From mboxrd@z Thu Jan 1 00:00:00 1970 From: will.deacon@arm.com (Will Deacon) Date: Fri, 17 Jan 2014 10:07:23 +0000 Subject: [PATCH] ARM64: perf: support dwarf unwinding in compat mode In-Reply-To: References: <1389869123-5884-1-git-send-email-jean.pihet@linaro.org> <20140116115634.GE30257@mudshark.cambridge.arm.com> <20140116125727.GI30257@mudshark.cambridge.arm.com> Message-ID: <20140117100723.GB16003@mudshark.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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