molnar Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20210321113734.GA248990@gmail.com Link: http://lore.kernel.org/lkml/20210323160915.GA61903@gmail.com Signed-off-by: Arnaldo Carvalho de Melo

perf tools: Replace zero-length array with flexible-array

2020-05-28T13:03:27Z

The current codebase makes use of the zero-length array language extension to the C90 standard, but the preferred mechanism to declare variable-length types such as these ones is a flexible array member[1][2], introduced in C99: struct foo { int stuff; struct boo array[]; }; By making use of the mechanism above, we will get a compiler warning in case the flexible array does not occur last in the structure, which will help us prevent some kind of undefined behavior bugs from being inadvertently introduced[3] to the codebase from now on. Also, notice that, dynamic memory allocations won't be affected by this change: "Flexible array members have incomplete type, and so the sizeof operator may not be applied. As a quirk of the original implementation of zero-length arrays, sizeof evaluates to zero."[1] sizeof(flexible-array-member) triggers a warning because flexible array members have incomplete type[1]. There are some instances of code in which the sizeof operator is being incorrectly/erroneously applied to zero-length arrays and the result is zero. Such instances may be hiding some bugs. So, this work (flexible-array member conversions) will also help to get completely rid of those sorts of issues. This issue was found with the help of Coccinelle. [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html [2] https://github.com/KSPP/linux/issues/21 [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") Signed-off-by: Gustavo A. R. Silva Cc: Adrian Hunter Cc: Alexander Shishkin Cc: Gustavo A. R. Silva Cc: Ian Rogers Cc: Jiri Olsa Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/20200515172926.GA31976@embeddedor Signed-off-by: Arnaldo Carvalho de Melo

perf maps: Rename 'mg' variables to 'maps'

2019-11-26T14:07:46Z

Continuing the merge of 'struct maps' with 'struct map_groups'. Cc: Adrian Hunter Cc: Andi Kleen Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lkml.kernel.org/n/tip-z8d14wrw393a0fbvmnk1bqd9@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf map_symbol: Rename ms->mg to ms->maps

2019-11-26T14:07:46Z

One more step on the merge of 'struct maps' with 'struct map_groups'. Cc: Adrian Hunter Cc: Andi Kleen Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lkml.kernel.org/n/tip-61rra2wg392rhvdgw421wzpt@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf addr_location: Rename al->mg to al->maps

2019-11-26T14:07:46Z

One more step on the merge of 'struct maps' with 'struct map_groups'. Cc: Adrian Hunter Cc: Andi Kleen Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lkml.kernel.org/n/tip-foo95pyyp3bhocbt7yd8qrvq@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf thread: Rename thread->mg to thread->maps

2019-11-26T14:07:46Z

One more step on the merge of 'struct maps' with 'struct map_groups'. Cc: Adrian Hunter Cc: Andi Kleen Cc: Jiri Olsa Cc: Namhyung Kim Link: https://lkml.kernel.org/n/tip-69vcr8pubpym90skxhmbwhiw@git.kernel.org Signed-off-by: Arnaldo Carvalho de Melo