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Date: Thu, 22 May 2014 17:11:38 -0700 From: Kevin Hilman <khilman@...aro.org> To: Christopher Covington <cov@...eaurora.org> Cc: Larry Bassel <larry.bassel@...aro.org>, catalin.marinas@....com, will.deacon@....com, linaro-kernel@...ts.linaro.org, linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org, mark.rutland@....com Subject: Re: [PATCH v4 2/2] arm64: enable context tracking +Mark Rutland Christopher Covington <cov@...eaurora.org> writes: > Hi Larry, > > On 05/22/2014 03:27 PM, Larry Bassel wrote: >> Make calls to ct_user_enter when the kernel is exited >> and ct_user_exit when the kernel is entered (in el0_da, >> el0_ia, el0_svc, el0_irq and all of the "error" paths). >> >> These macros expand to function calls which will only work >> properly if el0_sync and related code has been rearranged >> (in a previous patch of this series). >> >> The calls to ct_user_exit are made after hw debugging has been >> enabled (enable_dbg_and_irq). >> >> The call to ct_user_enter is made at the beginning of the >> kernel_exit macro. >> >> This patch is based on earlier work by Kevin Hilman. >> Save/restore optimizations were also done by Kevin. > >> --- a/arch/arm64/kernel/entry.S >> +++ b/arch/arm64/kernel/entry.S >> @@ -30,6 +30,44 @@ >> #include <asm/unistd32.h> >> >> /* >> + * Context tracking subsystem. Used to instrument transitions >> + * between user and kernel mode. >> + */ >> + .macro ct_user_exit, restore = 0 >> +#ifdef CONFIG_CONTEXT_TRACKING >> + bl context_tracking_user_exit >> + .if \restore == 1 >> + /* >> + * Save/restore needed during syscalls. Restore syscall arguments from >> + * the values already saved on stack during kernel_entry. >> + */ >> + ldp x0, x1, [sp] >> + ldp x2, x3, [sp, #S_X2] >> + ldp x4, x5, [sp, #S_X4] >> + ldp x6, x7, [sp, #S_X6] >> + .endif >> +#endif >> + .endm >> + >> + .macro ct_user_enter, save = 0 >> +#ifdef CONFIG_CONTEXT_TRACKING >> + .if \save == 1 >> + /* >> + * Save/restore only needed on syscall fastpath, which uses >> + * x0-x2. >> + */ >> + push x2, x3 > > Why is x3 saved? I'll respond here since I worked with Larry on the context save/restore part. [insert rather embarassing disclamer of ignorance of arm64 assembly] Based on my reading of the code, I figured only x0-x2 needed to be saved. However, based on some experiments with intentionally clobbering the registers[1] (as suggested by Mark Rutland) in order to make sure we're saving/restoring the right things, I discovered x3 was needed too (I missed updating the comment to mention x0-x3.) Maybe Will/Catalin/Mark R. can shed some light here? Kevin [1] >From 8a8702b4d597d08def22221368beae5db2f4a8aa Mon Sep 17 00:00:00 2001 From: Kevin Hilman <khilman@...aro.org> Date: Fri, 9 May 2014 13:37:43 -0700 Subject: [PATCH] KJH: test: clobber regs --- arch/arm64/kernel/entry.S | 38 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 38 insertions(+) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 520da4c02ece..232f0200e88d 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -36,6 +36,25 @@ .macro ct_user_exit, restore = 0 #ifdef CONFIG_CONTEXT_TRACKING bl context_tracking_user_exit + movz x0, #0xff, lsl #48 + movz x1, #0xff, lsl #48 + movz x2, #0xff, lsl #48 + movz x3, #0xff, lsl #48 + movz x4, #0xff, lsl #48 + movz x5, #0xff, lsl #48 + movz x6, #0xff, lsl #48 + movz x7, #0xff, lsl #48 + movz x8, #0xff, lsl #48 + movz x9, #0xff, lsl #48 + movz x10, #0xff, lsl #48 + movz x11, #0xff, lsl #48 + movz x12, #0xff, lsl #48 + movz x13, #0xff, lsl #48 + movz x14, #0xff, lsl #48 + movz x15, #0xff, lsl #48 + movz x16, #0xff, lsl #48 + movz x17, #0xff, lsl #48 + movz x18, #0xff, lsl #48 .if \restore == 1 /* * Save/restore needed during syscalls. Restore syscall arguments from @@ -60,6 +79,25 @@ push x0, x1 .endif bl context_tracking_user_enter + movz x0, #0xff, lsl #48 + movz x1, #0xff, lsl #48 + movz x2, #0xff, lsl #48 + movz x3, #0xff, lsl #48 + movz x4, #0xff, lsl #48 + movz x5, #0xff, lsl #48 + movz x6, #0xff, lsl #48 + movz x7, #0xff, lsl #48 + movz x8, #0xff, lsl #48 + movz x9, #0xff, lsl #48 + movz x10, #0xff, lsl #48 + movz x11, #0xff, lsl #48 + movz x12, #0xff, lsl #48 + movz x13, #0xff, lsl #48 + movz x14, #0xff, lsl #48 + movz x15, #0xff, lsl #48 + movz x16, #0xff, lsl #48 + movz x17, #0xff, lsl #48 + movz x18, #0xff, lsl #48 .if \save == 1 pop x0, x1 pop x2, x3 -- 1.9.2 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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