From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from usa-sjc-mx-foss1.foss.arm.com ([217.140.101.70]:40128 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752305AbeENLHI (ORCPT ); Mon, 14 May 2018 07:07:08 -0400 Date: Mon, 14 May 2018 12:07:03 +0100 From: Dave Martin To: Mark Rutland Cc: linux-arm-kernel@lists.infradead.org, marc.zyngier@arm.com, catalin.marinas@arm.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, linux@dominikbrodowski.net, james.morse@arm.com, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 07/18] arm64: remove sigreturn wrappers Message-ID: <20180514110702.GD7753@e103592.cambridge.arm.com> References: <20180514094640.27569-1-mark.rutland@arm.com> <20180514094640.27569-8-mark.rutland@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180514094640.27569-8-mark.rutland@arm.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Mon, May 14, 2018 at 10:46:29AM +0100, Mark Rutland wrote: > The arm64 sigreturn* syscall handlers are non-standard. Rather than > taking a number of user parameters in registers as per the AAPCS, > they expect the pt_regs as their sole argument. > > To make this work, we override the syscall definitions to invoke > wrappers written in assembly, which mov the SP into x0, and branch to > their respective C functions. > > On other architectures (such as x86), the sigreturn* functions take no > argument and instead use current_pt_regs() to acquire the user > registers. This requires less boilerplate code, and allows for other > features such as interposing C code in this path. Hmmm, I always wondered why rt_sigreturn() et al. were handled specially. If there's effectively no underlying reason for that, it makes sense to regularise the interface to these syscalls. Tentatively-reviewed-by: Dave Martin > > This patch takes the same approach for arm64. > > Signed-off-by: Mark Rutland > Cc: Catalin Marinas > Cc: Will Deacon > --- > arch/arm64/include/asm/unistd32.h | 4 ++-- > arch/arm64/kernel/entry.S | 8 -------- > arch/arm64/kernel/entry32.S | 10 ---------- > arch/arm64/kernel/signal.c | 3 ++- > arch/arm64/kernel/signal32.c | 6 ++++-- > arch/arm64/kernel/sys.c | 3 +-- > arch/arm64/kernel/sys32.c | 4 ++-- > 7 files changed, 11 insertions(+), 27 deletions(-) > > diff --git a/arch/arm64/include/asm/unistd32.h b/arch/arm64/include/asm/unistd32.h > index ef292160748c..ab95554b1734 100644 > --- a/arch/arm64/include/asm/unistd32.h > +++ b/arch/arm64/include/asm/unistd32.h > @@ -260,7 +260,7 @@ __SYSCALL(117, sys_ni_syscall) > #define __NR_fsync 118 > __SYSCALL(__NR_fsync, sys_fsync) > #define __NR_sigreturn 119 > -__SYSCALL(__NR_sigreturn, compat_sys_sigreturn_wrapper) > +__SYSCALL(__NR_sigreturn, compat_sys_sigreturn) > #define __NR_clone 120 > __SYSCALL(__NR_clone, sys_clone) > #define __NR_setdomainname 121 > @@ -368,7 +368,7 @@ __SYSCALL(__NR_getresgid, sys_getresgid16) > #define __NR_prctl 172 > __SYSCALL(__NR_prctl, sys_prctl) > #define __NR_rt_sigreturn 173 > -__SYSCALL(__NR_rt_sigreturn, compat_sys_rt_sigreturn_wrapper) > +__SYSCALL(__NR_rt_sigreturn, compat_sys_rt_sigreturn) > #define __NR_rt_sigaction 174 > __SYSCALL(__NR_rt_sigaction, compat_sys_rt_sigaction) > #define __NR_rt_sigprocmask 175 > diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S > index ec2ee720e33e..08ea3cbfb08f 100644 > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -1108,14 +1108,6 @@ __entry_tramp_data_start: > #endif /* CONFIG_UNMAP_KERNEL_AT_EL0 */ > > /* > - * Special system call wrappers. > - */ > -ENTRY(sys_rt_sigreturn_wrapper) > - mov x0, sp > - b sys_rt_sigreturn > -ENDPROC(sys_rt_sigreturn_wrapper) > - > -/* > * Register switch for AArch64. The callee-saved registers need to be saved > * and restored. On entry: > * x0 = previous task_struct (must be preserved across the switch) > diff --git a/arch/arm64/kernel/entry32.S b/arch/arm64/kernel/entry32.S > index f332d5d1f6b4..f9461696dde4 100644 > --- a/arch/arm64/kernel/entry32.S > +++ b/arch/arm64/kernel/entry32.S > @@ -30,16 +30,6 @@ > * System call wrappers for the AArch32 compatibility layer. > */ > > -ENTRY(compat_sys_sigreturn_wrapper) > - mov x0, sp > - b compat_sys_sigreturn > -ENDPROC(compat_sys_sigreturn_wrapper) > - > -ENTRY(compat_sys_rt_sigreturn_wrapper) > - mov x0, sp > - b compat_sys_rt_sigreturn > -ENDPROC(compat_sys_rt_sigreturn_wrapper) > - > ENTRY(compat_sys_statfs64_wrapper) > mov w3, #84 > cmp w1, #88 > diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c > index 8e624fec4707..caa7a68cf2d2 100644 > --- a/arch/arm64/kernel/signal.c > +++ b/arch/arm64/kernel/signal.c > @@ -538,8 +538,9 @@ static int restore_sigframe(struct pt_regs *regs, > return err; > } > > -asmlinkage long sys_rt_sigreturn(struct pt_regs *regs) > +asmlinkage long sys_rt_sigreturn(void) > { > + struct pt_regs *regs = current_pt_regs(); > struct rt_sigframe __user *frame; > > /* Always make any pending restarted system calls return -EINTR */ > diff --git a/arch/arm64/kernel/signal32.c b/arch/arm64/kernel/signal32.c > index 77b91f478995..cb10588a7cb2 100644 > --- a/arch/arm64/kernel/signal32.c > +++ b/arch/arm64/kernel/signal32.c > @@ -282,8 +282,9 @@ static int compat_restore_sigframe(struct pt_regs *regs, > return err; > } > > -asmlinkage int compat_sys_sigreturn(struct pt_regs *regs) > +asmlinkage int compat_sys_sigreturn(void) > { > + struct pt_regs *regs = current_pt_regs(); > struct compat_sigframe __user *frame; > > /* Always make any pending restarted system calls return -EINTR */ > @@ -312,8 +313,9 @@ asmlinkage int compat_sys_sigreturn(struct pt_regs *regs) > return 0; > } > > -asmlinkage int compat_sys_rt_sigreturn(struct pt_regs *regs) > +asmlinkage int compat_sys_rt_sigreturn(void) > { > + struct pt_regs *regs = current_pt_regs(); > struct compat_rt_sigframe __user *frame; > > /* Always make any pending restarted system calls return -EINTR */ > diff --git a/arch/arm64/kernel/sys.c b/arch/arm64/kernel/sys.c > index 72981bae10eb..31045f3fed92 100644 > --- a/arch/arm64/kernel/sys.c > +++ b/arch/arm64/kernel/sys.c > @@ -48,8 +48,7 @@ SYSCALL_DEFINE1(arm64_personality, unsigned int, personality) > /* > * Wrappers to pass the pt_regs argument. > */ > -asmlinkage long sys_rt_sigreturn_wrapper(void); > -#define sys_rt_sigreturn sys_rt_sigreturn_wrapper > +asmlinkage long sys_rt_sigreturn(void); > #define sys_personality sys_arm64_personality > > #undef __SYSCALL > diff --git a/arch/arm64/kernel/sys32.c b/arch/arm64/kernel/sys32.c > index a40b1343b819..1ef103c95410 100644 > --- a/arch/arm64/kernel/sys32.c > +++ b/arch/arm64/kernel/sys32.c > @@ -25,8 +25,8 @@ > #include > #include > > -asmlinkage long compat_sys_sigreturn_wrapper(void); > -asmlinkage long compat_sys_rt_sigreturn_wrapper(void); > +asmlinkage long compat_sys_sigreturn(void); > +asmlinkage long compat_sys_rt_sigreturn(void); > asmlinkage long compat_sys_statfs64_wrapper(void); > asmlinkage long compat_sys_fstatfs64_wrapper(void); > asmlinkage long compat_sys_pread64_wrapper(void); > -- > 2.11.0 > > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel