| Message ID | cover.1680954589.git.pengdonglin@sangfor.com.cn (mailing list archive) |
|---|---|
| Headers | show |
| Series | function_graph: Support recording and printing the return value of function | expand |
On Sat, 8 Apr 2023 05:42:14 -0700 Donglin Peng <pengdonglin@sangfor.com.cn> wrote: > When using the function_graph tracer to analyze system call failures, > it can be time-consuming to analyze the trace logs and locate the kernel > function that first returns an error. This change aims to simplify the > process by recording the function return value to the 'retval' member of > 'ftrace_graph_ent' and printing it when outputing the trace log. > > Note that even if a function's return type is void, a return value will > still be printed, so it should be ignored. If you care about this, the > BTF file can be used to obtain the details of function return type. We > can implement a tool to process the trace log and display the return > value based on its actual type. > > Here is an example: > > I like this series, but since the merge window for 6.4 just opened, I'm going to hold off and pull this in for the 6.5 series (after a bit more review and testing). -- Steve
When using the function_graph tracer to analyze system call failures, it can be time-consuming to analyze the trace logs and locate the kernel function that first returns an error. This change aims to simplify the process by recording the function return value to the 'retval' member of 'ftrace_graph_ent' and printing it when outputing the trace log. Note that even if a function's return type is void, a return value will still be printed, so it should be ignored. If you care about this, the BTF file can be used to obtain the details of function return type. We can implement a tool to process the trace log and display the return value based on its actual type. Here is an example: ... 1) | cgroup_attach_task() { 1) | cgroup_migrate_add_src() { 1) 1.403 us | cset_cgroup_from_root(); /* = 0xffff93fc86f58010 */ 1) 2.154 us | } /* cgroup_migrate_add_src = 0xffffb286c1297d00 */ 1) ! 386.538 us | cgroup_migrate_prepare_dst(); /* = 0x0 */ 1) | cgroup_migrate() { 1) 0.651 us | cgroup_migrate_add_task(); /* = 0xffff93fcfd346c00 */ 1) | cgroup_migrate_execute() { 1) | cpu_cgroup_can_attach() { 1) | cgroup_taskset_first() { 1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */ 1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */ 1) 0.380 us | sched_rt_can_attach(); /* = 0x0 */ 1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */ 1) 4.369 us | } /* cgroup_migrate_execute = -22 */ 1) 7.143 us | } /* cgroup_migrate = -22 */ 1) | cgroup_migrate_finish() { 1) 0.411 us | put_css_set_locked(); /* = 0x8 */ 1) + 62.397 us | put_css_set_locked(); /* = 0x80000001 */ 1) + 64.742 us | } /* cgroup_migrate_finish = 0x80000000 */ 1) ! 465.605 us | } /* cgroup_attach_task = -22 */ ... After processing the above trace logs using BTF information: ... 1) | cgroup_attach_task() { 1) | cgroup_migrate_add_src() { 1) 1.403 us | cset_cgroup_from_root(); /* = 0xffff93fc86f58010 */ 1) 2.154 us | } /* cgroup_migrate_add_src */ 1) ! 386.538 us | cgroup_migrate_prepare_dst(); /* = 0 */ 1) | cgroup_migrate() { 1) 0.651 us | cgroup_migrate_add_task(); 1) | cgroup_migrate_execute() { 1) | cpu_cgroup_can_attach() { 1) | cgroup_taskset_first() { 1) 0.732 us | cgroup_taskset_next(); /* = 0xffff93fc8fb20000 */ 1) 1.232 us | } /* cgroup_taskset_first = 0xffff93fc8fb20000 */ 1) 0.380 us | sched_rt_can_attach(); /* = 0 */ 1) 2.335 us | } /* cpu_cgroup_can_attach = -22 */ 1) 4.369 us | } /* cgroup_migrate_execute = -22 */ 1) 7.143 us | } /* cgroup_migrate = -22 */ 1) | cgroup_migrate_finish() { 1) 0.411 us | put_css_set_locked(); 1) + 62.397 us | put_css_set_locked(); 1) + 64.742 us | } /* cgroup_migrate_finish */ 1) ! 465.605 us | } /* cgroup_attach_task = -22 */ ... --- v11: - Add a limitation discovered by Mark. - Fix selftest issues. v10: - Fix code style issues for LoongArch - Fix selftest issues - Use CONFIG_FUNCTION_GRAPH_TRACER to control fgraph_ret_regs definition v9: - Fix align issues in ARM asm code - Fix align issues in LoongArch asm code - Update commit messages - Update comments for ftrace_return_to_handler v8: - Fix issues in ARM64 asm code - Fix issues in selftest - Add some comments on CONFIG_HAVE_FUNCTION_GRAPH_RETVAL - Make CONFIG_FUNCTION_GRAPH_RETVAL switable - Modify the control range of CONFIG_HAVE_FUNCTION_GRAPH_RETVAL v7: - Rename trace option 'graph_retval_hex' to 'funcgraph-retval-hex' - Introduce a new structure fgraph_ret_regs for each architecture to hold return registers - Separate each architecture modification info individual patches - Add a test case for funcgraph-retval - Update documentation description - Support LoongArch v6: - Remove the conversion code for short and char types, because these two types are rarely used to store an error code. - Modify the limitations for funcgraph-retval - Optimize the English expression v5: - Pass both the return values to ftrace_return_to_handler - Modify the parameter sequence of ftrace_return_to_handler to decrease the modification of assembly code, thanks to Russell King - Wrap __ftrace_return_to_handler with ftrace_return_to_handler for compatible - Describe the limitations of funcgraph-retval v4: - Modify commit message - Introduce new option graph_retval_hex to control display format - Introduce macro CONFIG_FUNCTION_GRAPH_RETVAL and CONFIG_HAVE_FUNCTION_GRAPH_RETVAL - Add related arch maintainers to review v3: - Modify the commit message: add trace logs processed with the btf tool v2: - Modify the commit message: use BTF to get the return type of function Donglin Peng (8): function_graph: Support recording and printing the return value of function tracing: Add documentation for funcgraph-retval and funcgraph-retval-hex ARM: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL arm64: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL riscv: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL x86/ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL LoongArch: ftrace: Enable HAVE_FUNCTION_GRAPH_RETVAL selftests/ftrace: Add funcgraph-retval test case Documentation/trace/ftrace.rst | 126 ++++++++++++++++++ arch/arm/Kconfig | 1 + arch/arm/include/asm/ftrace.h | 22 +++ arch/arm/kernel/asm-offsets.c | 8 +- arch/arm/kernel/entry-ftrace.S | 10 +- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/ftrace.h | 22 +++ arch/arm64/kernel/asm-offsets.c | 13 ++ arch/arm64/kernel/entry-ftrace.S | 27 ++-- arch/loongarch/Kconfig | 1 + arch/loongarch/include/asm/ftrace.h | 22 +++ arch/loongarch/kernel/asm-offsets.c | 15 ++- arch/loongarch/kernel/mcount.S | 14 +- arch/loongarch/kernel/mcount_dyn.S | 15 ++- arch/riscv/Kconfig | 1 + arch/riscv/include/asm/ftrace.h | 21 +++ arch/riscv/kernel/mcount.S | 7 +- arch/x86/Kconfig | 1 + arch/x86/include/asm/ftrace.h | 20 +++ arch/x86/kernel/ftrace_32.S | 8 +- arch/x86/kernel/ftrace_64.S | 7 +- include/linux/ftrace.h | 3 + kernel/trace/Kconfig | 15 +++ kernel/trace/fgraph.c | 23 +++- kernel/trace/trace.h | 2 + kernel/trace/trace_entries.h | 26 ++++ kernel/trace/trace_functions_graph.c | 93 +++++++++++-- .../ftrace/test.d/ftrace/fgraph-retval.tc | 44 ++++++ 28 files changed, 513 insertions(+), 55 deletions(-) create mode 100644 tools/testing/selftests/ftrace/test.d/ftrace/fgraph-retval.tc