From: Nathan Chancellor <nathan@kernel.org> To: Maria Yu <quic_aiquny@quicinc.com> Cc: linux@armlinux.org.uk, ardb@kernel.org, mhiramat@kernel.org, kernel@quicinc.com, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, quic_lijuang@quicinc.com, stable@vger.kernel.org Subject: Re: [PATCH v2 1/1] ARM: kprobes: Explicitly reserve r7 for local variables Date: Thu, 16 Nov 2023 10:24:18 -0700 [thread overview] Message-ID: <20231116172418.GA174808@dev-arch.thelio-3990X> (raw) In-Reply-To: <20231115095830.20607-1-quic_aiquny@quicinc.com> On Wed, Nov 15, 2023 at 05:58:30PM +0800, Maria Yu wrote: > Registers r7 is removed in clobber list, so compiler may choose r7 for > local variables usage, while r7 will be actually updated by the inline asm > code. This caused the runtime behavior wrong. > While those kind of reserved registers cannot be set to clobber list > because of error like "inline asm clobber list contains reserved > registers". > Explicitly reserve r7 by adding attribute no-omit-frame-pointer for needed > function, then in T32 asm code r7 is used as a frame pointer and is not > available for use as a general-purpose register. > Note that "no-omit-frame-pointer" will make the code size a little bigger > to store the stack frame pointer. So limited to needed functions can have > the less impact than the full source file. > > Fixes: dd12e97f3c72 ("ARM: kprobes: treat R7 as the frame pointer register in Thumb2 builds") > Signed-off-by: Maria Yu <quic_aiquny@quicinc.com> > Cc: stable@vger.kernel.org This causes warnings with clang: arch/arm/probes/kprobes/actions-thumb.c:441:47: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes] 441 | static unsigned long __kprobes __attribute__((optimize("no-omit-frame-pointer"))) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/arm/probes/kprobes/actions-thumb.c:524:38: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes] 524 | static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/arm/probes/kprobes/actions-thumb.c:560:38: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes] 560 | static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/arm/probes/kprobes/actions-thumb.c:579:38: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes] 579 | static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4 warnings generated. Furthermore, as far as I am aware, the optimize attribute has other issues so its use is discouraged, see commits 080b6f407635 ("bpf: Don't rely on GCC __attribute__((optimize)) to disable GCSE") and a7223f5bfcae ("powerpc: Avoid broken GCC __attribute__((optimize))"). Cheers, Nathan > --- > arch/arm/probes/kprobes/actions-thumb.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/arm/probes/kprobes/actions-thumb.c b/arch/arm/probes/kprobes/actions-thumb.c > index 51624fc263fc..c2fdaf9f6dba 100644 > --- a/arch/arm/probes/kprobes/actions-thumb.c > +++ b/arch/arm/probes/kprobes/actions-thumb.c > @@ -438,7 +438,7 @@ t16_simulate_branch(probes_opcode_t insn, > regs->ARM_pc = pc + (offset * 2); > } > > -static unsigned long __kprobes > +static unsigned long __kprobes __attribute__((optimize("no-omit-frame-pointer"))) > t16_emulate_loregs(probes_opcode_t insn, > struct arch_probes_insn *asi, struct pt_regs *regs) > { > @@ -521,7 +521,7 @@ t16_decode_hiregs(probes_opcode_t insn, struct arch_probes_insn *asi, > return INSN_GOOD; > } > > -static void __kprobes > +static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) > t16_emulate_push(probes_opcode_t insn, > struct arch_probes_insn *asi, struct pt_regs *regs) > { > @@ -557,7 +557,7 @@ t16_decode_push(probes_opcode_t insn, struct arch_probes_insn *asi, > return INSN_GOOD; > } > > -static void __kprobes > +static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) > t16_emulate_pop_nopc(probes_opcode_t insn, > struct arch_probes_insn *asi, struct pt_regs *regs) > { > @@ -576,7 +576,7 @@ t16_emulate_pop_nopc(probes_opcode_t insn, > ); > } > > -static void __kprobes > +static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) > t16_emulate_pop_pc(probes_opcode_t insn, > struct arch_probes_insn *asi, struct pt_regs *regs) > { > > base-commit: 9bacdd8996c77c42ca004440be610692275ff9d0 > -- > 2.17.1 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
WARNING: multiple messages have this Message-ID (diff)
From: Nathan Chancellor <nathan@kernel.org> To: Maria Yu <quic_aiquny@quicinc.com> Cc: linux@armlinux.org.uk, ardb@kernel.org, mhiramat@kernel.org, kernel@quicinc.com, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-kernel@vger.kernel.org, quic_lijuang@quicinc.com, stable@vger.kernel.org Subject: Re: [PATCH v2 1/1] ARM: kprobes: Explicitly reserve r7 for local variables Date: Thu, 16 Nov 2023 10:24:18 -0700 [thread overview] Message-ID: <20231116172418.GA174808@dev-arch.thelio-3990X> (raw) In-Reply-To: <20231115095830.20607-1-quic_aiquny@quicinc.com> On Wed, Nov 15, 2023 at 05:58:30PM +0800, Maria Yu wrote: > Registers r7 is removed in clobber list, so compiler may choose r7 for > local variables usage, while r7 will be actually updated by the inline asm > code. This caused the runtime behavior wrong. > While those kind of reserved registers cannot be set to clobber list > because of error like "inline asm clobber list contains reserved > registers". > Explicitly reserve r7 by adding attribute no-omit-frame-pointer for needed > function, then in T32 asm code r7 is used as a frame pointer and is not > available for use as a general-purpose register. > Note that "no-omit-frame-pointer" will make the code size a little bigger > to store the stack frame pointer. So limited to needed functions can have > the less impact than the full source file. > > Fixes: dd12e97f3c72 ("ARM: kprobes: treat R7 as the frame pointer register in Thumb2 builds") > Signed-off-by: Maria Yu <quic_aiquny@quicinc.com> > Cc: stable@vger.kernel.org This causes warnings with clang: arch/arm/probes/kprobes/actions-thumb.c:441:47: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes] 441 | static unsigned long __kprobes __attribute__((optimize("no-omit-frame-pointer"))) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/arm/probes/kprobes/actions-thumb.c:524:38: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes] 524 | static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/arm/probes/kprobes/actions-thumb.c:560:38: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes] 560 | static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ arch/arm/probes/kprobes/actions-thumb.c:579:38: warning: unknown attribute 'optimize' ignored [-Wunknown-attributes] 579 | static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 4 warnings generated. Furthermore, as far as I am aware, the optimize attribute has other issues so its use is discouraged, see commits 080b6f407635 ("bpf: Don't rely on GCC __attribute__((optimize)) to disable GCSE") and a7223f5bfcae ("powerpc: Avoid broken GCC __attribute__((optimize))"). Cheers, Nathan > --- > arch/arm/probes/kprobes/actions-thumb.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/arch/arm/probes/kprobes/actions-thumb.c b/arch/arm/probes/kprobes/actions-thumb.c > index 51624fc263fc..c2fdaf9f6dba 100644 > --- a/arch/arm/probes/kprobes/actions-thumb.c > +++ b/arch/arm/probes/kprobes/actions-thumb.c > @@ -438,7 +438,7 @@ t16_simulate_branch(probes_opcode_t insn, > regs->ARM_pc = pc + (offset * 2); > } > > -static unsigned long __kprobes > +static unsigned long __kprobes __attribute__((optimize("no-omit-frame-pointer"))) > t16_emulate_loregs(probes_opcode_t insn, > struct arch_probes_insn *asi, struct pt_regs *regs) > { > @@ -521,7 +521,7 @@ t16_decode_hiregs(probes_opcode_t insn, struct arch_probes_insn *asi, > return INSN_GOOD; > } > > -static void __kprobes > +static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) > t16_emulate_push(probes_opcode_t insn, > struct arch_probes_insn *asi, struct pt_regs *regs) > { > @@ -557,7 +557,7 @@ t16_decode_push(probes_opcode_t insn, struct arch_probes_insn *asi, > return INSN_GOOD; > } > > -static void __kprobes > +static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) > t16_emulate_pop_nopc(probes_opcode_t insn, > struct arch_probes_insn *asi, struct pt_regs *regs) > { > @@ -576,7 +576,7 @@ t16_emulate_pop_nopc(probes_opcode_t insn, > ); > } > > -static void __kprobes > +static void __kprobes __attribute__((optimize("no-omit-frame-pointer"))) > t16_emulate_pop_pc(probes_opcode_t insn, > struct arch_probes_insn *asi, struct pt_regs *regs) > { > > base-commit: 9bacdd8996c77c42ca004440be610692275ff9d0 > -- > 2.17.1 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel _______________________________________________ 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:[~2023-11-16 17:24 UTC|newest] Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top 2023-11-15 9:58 [PATCH v2 1/1] ARM: kprobes: Explicitly reserve r7 for local variables Maria Yu 2023-11-15 9:58 ` Maria Yu 2023-11-16 11:11 ` Ard Biesheuvel 2023-11-16 11:11 ` Ard Biesheuvel 2023-11-16 17:24 ` Nathan Chancellor [this message] 2023-11-16 17:24 ` Nathan Chancellor 2023-11-16 17:36 ` Ard Biesheuvel 2023-11-16 17:36 ` Ard Biesheuvel 2023-11-20 2:00 ` Aiqun(Maria) Yu 2023-11-20 2:00 ` Aiqun(Maria) Yu
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