kernel/linux.git/tools/perf/util, branch v5.19

perf bpf: Remove undefined behavior from bpf_perf_object__next()

2022-07-27T14:19:39+00:00

bpf_perf_object__next() folded the last element in the list test with the empty list test. However, this meant that offsets were computed against null and that a struct list_head was compared against a 'struct bpf_perf_object'. Working around this with clang's undefined behavior sanitizer required -fno-sanitize=null and -fno-sanitize=object-size. Remove the undefined behavior by using the regular Linux list APIs and handling the starting case separately from the end testing case. Looking at uses like bpf_perf_object__for_each(), as the constant NULL or non-NULL argument can be constant propagated, the code is no less efficient. Signed-off-by: Ian Rogers Cc: Alexander Shishkin Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Christy Lee Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mark Rutland Cc: Miaoqian Lin Cc: Namhyung Kim Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Tom Rix Cc: bpf@vger.kernel.org Cc: llvm@lists.linux.dev Link: https://lore.kernel.org/r/20220726220921.2567761-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo

perf symbol: Skip symbols if SHF_ALLOC flag is not set

2022-07-27T14:17:50+00:00

Some symbols are observed with the 'st_value' field zeroed. E.g. libc.so.6 in Ubuntu contains a symbol '__evoke_link_warning_getwd' which resides in the '.gnu.warning.getwd' section. Unlike normal sections, such kind of sections are used for linker warning when a file calls deprecated functions, but they are not part of memory images, the symbols in these sections should be dropped. This patch checks the section attribute SHF_ALLOC bit, if the bit is not set, it skips symbols to avoid spurious ones. Suggested-by: Fangrui Song Signed-off-by: Leo Yan Acked-by: Namhyung Kim Cc: Alexander Shishkin Cc: Chang Rui Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mark Rutland Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20220724060013.171050-3-leo.yan@linaro.org Signed-off-by: Arnaldo Carvalho de Melo

perf symbol: Correct address for bss symbols

2022-07-27T14:17:50+00:00

When using 'perf mem' and 'perf c2c', an issue is observed that tool reports the wrong offset for global data symbols. This is a common issue on both x86 and Arm64 platforms. Let's see an example, for a test program, below is the disassembly for its .bss section which is dumped with objdump: ... Disassembly of section .bss: 0000000000004040 : ... 0000000000004080 : ... 00000000000040c0 : ... 0000000000004100 : ... First we used 'perf mem record' to run the test program and then used 'perf --debug verbose=4 mem report' to observe what's the symbol info for 'buf1' and 'buf2' structures. # ./perf mem record -e ldlat-loads,ldlat-stores -- false_sharing.exe 8 # ./perf --debug verbose=4 mem report ... dso__load_sym_internal: adjusting symbol: st_value: 0x40c0 sh_addr: 0x4040 sh_offset: 0x3028 symbol__new: buf2 0x30a8-0x30e8 ... dso__load_sym_internal: adjusting symbol: st_value: 0x4080 sh_addr: 0x4040 sh_offset: 0x3028 symbol__new: buf1 0x3068-0x30a8 ... The perf tool relies on libelf to parse symbols, in executable and shared object files, 'st_value' holds a virtual address; 'sh_addr' is the address at which section's first byte should reside in memory, and 'sh_offset' is the byte offset from the beginning of the file to the first byte in the section. The perf tool uses below formula to convert a symbol's memory address to a file address: file_address = st_value - sh_addr + sh_offset ^ ` Memory address We can see the final adjusted address ranges for buf1 and buf2 are [0x30a8-0x30e8) and [0x3068-0x30a8) respectively, apparently this is incorrect, in the code, the structure for 'buf1' and 'buf2' specifies compiler attribute with 64-byte alignment. The problem happens for 'sh_offset', libelf returns it as 0x3028 which is not 64-byte aligned, combining with disassembly, it's likely libelf doesn't respect the alignment for .bss section, therefore, it doesn't return the aligned value for 'sh_offset'. Suggested by Fangrui Song, ELF file contains program header which contains PT_LOAD segments, the fields p_vaddr and p_offset in PT_LOAD segments contain the execution info. A better choice for converting memory address to file address is using the formula: file_address = st_value - p_vaddr + p_offset This patch introduces elf_read_program_header() which returns the program header based on the passed 'st_value', then it uses the formula above to calculate the symbol file address; and the debugging log is updated respectively. After applying the change: # ./perf --debug verbose=4 mem report ... dso__load_sym_internal: adjusting symbol: st_value: 0x40c0 p_vaddr: 0x3d28 p_offset: 0x2d28 symbol__new: buf2 0x30c0-0x3100 ... dso__load_sym_internal: adjusting symbol: st_value: 0x4080 p_vaddr: 0x3d28 p_offset: 0x2d28 symbol__new: buf1 0x3080-0x30c0 ... Fixes: f17e04afaff84b5c ("perf report: Fix ELF symbol parsing") Reported-by: Chang Rui Suggested-by: Fangrui Song Signed-off-by: Leo Yan Acked-by: Namhyung Kim Cc: Alexander Shishkin Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mark Rutland Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20220724060013.171050-2-leo.yan@linaro.org Signed-off-by: Arnaldo Carvalho de Melo

perf synthetic-events: Ignore dead threads during event synthesis

2022-07-02T12:22:26+00:00

When it synthesize various task events, it scans the list of task first and then accesses later. There's a window threads can die between the two and proc entries may not be available. Instead of bailing out, we can ignore that thread and move on. Signed-off-by: Namhyung Kim Acked-by: Ian Rogers Cc: Jiri Olsa Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/20220701205458.985106-2-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf synthetic-events: Don't sort the task scan result from /proc

2022-07-02T12:21:41+00:00

It should not sort the result as procfs already returns a proper ordering of tasks. Actually sorting the order caused problems that it doesn't guararantee to process the main thread first. Signed-off-by: Namhyung Kim Acked-by: Ian Rogers Cc: Jiri Olsa Cc: Peter Zijlstra Link: http://lore.kernel.org/lkml/20220701205458.985106-1-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf unwind: Fix unitialized 'offset' variable on aarch64

2022-07-02T12:16:52+00:00

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 bpf: 8 byte align bpil data

2022-06-28T15:05:25+00:00

bpil data is accessed assuming 64-bit alignment resulting in undefined behavior as the data is just byte aligned. With an -fsanitize=undefined build the following errors are observed: $ sudo perf record -a sleep 1 util/bpf-event.c:310:22: runtime error: load of misaligned address 0x55f61084520f for type '__u64', which requires 8 byte alignment 0x55f61084520f: note: pointer points here a8 fe ff ff 3c 51 d3 c0 ff ff ff ff 04 84 d3 c0 ff ff ff ff d8 aa d3 c0 ff ff ff ff a4 c0 d3 c0 ^ util/bpf-event.c:311:20: runtime error: load of misaligned address 0x55f61084522f for type '__u32', which requires 4 byte alignment 0x55f61084522f: note: pointer points here ff ff ff ff c7 17 00 00 f1 02 00 00 1f 04 00 00 58 04 00 00 00 00 00 00 0f 00 00 00 63 02 00 00 ^ util/bpf-event.c:198:33: runtime error: member access within misaligned address 0x55f61084523f for type 'const struct bpf_func_info', which requires 4 byte alignment 0x55f61084523f: note: pointer points here 58 04 00 00 00 00 00 00 0f 00 00 00 63 02 00 00 3b 00 00 00 ab 02 00 00 44 00 00 00 14 03 00 00 Correct this by rouding up the data sizes and aligning the pointers. Signed-off-by: Ian Rogers Acked-by: Andrii Nakryiko Cc: Alexander Shishkin Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Dave Marchevsky Cc: Ingo Molnar Cc: Jiri Olsa Cc: John Fastabend Cc: KP Singh Cc: Mark Rutland Cc: Martin KaFai Lau Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Quentin Monnet Cc: Song Liu Cc: Stephane Eranian Cc: Yonghong Song Cc: bpf@vger.kernel.org Cc: netdev@vger.kernel.org Link: https://lore.kernel.org/r/20220614014714.1407239-1-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo

perf offcpu: Accept allowed sample types only

2022-06-28T14:45:45+00:00

As offcpu-time event is synthesized at the end, it could not get the all the sample info. Define OFFCPU_SAMPLE_TYPES for allowed ones and mask out others in evsel__config() to prevent parse errors. Because perf sample parsing assumes a specific ordering with the sample types, setting unsupported one would make it fail to read data like perf record -d/--data. Fixes: edc41a1099c2d08c ("perf record: Enable off-cpu analysis with BPF") Signed-off-by: Namhyung Kim Cc: Blake Jones Cc: Hao Luo Cc: Ian Rogers Cc: Jiri Olsa Cc: Milian Wolff Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Song Liu Cc: bpf@vger.kernel.org Link: http://lore.kernel.org/lkml/20220624231313.367909-3-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf offcpu: Fix build failure on old kernels

2022-06-28T14:41:26+00:00

Old kernels have a 'struct task_struct' which contains a "state" field and newer kernels have "__state" instead. While the get_task_state() in the BPF code handles that in some way, it assumed the current kernel has the new definition and it caused a build error on old kernels. We should not assume anything and access them carefully. Do not use 'task struct' directly access it instead using new and old definitions in a row. Fixes: edc41a1099c2d08c ("perf record: Enable off-cpu analysis with BPF") Reported-by: Ian Rogers Signed-off-by: Namhyung Kim Cc: Blake Jones Cc: Hao Luo Cc: Jiri Olsa Cc: Milian Wolff Cc: Peter Zijlstra Cc: Song Liu Cc: bpf@vger.kernel.org Link: http://lore.kernel.org/lkml/20220624231313.367909-2-namhyung@kernel.org Signed-off-by: Arnaldo Carvalho de Melo

perf inject: Adjust output data offset for backward compatibility

2022-06-26T15:32:55+00:00

When 'perf inject' creates a new file, it reuses the data offset from the input file. If there has been a change on the size of the header, as happened in v5.12 -> v5.13, the new offsets will be wrong, resulting in a corrupted output file. This change adds the function perf_session__data_offset to compute the data offset based on the current header size, and uses that instead of the offset from the original input file. Signed-off-by: Raul Silvera Acked-by: Adrian Hunter Cc: Alexander Shishkin Cc: Athira Jajeev Cc: Colin Ian King Cc: Dave Marchevsky Cc: Ian Rogers Cc: Ingo Molnar Cc: Jiri Olsa Cc: Mark Rutland Cc: Namhyung Kim Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20220621152725.2668041-1-rsilvera@google.com Signed-off-by: Arnaldo Carvalho de Melo