From 1f35cd65386e02430546727bd3cc2508d052e3ec Mon Sep 17 00:00:00 2001 From: Adrian Hunter Date: Wed, 9 Jan 2019 11:18:34 +0200 Subject: [PATCH] perf thread-stack: Improve thread_stack__no_call_return() Improve thread_stack__no_call_return() to better handle 'returns' that do not match the stack i.e. 'no call'. See code comments for details. The example below shows how retpolines are affected: Example: $ cat simple-retpoline.c __attribute__((noinline)) int bar(void) { return -1; } int foo(void) { return bar() + 1; } __attribute__((indirect_branch("thunk"))) int main() { int (*volatile fn)(void) = foo; fn(); return fn(); } $ gcc -ggdb3 -Wall -Wextra -O2 -o simple-retpoline simple-retpoline.c $ objdump -d simple-retpoline 0000000000001040
: 1040: 48 83 ec 18 sub $0x18,%rsp 1044: 48 8d 05 25 01 00 00 lea 0x125(%rip),%rax # 1170 104b: 48 89 44 24 08 mov %rax,0x8(%rsp) 1050: 48 8b 44 24 08 mov 0x8(%rsp),%rax 1055: e8 1f 01 00 00 callq 1179 <__x86_indirect_thunk_rax> 105a: 48 8b 44 24 08 mov 0x8(%rsp),%rax 105f: 48 83 c4 18 add $0x18,%rsp 1063: e9 11 01 00 00 jmpq 1179 <__x86_indirect_thunk_rax> 0000000000001160 : 1160: b8 ff ff ff ff mov $0xffffffff,%eax 1165: c3 retq 0000000000001170 : 1170: e8 eb ff ff ff callq 1160 1175: 83 c0 01 add $0x1,%eax 1178: c3 retq 0000000000001179 <__x86_indirect_thunk_rax>: 1179: e8 07 00 00 00 callq 1185 <__x86_indirect_thunk_rax+0xc> 117e: f3 90 pause 1180: 0f ae e8 lfence 1183: eb f9 jmp 117e <__x86_indirect_thunk_rax+0x5> 1185: 48 89 04 24 mov %rax,(%rsp) 1189: c3 retq $ perf record -o simple-retpoline.perf.data -e intel_pt/cyc/u ./simple-retpoline [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0,017 MB simple-retpoline.perf.data ] $ perf script -i simple-retpoline.perf.data --itrace=be -s ~/libexec/perf-core/scripts/python/export-to-sqlite.py simple-retpoline.db branches calls 2019-01-08 14:03:37.851655 Creating database... 2019-01-08 14:03:37.863256 Writing records... 2019-01-08 14:03:38.069750 Adding indexes 2019-01-08 14:03:38.078799 Done $ ~/libexec/perf-core/scripts/python/exported-sql-viewer.py simple-retpoline.db Before: main -> __x86_indirect_thunk_rax -> __x86_indirect_thunk_rax -> __x86_indirect_thunk_rax -> bar After: main -> __x86_indirect_thunk_rax -> __x86_indirect_thunk_rax -> foo -> bar Committer testing: Chose "Reports", Then "Context-Sensitive Call Graph" and then go on expanding: Before: simple-retpolin PID:PID _start _start __libc_start_main main __x86_indirect_thunk_rax __x86_indirect_thunk_rax bar After: Remove the "simple.retpoline.db" file, run again the 'perf script' line to regenerate the .db file and run the exported-sql-viewer.py again to get the same all the way to 'main', then, from there, including 'main': main __x86_indirect_thunk_rax __x86_indirect_thunk_rax foo bar Signed-off-by: Adrian Hunter Tested-by: Arnaldo Carvalho de Melo Acked-by: Jiri Olsa Link: http://lkml.kernel.org/r/20190109091835.5570-6-adrian.hunter@intel.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/thread-stack.c | 49 +++++++++++++++++++++++++++++++++++++++--- 1 file changed, 46 insertions(+), 3 deletions(-) diff --git a/tools/perf/util/thread-stack.c b/tools/perf/util/thread-stack.c index f52c0f90915d..632c07a125ab 100644 --- a/tools/perf/util/thread-stack.c +++ b/tools/perf/util/thread-stack.c @@ -638,14 +638,57 @@ static int thread_stack__no_call_return(struct thread *thread, else parent = root; - /* This 'return' had no 'call', so push and pop top of stack */ - cp = call_path__findnew(cpr, parent, fsym, ip, ks); + if (parent->sym == from_al->sym) { + /* + * At the bottom of the stack, assume the missing 'call' was + * before the trace started. So, pop the current symbol and push + * the 'to' symbol. + */ + if (ts->cnt == 1) { + err = thread_stack__call_return(thread, ts, --ts->cnt, + tm, ref, false); + if (err) + return err; + } + + if (!ts->cnt) { + cp = call_path__findnew(cpr, root, tsym, addr, ks); + + return thread_stack__push_cp(ts, addr, tm, ref, cp, + true, false); + } + + /* + * Otherwise assume the 'return' is being used as a jump (e.g. + * retpoline) and just push the 'to' symbol. + */ + cp = call_path__findnew(cpr, parent, tsym, addr, ks); + + err = thread_stack__push_cp(ts, 0, tm, ref, cp, true, false); + if (!err) + ts->stack[ts->cnt - 1].non_call = true; + + return err; + } + + /* + * Assume 'parent' has not yet returned, so push 'to', and then push and + * pop 'from'. + */ + + cp = call_path__findnew(cpr, parent, tsym, addr, ks); err = thread_stack__push_cp(ts, addr, tm, ref, cp, true, false); if (err) return err; - return thread_stack__pop_cp(thread, ts, addr, tm, ref, tsym); + cp = call_path__findnew(cpr, cp, fsym, ip, ks); + + err = thread_stack__push_cp(ts, ip, tm, ref, cp, true, false); + if (err) + return err; + + return thread_stack__call_return(thread, ts, --ts->cnt, tm, ref, false); } static int thread_stack__trace_begin(struct thread *thread, -- 2.11.0