Re: [PATCH 04/11] Define the virtual space of KASan's shadow region

On Mon, Oct 16, 2017 at 01:14:54PM +0100, Ard Biesheuvel wrote:

On 16 October 2017 at 12:42, Liuwenliang (Lamb) [off-list ref] wrote:

quoted

On 10/16/2017 07:03 PM, Abbott Liu wrote:

quoted

arch/arm/kernel/entry-armv.S:348: Error: selected processor does not support `movw r1,

  #:lower16:((((0xC0000000-0x01000000)>>3)+((0xC0000000-0x01000000)-(1<<29))))' in ARM mode

quoted

arch/arm/kernel/entry-armv.S:348: Error: selected processor does not support `movt r1,

  #:upper16:((((0xC0000000-0x01000000)>>3)+((0xC0000000-0x01000000)-(1<<29))))' in ARM mode

Thanks for building test. This error can be solved by following code:

--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S

@@ -188,8 +188,7 @@ ENDPROC(__und_invalid)
        get_thread_info tsk
        ldr     r0, [tsk, #TI_ADDR_LIMIT]
 #ifdef CONFIG_KASAN
-   movw r1, #:lower16:TASK_SIZE
-   movt r1, #:upper16:TASK_SIZE
+ ldr r1, =TASK_SIZE
 #else
        mov r1, #TASK_SIZE
 #endif

This is unnecessary:

ldr r1, =TASK_SIZE

will be converted to a mov instruction by the assembler if the value
of TASK_SIZE fits its 12-bit immediate field.

It's an 8-bit immediate field for ARM.

What it won't do is expand it to a pair of movw/movt instructions if it
doesn't fit.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>