linux/tools/perf/util/arm64-frame-pointer-unwind-support.h

/* SPDX-License-Identifier: GPL-2.0 */
#ifndef __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H
#define __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H

#include "event.h"
#include "thread.h"

u64 get_leaf_frame_caller_aarch64(struct perf_sample *sample, struct thread *thread, int user_idx);

#endif /* __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H */
perf arm64: Inject missing frames when using 'perf record --call-graph=fp' When unwinding using frame pointers on ARM64, the return address of the current function may not have been pushed into the stack when a function was interrupted, which makes perf show an incorrect call graph to the user. Consider the following example program: void leaf() { /* long computation / } void parent() { // (1) leaf(); // (2) } ... could be compiled into (using gcc -fno-inline -fno-omit-frame-pointer): leaf: / long computation */ nop ret parent: // (1) stp x29, x30, [sp, -16]! mov x29, sp bl parent nop ldp x29, x30, [sp], 16 // (2) ret If the program is interrupted at (1), (2), or any point in "leaf:", the call graph will skip the callers of the current function. We can unwind using the dwarf info and check if the return addr is the same as the LR register, and inject the missing frame into the call graph. Before this patch, the above example shows the following call-graph when recording using "--call-graph fp" mode in ARM64: # Children Self Command Shared Object Symbol # ........ ........ ........ ................ ...................... # 99.86% 99.86% program3 program3 [.] leaf \| ---_start __libc_start_main main leaf As can be seen, the "parent" function is missing. This is specially problematic in "leaf" because for leaf functions the compiler may always omit pushing the return addr into the stack. After this patch, it shows the correct graph: # Children Self Command Shared Object Symbol # ........ ........ ........ ................ ...................... # 99.86% 99.86% program3 program3 [.] leaf \| ---_start __libc_start_main main parent leaf Reviewed-by: James Clark <james.clark@arm.com> Signed-off-by: Alexandre Truong <alexandre.truong@arm.com> Acked-by: Jiri Olsa <jolsa@kernel.org> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: John Garry <john.garry@huawei.com> Cc: Leo Yan <leo.yan@linaro.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mathieu Poirier <mathieu.poirier@linaro.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Will Deacon <will@kernel.org> Cc: linux-arm-kernel@lists.infradead.org Link: https://lore.kernel.org/r/20211217154521.80603-7-german.gomez@arm.com Signed-off-by: German Gomez <german.gomez@arm.com> [ Rename machine__normalize_is() to machine__normalized_is(), as suggested by James Clark ] Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com> 2021-12-17 15:45:20 +00:00			`/* SPDX-License-Identifier: GPL-2.0 */`
			`#ifndef __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H`
			`#define __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H`

			`#include "event.h"`
			`#include "thread.h"`

			`u64 get_leaf_frame_caller_aarch64(struct perf_sample sample, struct thread thread, int user_idx);`

			`#endif /* __PERF_ARM_FRAME_POINTER_UNWIND_SUPPORT_H */`