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perf test: Make leafloop workload immune to compiler options

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Since the leafloop test program was moved into the main Perf binary as a
workload, it inherited the same compiler options as Perf. In this case
the -fstack-protector option broke the assumption that simple leaf
frames don't have a stack frame on Arm. This causes
test_arm_callgraph_fp.sh to pass even if the stack isn't augmented with
the link register, making the test useless.

Fix it by rewriting the leaf function in assembly seeing as it's so
simple. Adding -fno-stack-protector would also work, but wouldn't be
robust against other future compiler option additions.

The local variables and 'a' variable were never needed so remove them to
simplify.

Reviewed-by: Ian Rogers <irogers@google.com>
Assisted-by: GitHub-Copilot:GPT-5.5
Signed-off-by: James Clark <james.clark@linaro.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
James Clark 2026-05-11 10:19:35 +01:00 committed by Arnaldo Carvalho de Melo
parent f864466690
commit 6f31bb737e
1 changed files with 31 additions and 9 deletions
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40
tools/perf/tests/workloads/leafloop.c
View File

@ -6,26 +6,48 @@
#include "../tests.h"
/* We want to check these symbols in perf script */
noinline void leaf(volatile int b);
noinline void parent(volatile int b);
noinline void leaf(void);
noinline void parent(void);
static volatile int a;
static volatile sig_atomic_t done;
static volatile sig_atomic_t done asm("leafloop_done");
static void sighandler(int sig __maybe_unused)
{
done = 1;
}
noinline void leaf(volatile int b)
#if defined(__aarch64__)
/*
* Write leaf() in assembly so it stays as a minimal leaf function with no
* stack frame and won't get silently broken in the future by any Perf wide
* compilation options like -fstack-protector-all.
*/
asm(
".pushsection .text,\"ax\",%progbits\n"
".global leaf\n"
".type leaf, %function\n"
"leaf:\n"
" adrp x1, leafloop_done\n"
" ldr w2, [x1, #:lo12:leafloop_done]\n"
" cbz w2, leaf\n"
" ret\n"
".size leaf, .-leaf\n"
".popsection\n"
);
#else
noinline void leaf(void)
{
while (!done)
a += b;
;
}
noinline void parent(volatile int b)
#endif
noinline void parent(void)
{
leaf(b);
leaf();
}
static int leafloop(int argc, const char **argv)
@ -39,7 +61,7 @@ static int leafloop(int argc, const char **argv)
signal(SIGALRM, sighandler);
alarm(sec);
parent(sec);
parent();
return 0;
}