| Message ID | 20220424154028.1698685-3-xukuohai@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | bpf trampoline for arm64 | expand |
On Sun, 24 Apr 2022 11:40:23 -0400 Xu Kuohai <xukuohai@huawei.com> wrote: > diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c > index abcadbe933bb..d2eff2b1d743 100644 > --- a/kernel/trace/trace_selftest.c > +++ b/kernel/trace/trace_selftest.c > @@ -785,8 +785,24 @@ static struct fgraph_ops fgraph_ops __initdata = { > }; > > #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > +#ifdef CONFIG_ARM64 Please find a way to add this in arm specific code. Do not add architecture defines in generic code. You could add: #ifndef ARCH_HAVE_FTRACE_DIRECT_TEST_FUNC noinline __noclone static void trace_direct_tramp(void) { } #endif here, and in arch/arm64/include/ftrace.h #define ARCH_HAVE_FTRACE_DIRECT_TEST_FUNC and define your test function in the arm64 specific code. -- Steve > +extern void trace_direct_tramp(void); > + > +asm ( > +" .pushsection .text, \"ax\", @progbits\n" > +" .type trace_direct_tramp, %function\n" > +" .global trace_direct_tramp\n" > +"trace_direct_tramp:" > +" mov x10, x30\n" > +" mov x30, x9\n" > +" ret x10\n" > +" .size trace_direct_tramp, .-trace_direct_tramp\n" > +" .popsection\n" > +); > +#else > noinline __noclone static void trace_direct_tramp(void) { } > #endif > +#endif > > /* > * Pretty much the same than for the function tracer from which the selftest
On 4/25/2022 11:05 PM, Steven Rostedt wrote: > On Sun, 24 Apr 2022 11:40:23 -0400 > Xu Kuohai <xukuohai@huawei.com> wrote: > >> diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c >> index abcadbe933bb..d2eff2b1d743 100644 >> --- a/kernel/trace/trace_selftest.c >> +++ b/kernel/trace/trace_selftest.c >> @@ -785,8 +785,24 @@ static struct fgraph_ops fgraph_ops __initdata = { >> }; >> >> #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS >> +#ifdef CONFIG_ARM64 > > Please find a way to add this in arm specific code. Do not add architecture > defines in generic code. > > You could add: > > #ifndef ARCH_HAVE_FTRACE_DIRECT_TEST_FUNC > noinline __noclone static void trace_direct_tramp(void) { } > #endif > > here, and in arch/arm64/include/ftrace.h > > #define ARCH_HAVE_FTRACE_DIRECT_TEST_FUNC > > and define your test function in the arm64 specific code. > > -- Steve > > will move this to arch/arm64/ in v4, thanks. > > >> +extern void trace_direct_tramp(void); >> + >> +asm ( >> +" .pushsection .text, \"ax\", @progbits\n" >> +" .type trace_direct_tramp, %function\n" >> +" .global trace_direct_tramp\n" >> +"trace_direct_tramp:" >> +" mov x10, x30\n" >> +" mov x30, x9\n" >> +" ret x10\n" >> +" .size trace_direct_tramp, .-trace_direct_tramp\n" >> +" .popsection\n" >> +); >> +#else >> noinline __noclone static void trace_direct_tramp(void) { } >> #endif >> +#endif >> >> /* >> * Pretty much the same than for the function tracer from which the selftest > > .
diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c index abcadbe933bb..d2eff2b1d743 100644 --- a/kernel/trace/trace_selftest.c +++ b/kernel/trace/trace_selftest.c @@ -785,8 +785,24 @@ static struct fgraph_ops fgraph_ops __initdata = { }; #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS +#ifdef CONFIG_ARM64 +extern void trace_direct_tramp(void); + +asm ( +" .pushsection .text, \"ax\", @progbits\n" +" .type trace_direct_tramp, %function\n" +" .global trace_direct_tramp\n" +"trace_direct_tramp:" +" mov x10, x30\n" +" mov x30, x9\n" +" ret x10\n" +" .size trace_direct_tramp, .-trace_direct_tramp\n" +" .popsection\n" +); +#else noinline __noclone static void trace_direct_tramp(void) { } #endif +#endif /* * Pretty much the same than for the function tracer from which the selftest
After direct call is enabled for arm64, ftrace selftest enters a dead loop: <trace_selftest_dynamic_test_func>: 00 bti c 01 mov x9, x30 <trace_direct_tramp>: 02 bl <trace_direct_tramp> ----------> ret | lr/x30 is 03, return to 03 | 03 mov w0, #0x0 <-----------------------------| | | | dead loop! | | | 04 ret ---- lr/x30 is still 03, go back to 03 ----| The reason is that when the direct caller trace_direct_tramp() returns to the patched function trace_selftest_dynamic_test_func(), lr is still the address after the instrumented instruction in the patched function, so when the patched function exits, it returns to itself! To fix this issue, we need to restore lr before trace_direct_tramp() exits, so rewrite a dedicated trace_direct_tramp() for arm64. Reported-by: Li Huafei <lihuafei1@huawei.com> Signed-off-by: Xu Kuohai <xukuohai@huawei.com> --- kernel/trace/trace_selftest.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+)