From: Mark Rutland <mark.rutland@arm.com> To: Xu Kuohai <xukuohai@huawei.com> Cc: bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>, Daniel Borkmann <daniel@iogearbox.net>, Alexei Starovoitov <ast@kernel.org>, Zi Shen Lim <zlim.lnx@gmail.com>, Andrii Nakryiko <andrii@kernel.org>, Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>, John Fastabend <john.fastabend@gmail.com>, KP Singh <kpsingh@kernel.org>, "David S . Miller" <davem@davemloft.net>, Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>, David Ahern <dsahern@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org, hpa@zytor.com, Shuah Khan <shuah@kernel.org>, Jakub Kicinski <kuba@kernel.org>, Jesper Dangaard Brouer <hawk@kernel.org>, Pasha Tatashin <pasha.tatashin@soleen.com>, Ard Biesheuvel <ardb@kernel.org>, Daniel Kiss <daniel.kiss@arm.com>, Steven Price <steven.price@arm.com>, Sudeep Holla <sudeep.holla@arm.com>, Marc Zyngier <maz@kernel.org>, Peter Collingbourne <pcc@google.com>, Mark Brown <broonie@kernel.org>, Delyan Kratunov <delyank@fb.com>, Kumar Kartikeya Dwivedi <memxor@gmail.com> Subject: Re: [PATCH bpf-next v5 2/6] ftrace: Fix deadloop caused by direct call in ftrace selftest Date: Wed, 25 May 2022 14:43:55 +0100 [thread overview] Message-ID: <Yo4ymwu92gM75/Z5@FVFF77S0Q05N> (raw) In-Reply-To: <20220518131638.3401509-3-xukuohai@huawei.com> On Wed, May 18, 2022 at 09:16:34AM -0400, Xu Kuohai wrote: > After direct call is enabled for arm64, ftrace selftest enters a > dead loop: IIUC this means that patch 1 alone is broken, and presumably this patch should have been part of it? > <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. As mentioned on patch 1 I'd prefer we solved this through indirection, which would avoid the need for this and would make things more robust generally by keeping the unusual calling convention private to the patch-site and regular trampoline. Thanks, Mark. > Reported-by: Li Huafei <lihuafei1@huawei.com> > Signed-off-by: Xu Kuohai <xukuohai@huawei.com> > --- > arch/arm64/include/asm/ftrace.h | 10 ++++++++++ > arch/arm64/kernel/entry-ftrace.S | 10 ++++++++++ > kernel/trace/trace_selftest.c | 2 ++ > 3 files changed, 22 insertions(+) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index 14a35a5df0a1..6f6b184e72fb 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -126,6 +126,16 @@ static inline bool arch_syscall_match_sym_name(const char *sym, > */ > return !strcmp(sym + 8, name); > } > + > +#ifdef CONFIG_FTRACE_SELFTEST > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > + > +#define trace_direct_tramp trace_direct_tramp > +extern void trace_direct_tramp(void); > + > +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ > +#endif /* CONFIG_FTRACE_SELFTEST */ > + > #endif /* ifndef __ASSEMBLY__ */ > > #endif /* __ASM_FTRACE_H */ > diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S > index dfe62c55e3a2..a47e87d4d3dd 100644 > --- a/arch/arm64/kernel/entry-ftrace.S > +++ b/arch/arm64/kernel/entry-ftrace.S > @@ -357,3 +357,13 @@ SYM_CODE_START(return_to_handler) > ret > SYM_CODE_END(return_to_handler) > #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > + > +#ifdef CONFIG_FTRACE_SELFTEST > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > +SYM_FUNC_START(trace_direct_tramp) > + mov x10, x30 > + mov x30, x9 > + ret x10 > +SYM_FUNC_END(trace_direct_tramp) > +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ > +#endif /* CONFIG_FTRACE_SELFTEST */ > diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c > index abcadbe933bb..e7ccd0d10c39 100644 > --- a/kernel/trace/trace_selftest.c > +++ b/kernel/trace/trace_selftest.c > @@ -785,8 +785,10 @@ static struct fgraph_ops fgraph_ops __initdata = { > }; > > #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > +#ifndef trace_direct_tramp > noinline __noclone static void trace_direct_tramp(void) { } > #endif > +#endif > > /* > * Pretty much the same than for the function tracer from which the selftest > -- > 2.30.2 >
WARNING: multiple messages have this Message-ID (diff)
From: Mark Rutland <mark.rutland@arm.com> To: Xu Kuohai <xukuohai@huawei.com> Cc: bpf@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-kselftest@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will@kernel.org>, Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>, Daniel Borkmann <daniel@iogearbox.net>, Alexei Starovoitov <ast@kernel.org>, Zi Shen Lim <zlim.lnx@gmail.com>, Andrii Nakryiko <andrii@kernel.org>, Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>, Yonghong Song <yhs@fb.com>, John Fastabend <john.fastabend@gmail.com>, KP Singh <kpsingh@kernel.org>, "David S . Miller" <davem@davemloft.net>, Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>, David Ahern <dsahern@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org, hpa@zytor.com, Shuah Khan <shuah@kernel.org>, Jakub Kicinski <kuba@kernel.org>, Jesper Dangaard Brouer <hawk@kernel.org>, Pasha Tatashin <pasha.tatashin@soleen.com>, Ard Biesheuvel <ardb@kernel.org>, Daniel Kiss <daniel.kiss@arm.com>, Steven Price <steven.price@arm.com>, Sudeep Holla <sudeep.holla@arm.com>, Marc Zyngier <maz@kernel.org>, Peter Collingbourne <pcc@google.com>, Mark Brown <broonie@kernel.org>, Delyan Kratunov <delyank@fb.com>, Kumar Kartikeya Dwivedi <memxor@gmail.com> Subject: Re: [PATCH bpf-next v5 2/6] ftrace: Fix deadloop caused by direct call in ftrace selftest Date: Wed, 25 May 2022 14:43:55 +0100 [thread overview] Message-ID: <Yo4ymwu92gM75/Z5@FVFF77S0Q05N> (raw) In-Reply-To: <20220518131638.3401509-3-xukuohai@huawei.com> On Wed, May 18, 2022 at 09:16:34AM -0400, Xu Kuohai wrote: > After direct call is enabled for arm64, ftrace selftest enters a > dead loop: IIUC this means that patch 1 alone is broken, and presumably this patch should have been part of it? > <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. As mentioned on patch 1 I'd prefer we solved this through indirection, which would avoid the need for this and would make things more robust generally by keeping the unusual calling convention private to the patch-site and regular trampoline. Thanks, Mark. > Reported-by: Li Huafei <lihuafei1@huawei.com> > Signed-off-by: Xu Kuohai <xukuohai@huawei.com> > --- > arch/arm64/include/asm/ftrace.h | 10 ++++++++++ > arch/arm64/kernel/entry-ftrace.S | 10 ++++++++++ > kernel/trace/trace_selftest.c | 2 ++ > 3 files changed, 22 insertions(+) > > diff --git a/arch/arm64/include/asm/ftrace.h b/arch/arm64/include/asm/ftrace.h > index 14a35a5df0a1..6f6b184e72fb 100644 > --- a/arch/arm64/include/asm/ftrace.h > +++ b/arch/arm64/include/asm/ftrace.h > @@ -126,6 +126,16 @@ static inline bool arch_syscall_match_sym_name(const char *sym, > */ > return !strcmp(sym + 8, name); > } > + > +#ifdef CONFIG_FTRACE_SELFTEST > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > + > +#define trace_direct_tramp trace_direct_tramp > +extern void trace_direct_tramp(void); > + > +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ > +#endif /* CONFIG_FTRACE_SELFTEST */ > + > #endif /* ifndef __ASSEMBLY__ */ > > #endif /* __ASM_FTRACE_H */ > diff --git a/arch/arm64/kernel/entry-ftrace.S b/arch/arm64/kernel/entry-ftrace.S > index dfe62c55e3a2..a47e87d4d3dd 100644 > --- a/arch/arm64/kernel/entry-ftrace.S > +++ b/arch/arm64/kernel/entry-ftrace.S > @@ -357,3 +357,13 @@ SYM_CODE_START(return_to_handler) > ret > SYM_CODE_END(return_to_handler) > #endif /* CONFIG_FUNCTION_GRAPH_TRACER */ > + > +#ifdef CONFIG_FTRACE_SELFTEST > +#ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > +SYM_FUNC_START(trace_direct_tramp) > + mov x10, x30 > + mov x30, x9 > + ret x10 > +SYM_FUNC_END(trace_direct_tramp) > +#endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */ > +#endif /* CONFIG_FTRACE_SELFTEST */ > diff --git a/kernel/trace/trace_selftest.c b/kernel/trace/trace_selftest.c > index abcadbe933bb..e7ccd0d10c39 100644 > --- a/kernel/trace/trace_selftest.c > +++ b/kernel/trace/trace_selftest.c > @@ -785,8 +785,10 @@ static struct fgraph_ops fgraph_ops __initdata = { > }; > > #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS > +#ifndef trace_direct_tramp > noinline __noclone static void trace_direct_tramp(void) { } > #endif > +#endif > > /* > * Pretty much the same than for the function tracer from which the selftest > -- > 2.30.2 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-05-25 13:44 UTC|newest] Thread overview: 60+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-05-18 13:16 [PATCH bpf-next v5 0/6] bpf trampoline for arm64 Xu Kuohai 2022-05-18 13:16 ` Xu Kuohai 2022-05-18 13:16 ` [PATCH bpf-next v5 1/6] arm64: ftrace: Add ftrace direct call support Xu Kuohai 2022-05-18 13:16 ` Xu Kuohai 2022-05-23 1:39 ` KP Singh 2022-05-23 1:39 ` KP Singh 2022-05-25 13:38 ` Mark Rutland 2022-05-25 13:38 ` Mark Rutland 2022-05-26 9:45 ` Xu Kuohai 2022-05-26 9:45 ` Xu Kuohai 2022-05-26 10:06 ` Mark Rutland 2022-05-26 10:06 ` Mark Rutland 2022-05-26 14:48 ` Xu Kuohai 2022-05-26 14:48 ` Xu Kuohai 2022-06-06 16:35 ` Mark Rutland 2022-06-06 16:35 ` Mark Rutland 2022-06-09 4:27 ` Xu Kuohai 2022-06-09 4:27 ` Xu Kuohai 2022-08-09 17:03 ` Florent Revest 2022-08-09 17:03 ` Florent Revest 2022-08-10 8:10 ` Xu Kuohai 2022-08-10 8:10 ` Xu Kuohai 2022-05-18 13:16 ` [PATCH bpf-next v5 2/6] ftrace: Fix deadloop caused by direct call in ftrace selftest Xu Kuohai 2022-05-18 13:16 ` Xu Kuohai 2022-05-25 13:43 ` Mark Rutland [this message] 2022-05-25 13:43 ` Mark Rutland 2022-05-26 9:45 ` Xu Kuohai 2022-05-26 9:45 ` Xu Kuohai 2022-05-18 13:16 ` [PATCH bpf-next v5 3/6] bpf: Remove is_valid_bpf_tramp_flags() Xu Kuohai 2022-05-18 13:16 ` Xu Kuohai 2022-05-25 13:45 ` Mark Rutland 2022-05-25 13:45 ` Mark Rutland 2022-05-26 9:45 ` Xu Kuohai 2022-05-26 9:45 ` Xu Kuohai 2022-05-26 10:12 ` Mark Rutland 2022-05-26 10:12 ` Mark Rutland 2022-05-26 14:46 ` Xu Kuohai 2022-05-26 14:46 ` Xu Kuohai 2022-05-18 13:16 ` [PATCH bpf-next v5 4/6] bpf, arm64: Impelment bpf_arch_text_poke() for arm64 Xu Kuohai 2022-05-18 13:16 ` Xu Kuohai 2022-05-23 1:41 ` KP Singh 2022-05-23 1:41 ` KP Singh 2022-05-25 14:10 ` Mark Rutland 2022-05-25 14:10 ` Mark Rutland 2022-05-26 9:45 ` Xu Kuohai 2022-05-26 9:45 ` Xu Kuohai 2022-05-26 10:34 ` Mark Rutland 2022-05-26 10:34 ` Mark Rutland 2022-05-26 14:47 ` Xu Kuohai 2022-05-26 14:47 ` Xu Kuohai 2022-05-18 13:16 ` [PATCH bpf-next v5 5/6] bpf, arm64: bpf trampoline " Xu Kuohai 2022-05-18 13:16 ` Xu Kuohai 2022-05-20 21:18 ` Alexei Starovoitov 2022-05-20 21:18 ` Alexei Starovoitov 2022-05-23 16:09 ` Mark Rutland 2022-05-23 16:09 ` Mark Rutland 2022-05-23 1:36 ` KP Singh 2022-05-23 1:36 ` KP Singh 2022-05-18 13:16 ` [PATCH bpf-next v5 6/6] selftests/bpf: Fix trivial typo in fentry_fexit.c Xu Kuohai 2022-05-18 13:16 ` Xu Kuohai
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