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Commit ffa47aa6 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Kees Cook
Browse files

ARM: Prepare for randomized task_struct 



With the new task struct randomization, we can run into a build
failure for certain random seeds, which will place fields beyond
the allow immediate size in the assembly:

arch/arm/kernel/entry-armv.S: Assembler messages:
arch/arm/kernel/entry-armv.S:803: Error: bad immediate value for offset (4096)

Only two constants in asm-offset.h are affected, and I'm changing
both of them here to work correctly in all configurations.

One more macro has the problem, but is currently unused, so this
removes it instead of adding complexity.

Suggested-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
[kees: Adjust commit log slightly]
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
parent 1854c19c

arch/arm/include/asm/assembler.h

+2 −0
Original line number Diff line number Diff line
@@ -87,6 +87,8 @@ 
#define CALGN(code...)

#endif



#define IMM12_MASK 0xfff



/*

 * Enable and disable interrupts

 */

arch/arm/kernel/entry-armv.S

+4 −1
Original line number Diff line number Diff line
@@ -797,7 +797,10 @@ ENTRY(__switch_to) 
#if defined(CONFIG_CC_STACKPROTECTOR) && !defined(CONFIG_SMP)

	ldr	r7, [r2, #TI_TASK]

	ldr	r8, =__stack_chk_guard

	ldr	r7, [r7, #TSK_STACK_CANARY]

	.if (TSK_STACK_CANARY > IMM12_MASK)

	add	r7, r7, #TSK_STACK_CANARY & ~IMM12_MASK

	.endif

	ldr	r7, [r7, #TSK_STACK_CANARY & IMM12_MASK]

#endif

#ifdef CONFIG_CPU_USE_DOMAINS

	mcr	p15, 0, r6, c3, c0, 0		@ Set domain register

arch/arm/mm/proc-macros.S

+4 −6
Original line number Diff line number Diff line
@@ -25,11 +25,6 @@ 
	ldr	\rd, [\rn, #VMA_VM_FLAGS]

	.endm



	.macro	tsk_mm, rd, rn

	ldr	\rd, [\rn, #TI_TASK]

	ldr	\rd, [\rd, #TSK_ACTIVE_MM]

	.endm



/*

 * act_mm - get current->active_mm

 */
@@ -37,7 +32,10 @@ 
	bic	\rd, sp, #8128

	bic	\rd, \rd, #63

	ldr	\rd, [\rd, #TI_TASK]

	ldr	\rd, [\rd, #TSK_ACTIVE_MM]

	.if (TSK_ACTIVE_MM > IMM12_MASK)

	add	\rd, \rd, #TSK_ACTIVE_MM & ~IMM12_MASK

	.endif

	ldr	\rd, [\rd, #TSK_ACTIVE_MM & IMM12_MASK]

	.endm



/*