From: arnd@arndb•de (Arnd Bergmann)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH 5/5] ARM: entry: Fix Thumb-2 undef handling for multi-CPU kernels
Date: Thu, 1 Sep 2011 16:52:12 +0200 [thread overview]
Message-ID: <201109011652.12711.arnd@arndb.de> (raw)
In-Reply-To: <1312971223-28165-6-git-send-email-dave.martin@linaro.org>
On Wednesday 10 August 2011, Dave Martin wrote:
> When v6 and >=v7 boards are supported in the same kernel, the
> __und_usr code currently makes a build-time assumption that Thumb-2
> instructions occurring in userspace don't need to be supported.
> Strictly speaking this is incorrect.
>
> This patch fixes the above case by doing a run-time check on the
> CPU architecture in these cases. This only affects kernels which
> support v6 and >=v7 CPUs together: plain v6 and plain v7 kernels
> are unaffected.
I think this patch broke random configurations (!THUMB2 && v7) for me:
> @@ -439,7 +440,27 @@ __und_usr:
> #endif
> beq call_fpe
> @ Thumb instruction
> -#if __LINUX_ARM_ARCH__ >= 7
> +#if CONFIG_ARM_THUMB && __LINUX_ARM_ARCH__ >= 6 && CONFIG_CPU_V7
> +/*
> + * Thumb-2 instruction handling. Note that because pre-v6 and >= v6 platforms
> + * can never be supported in a single kernel, this code is not applicable at
> + * all when __LINUX_ARM_ARCH__ < 6. This allows simplifying assumptions to be
> + * made about .arch directives.
> + */
> +#if __LINUX_ARM_ARCH__ < 7
> +/* If the target CPU may not be Thumb-2-capable, a run-time check is needed: */
> +#define NEED_CPU_ARCHITECTURE
> + ldr r5, .LCcpu_architecture
> + ldr r5, [r5]
> + cmp r5, #CPU_ARCH_ARMv7
> + blo __und_usr_unknown
> +/*
> + * The following code won't get run unless the running CPU really is v7, so
> + * coding round the lack of ldrht on older arches is pointless. Temporarily
> + * override the assembler target arch with the minimum required instead:
> + */
> + .arch armv6t2
> +#endif
> 2:
> ARM( ldrht r5, [r4], #2 )
This fixes it, please fold into the patch or apply on top.
Arnd
8<---
ARM: entry: refix Fix Thumb-2 undef handling for multi-CPU kernels
In some configurations labels become obsolete, so don't generate fixups for them.
Signed-off-by: Arnd Bergmann <arnd@arndb•de>
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 9ad50c4..b145f16 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S
@@ -497,7 +497,7 @@ ENDPROC(__und_usr)
.popsection
.pushsection __ex_table,"a"
.long 1b, 4b
-#if __LINUX_ARM_ARCH__ >= 7
+#if CONFIG_ARM_THUMB && __LINUX_ARM_ARCH__ >= 6 && CONFIG_CPU_V7
.long 2b, 4b
.long 3b, 4b
#endif
next prev parent reply other threads:[~2011-09-01 14:52 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-08-10 10:13 [RFC PATCH 0/5] Fix Thumb-2 undef handling for mixed-arch kernels Dave Martin
2011-08-10 10:13 ` [RFC PATCH 1/5] ARM: Make cpu_alignment into a global variable Dave Martin
2011-08-10 11:38 ` Tixy
2011-08-10 10:13 ` [RFC PATCH 2/5] ARM: s3c24xx: Reference cpu_architecture as " Dave Martin
2011-08-10 10:13 ` [RFC PATCH 3/5] ARM: kprobes: " Dave Martin
2011-08-10 11:43 ` Tixy
2011-08-10 10:13 ` [RFC PATCH 4/5] ARM: entry: Remove unnecessary masking when decoding Thumb-2 instructions Dave Martin
2011-08-10 10:13 ` [RFC PATCH 5/5] ARM: entry: Fix Thumb-2 undef handling for multi-CPU kernels Dave Martin
2011-08-10 11:55 ` Tixy
2011-08-11 13:04 ` Dave Martin
2011-09-01 14:52 ` Arnd Bergmann [this message]
2011-09-07 10:54 ` Dave Martin
2011-09-12 10:33 ` Dave Martin
2011-08-10 11:31 ` [RFC PATCH 0/5] Fix Thumb-2 undef handling for mixed-arch kernels Tixy
2011-08-11 13:10 ` Dave Martin
2011-08-15 23:13 ` Nicolas Pitre
2011-08-16 9:04 ` Dave Martin
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