Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754174AbaATRFT (ORCPT ); Mon, 20 Jan 2014 12:05:19 -0500 Received: from mail-vc0-f179.google.com ([209.85.220.179]:62798 "EHLO mail-vc0-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751825AbaATRFP (ORCPT ); Mon, 20 Jan 2014 12:05:15 -0500 MIME-Version: 1.0 In-Reply-To: <20140117100723.GB16003@mudshark.cambridge.arm.com> References: <1389869123-5884-1-git-send-email-jean.pihet@linaro.org> <20140116115634.GE30257@mudshark.cambridge.arm.com> <20140116125727.GI30257@mudshark.cambridge.arm.com> <20140117100723.GB16003@mudshark.cambridge.arm.com> Date: Mon, 20 Jan 2014 18:05:14 +0100 Message-ID: Subject: Re: [PATCH] ARM64: perf: support dwarf unwinding in compat mode From: Jean Pihet To: Will Deacon Cc: "linux-kernel@vger.kernel.org" , "linaro-kernel@lists.linaro.org" , "linux-arm-kernel@lists.infradead.org" , Arnaldo , "patches@linaro.org" , Jiri Olsa , Ingo Molnar , Steve Capper Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Will, Here is an updated version of the change, which uses compat_sp at only one place. The drawback is that compat_user_mode is checked when calling compat_user_stack_pointer, which seems unnecessary. Unfortunately the check is not optimized out by the complier as I could check with objdump -S. What do you think? diff --git a/arch/arm64/include/asm/compat.h b/arch/arm64/include/asm/compat.h index fda2704..e71f81f 100644 --- a/arch/arm64/include/asm/compat.h +++ b/arch/arm64/include/asm/compat.h @@ -228,7 +228,7 @@ static inline compat_uptr_t ptr_to_compat(void __user *uptr) return (u32)(unsigned long)uptr; } -#define compat_user_stack_pointer() (current_pt_regs()->compat_sp) +#define compat_user_stack_pointer() (user_stack_pointer(current_pt_regs())) static inline void __user *arch_compat_alloc_user_space(long len) { diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h index fbb0020..86d5b54 100644 --- a/arch/arm64/include/asm/ptrace.h +++ b/arch/arm64/include/asm/ptrace.h @@ -133,7 +133,7 @@ struct pt_regs { (!((regs)->pstate & PSR_F_BIT)) #define user_stack_pointer(regs) \ - ((regs)->sp) + (!compat_user_mode(regs)) ? ((regs)->sp) : ((regs)->compat_sp) /* * Are the current registers suitable for user mode? (used to maintain Regards, Jean On 17 January 2014 11:07, Will Deacon wrote: > On Fri, Jan 17, 2014 at 09:00:09AM +0000, Jean Pihet wrote: >> On 16 January 2014 14:47, Jean Pihet wrote: >> >> So the simplest thing would be to make compat_user_stack_pointer expand to >> >> user_stack_pointer(current_pt_regs()) on arm64 and merge that in with your >> >> original patch fixing user_stack_pointer. >> >> I see 2 issues in your proposal: >> >> 1) user_stack_pointer(regs) calls compat_user_stack_pointer if >> compat_user_mode(regs)) and compat_user_stack_pointer expands to >> user_stack_pointer. I see a circular dependency in the macros. > > Not today it doesn't, so you just need to avoid writing the circular > dependency and instead make user_stack_pointer access (regs)->compat_sp > instead. > >> 2) current_pt_regs() returns the current task regs although perf >> passes a regs struct that had been recorded previously. > > Yes, but compat_user_stack_pointer doesn't take a regs paramater anyway, so > there's no change in behaviour here. > > Will -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/