Messages in this thread Patch in this message | | | Date | Wed, 9 Apr 2014 16:54:16 +0200 | Subject | Re: [PATCH] ARM: reinsert ARCH_MULTI_V4 Kconfig option | From | Jonas Jensen <> |
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On 13 December 2013 12:39, Russell King - ARM Linux <linux@arm.linux.org.uk> wrote: > I see what's causing this: the kuser helpers are using "bx lr" to return > which will be undefined on non-Thumb CPUs. We generally cope fine with > non-Thumb CPUs, conditionalising where necessary on HWCAP_THUMB or the > T bit in the PSR being set. > > However, it looks like the kuser helpers got missed. As a check, please > look at arch/arm/kernel/entry-armv.S, find the line with: > > .macro usr_ret, reg > > and ensure that the mov pc, \reg case always gets used. Please report > back.
Uwe and Arnd came up with a solution except it doesn't work when I test it.
The suggested patch is:
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S index 1879e8d..de15bfd 100644 --- a/arch/arm/kernel/entry-armv.S +++ b/arch/arm/kernel/entry-armv.S @@ -739,6 +739,18 @@ ENDPROC(__switch_to)
.macro usr_ret, reg #ifdef CONFIG_ARM_THUMB + /* + * Having CONFIG_ARM_THUMB isn't a guarantee that the cpu has support + * for Thumb and so the bx instruction. Use a mov if the address to + * jump to is 32 bit aligned. (Note that this code is compiled in ARM + * mode, so this is the right test.) + */ +#if defined(CONFIG_CPU_32v4) + tst \reg, #3 + moveq pc, \reg + b . +#endif + bx \reg #else mov pc, \reg
With this applied, and the following two possibilities in next-20140403:
[1] ARCH_MULTI_V4 only (no CONFIG_ARM_THUMB) CONFIG_CPU_32v4=y
[2] ARCH_MULTI_V4 and ARCH_MULTI_V4T CONFIG_ARM_THUMB=y CONFIG_CPU_32v4=y CONFIG_CPU_32v4T=y
Booting a kernel with either option [1] or [2] yield the following results:
[1] works [2] hangs after "[ 2.730000] Freeing unused kernel memory: 104K (c02f5000 - c030f000)"
Any help why the moveq doesn't work would be much appreciated.
The commit where this was tested: https://bitbucket.org/Kasreyn/linux-next/commits/48320cbe0d5a1fb6ada52cea9efd87c7712367cb
Regards, Jonas
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