From: Jean-Philippe Brucker <jean-philippe@linaro.org> To: Qian Cai <cai@lca.pw> Cc: linux-arm-kernel@lists.infradead.org, bpf@vger.kernel.org, songliubraving@fb.com, andriin@fb.com, daniel@iogearbox.net, catalin.marinas@arm.com, john.fastabend@gmail.com, ast@kernel.org, zlim.lnx@gmail.com, kpsingh@chromium.org, yhs@fb.com, will@kernel.org, kafai@fb.com, sfr@canb.auug.org.au, linux-next@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH bpf-next 1/1] arm64: bpf: Add BPF exception tables Date: Thu, 30 Jul 2020 16:22:13 +0200 [thread overview] Message-ID: <20200730142213.GB1529030@myrica> (raw) In-Reply-To: <20200730122855.GA3773@lca.pw> [-- Attachment #1: Type: text/plain, Size: 1499 bytes --] On Thu, Jul 30, 2020 at 08:28:56AM -0400, Qian Cai wrote: > On Tue, Jul 28, 2020 at 05:21:26PM +0200, Jean-Philippe Brucker wrote: > > When a tracing BPF program attempts to read memory without using the > > bpf_probe_read() helper, the verifier marks the load instruction with > > the BPF_PROBE_MEM flag. Since the arm64 JIT does not currently recognize > > this flag it falls back to the interpreter. > > > > Add support for BPF_PROBE_MEM, by appending an exception table to the > > BPF program. If the load instruction causes a data abort, the fixup > > infrastructure finds the exception table and fixes up the fault, by > > clearing the destination register and jumping over the faulting > > instruction. > > > > To keep the compact exception table entry format, inspect the pc in > > fixup_exception(). A more generic solution would add a "handler" field > > to the table entry, like on x86 and s390. > > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> > > This will fail to compile on arm64, > > https://gitlab.com/cailca/linux-mm/-/blob/master/arm64.config > > arch/arm64/mm/extable.o: In function `fixup_exception': > arch/arm64/mm/extable.c:19: undefined reference to `arm64_bpf_fixup_exception' Thanks for the report, I attached a fix. Daniel, can I squash it and resend as v2 or is it too late? I'd be more confident if my patches sat a little longer on the list so arm64 folks have a chance to review them. This isn't my first silly mistake... Thanks, Jean [-- Attachment #2: 0001-arm64-bpf-Fix-build-for-CONFIG_BPF_JIT.patch --] [-- Type: text/plain, Size: 1688 bytes --] From 17d0f041b57903cb2657dde15559cd1923498337 Mon Sep 17 00:00:00 2001 From: Jean-Philippe Brucker <jean-philippe@linaro.org> Date: Thu, 30 Jul 2020 14:45:44 +0200 Subject: [PATCH] arm64: bpf: Fix build for !CONFIG_BPF_JIT Add a stub for arm64_bpf_fixup_exception() when CONFIG_BPF_JIT isn't enabled, and avoid the fixup in this case. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> --- arch/arm64/include/asm/extable.h | 9 +++++++++ arch/arm64/mm/extable.c | 3 ++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h index bcee40df1586..840a35ed92ec 100644 --- a/arch/arm64/include/asm/extable.h +++ b/arch/arm64/include/asm/extable.h @@ -22,8 +22,17 @@ struct exception_table_entry #define ARCH_HAS_RELATIVE_EXTABLE +#ifdef CONFIG_BPF_JIT int arm64_bpf_fixup_exception(const struct exception_table_entry *ex, struct pt_regs *regs); +#else /* !CONFIG_BPF_JIT */ +static inline +int arm64_bpf_fixup_exception(const struct exception_table_entry *ex, + struct pt_regs *regs) +{ + return 0; +} +#endif /* !CONFIG_BPF_JIT */ extern int fixup_exception(struct pt_regs *regs); #endif diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c index 1f42991cacdd..eee1732ab6cd 100644 --- a/arch/arm64/mm/extable.c +++ b/arch/arm64/mm/extable.c @@ -14,7 +14,8 @@ int fixup_exception(struct pt_regs *regs) if (!fixup) return 0; - if (regs->pc >= BPF_JIT_REGION_START && + if (IS_ENABLED(CONFIG_BPF_JIT) && + regs->pc >= BPF_JIT_REGION_START && regs->pc < BPF_JIT_REGION_END) return arm64_bpf_fixup_exception(fixup, regs); -- 2.27.0
WARNING: multiple messages have this Message-ID (diff)
From: Jean-Philippe Brucker <jean-philippe@linaro.org> To: Qian Cai <cai@lca.pw> Cc: sfr@canb.auug.org.au, songliubraving@fb.com, daniel@iogearbox.net, catalin.marinas@arm.com, john.fastabend@gmail.com, ast@kernel.org, linux-kernel@vger.kernel.org, will@kernel.org, linux-next@vger.kernel.org, zlim.lnx@gmail.com, kpsingh@chromium.org, yhs@fb.com, bpf@vger.kernel.org, andriin@fb.com, kafai@fb.com, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH bpf-next 1/1] arm64: bpf: Add BPF exception tables Date: Thu, 30 Jul 2020 16:22:13 +0200 [thread overview] Message-ID: <20200730142213.GB1529030@myrica> (raw) In-Reply-To: <20200730122855.GA3773@lca.pw> [-- Attachment #1: Type: text/plain, Size: 1499 bytes --] On Thu, Jul 30, 2020 at 08:28:56AM -0400, Qian Cai wrote: > On Tue, Jul 28, 2020 at 05:21:26PM +0200, Jean-Philippe Brucker wrote: > > When a tracing BPF program attempts to read memory without using the > > bpf_probe_read() helper, the verifier marks the load instruction with > > the BPF_PROBE_MEM flag. Since the arm64 JIT does not currently recognize > > this flag it falls back to the interpreter. > > > > Add support for BPF_PROBE_MEM, by appending an exception table to the > > BPF program. If the load instruction causes a data abort, the fixup > > infrastructure finds the exception table and fixes up the fault, by > > clearing the destination register and jumping over the faulting > > instruction. > > > > To keep the compact exception table entry format, inspect the pc in > > fixup_exception(). A more generic solution would add a "handler" field > > to the table entry, like on x86 and s390. > > > > Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> > > This will fail to compile on arm64, > > https://gitlab.com/cailca/linux-mm/-/blob/master/arm64.config > > arch/arm64/mm/extable.o: In function `fixup_exception': > arch/arm64/mm/extable.c:19: undefined reference to `arm64_bpf_fixup_exception' Thanks for the report, I attached a fix. Daniel, can I squash it and resend as v2 or is it too late? I'd be more confident if my patches sat a little longer on the list so arm64 folks have a chance to review them. This isn't my first silly mistake... Thanks, Jean [-- Attachment #2: 0001-arm64-bpf-Fix-build-for-CONFIG_BPF_JIT.patch --] [-- Type: text/plain, Size: 1688 bytes --] From 17d0f041b57903cb2657dde15559cd1923498337 Mon Sep 17 00:00:00 2001 From: Jean-Philippe Brucker <jean-philippe@linaro.org> Date: Thu, 30 Jul 2020 14:45:44 +0200 Subject: [PATCH] arm64: bpf: Fix build for !CONFIG_BPF_JIT Add a stub for arm64_bpf_fixup_exception() when CONFIG_BPF_JIT isn't enabled, and avoid the fixup in this case. Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org> --- arch/arm64/include/asm/extable.h | 9 +++++++++ arch/arm64/mm/extable.c | 3 ++- 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/extable.h b/arch/arm64/include/asm/extable.h index bcee40df1586..840a35ed92ec 100644 --- a/arch/arm64/include/asm/extable.h +++ b/arch/arm64/include/asm/extable.h @@ -22,8 +22,17 @@ struct exception_table_entry #define ARCH_HAS_RELATIVE_EXTABLE +#ifdef CONFIG_BPF_JIT int arm64_bpf_fixup_exception(const struct exception_table_entry *ex, struct pt_regs *regs); +#else /* !CONFIG_BPF_JIT */ +static inline +int arm64_bpf_fixup_exception(const struct exception_table_entry *ex, + struct pt_regs *regs) +{ + return 0; +} +#endif /* !CONFIG_BPF_JIT */ extern int fixup_exception(struct pt_regs *regs); #endif diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c index 1f42991cacdd..eee1732ab6cd 100644 --- a/arch/arm64/mm/extable.c +++ b/arch/arm64/mm/extable.c @@ -14,7 +14,8 @@ int fixup_exception(struct pt_regs *regs) if (!fixup) return 0; - if (regs->pc >= BPF_JIT_REGION_START && + if (IS_ENABLED(CONFIG_BPF_JIT) && + regs->pc >= BPF_JIT_REGION_START && regs->pc < BPF_JIT_REGION_END) return arm64_bpf_fixup_exception(fixup, regs); -- 2.27.0 [-- Attachment #3: Type: text/plain, Size: 176 bytes --] _______________________________________________ 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:[~2020-07-30 14:22 UTC|newest] Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-07-28 15:21 [PATCH bpf-next 0/1] arm64: Add BPF exception tables Jean-Philippe Brucker 2020-07-28 15:21 ` Jean-Philippe Brucker 2020-07-28 15:21 ` [PATCH bpf-next 1/1] arm64: bpf: " Jean-Philippe Brucker 2020-07-28 15:21 ` Jean-Philippe Brucker 2020-07-29 17:28 ` Song Liu 2020-07-29 17:28 ` Song Liu 2020-07-29 21:29 ` Daniel Borkmann 2020-07-29 21:29 ` Daniel Borkmann 2020-07-30 8:28 ` Jean-Philippe Brucker 2020-07-30 8:28 ` Jean-Philippe Brucker 2020-07-30 12:28 ` Qian Cai 2020-07-30 12:28 ` Qian Cai 2020-07-30 14:22 ` Jean-Philippe Brucker [this message] 2020-07-30 14:22 ` Jean-Philippe Brucker 2020-07-30 19:47 ` Daniel Borkmann 2020-07-30 19:47 ` Daniel Borkmann 2020-07-30 21:14 ` Jean-Philippe Brucker 2020-07-30 21:14 ` Jean-Philippe Brucker 2020-07-30 22:45 ` Daniel Borkmann 2020-07-30 22:45 ` Daniel Borkmann 2021-06-09 12:04 ` [PATCH bpf-next 0/1] arm64: " Ravi Bangoria 2021-06-09 12:04 ` Ravi Bangoria 2021-06-11 0:12 ` Alexei Starovoitov 2021-06-11 0:12 ` Alexei Starovoitov 2021-06-17 6:58 ` Ravi Bangoria 2021-06-17 6:58 ` Ravi Bangoria 2021-06-18 16:34 ` Alexei Starovoitov 2021-06-18 16:34 ` Alexei Starovoitov 2021-06-22 7:10 ` Ravi Bangoria 2021-06-22 7:10 ` Ravi Bangoria 2021-06-22 11:00 ` [PATCH] x86 bpf: Fix extable offset calculation Ravi Bangoria 2021-06-25 4:01 ` Alexei Starovoitov 2021-06-25 6:22 ` Ravi Bangoria 2021-06-25 15:07 ` Alexei Starovoitov
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