[RFC PATCH 1/6] ARM: entry: preserve thread_info pointer in switch_to
From: Ard Biesheuvel <ardb@kernel.org>
Date: 2021-11-26 10:12:31
Subsystem:
arm port, the rest · Maintainers:
Russell King, Linus Torvalds
Tweak the UP stack protector handling code so that the thread info pointer is preserved in R7 until set_current is called. This is needed for a subsequent patch that implements THREAD_INFO_IN_TASK and set_current for UP as well. This also means we will prefer the per-task protector on UP systems that implement the thread ID registers, so tweak the preprocessor conditionals to reflect this. Signed-off-by: Ard Biesheuvel <ardb@kernel.org> --- arch/arm/kernel/entry-armv.S | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/arch/arm/kernel/entry-armv.S b/arch/arm/kernel/entry-armv.S
index 5fb7465d14d9..1e26d69ebbf1 100644
--- a/arch/arm/kernel/entry-armv.S
+++ b/arch/arm/kernel/entry-armv.S@@ -814,16 +814,16 @@ ENTRY(__switch_to) ldr r6, [r2, #TI_CPU_DOMAIN] #endif switch_tls r1, r4, r5, r3, r7 -#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP) - ldr r7, [r2, #TI_TASK] +#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP) && \ + !defined(CONFIG_STACKPROTECTOR_PER_TASK) + ldr r9, [r2, #TI_TASK] ldr r8, =__stack_chk_guard .if (TSK_STACK_CANARY > IMM12_MASK) - add r7, r7, #TSK_STACK_CANARY & ~IMM12_MASK + add r9, r9, #TSK_STACK_CANARY & ~IMM12_MASK .endif - ldr r7, [r7, #TSK_STACK_CANARY & IMM12_MASK] -#elif defined(CONFIG_CURRENT_POINTER_IN_TPIDRURO) - mov r7, r2 @ Preserve 'next' + ldr r9, [r9, #TSK_STACK_CANARY & IMM12_MASK] #endif + mov r7, r2 @ Preserve 'next' #ifdef CONFIG_CPU_USE_DOMAINS mcr p15, 0, r6, c3, c0, 0 @ Set domain register #endif
@@ -832,8 +832,9 @@ ENTRY(__switch_to) ldr r0, =thread_notify_head mov r1, #THREAD_NOTIFY_SWITCH bl atomic_notifier_call_chain -#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP) - str r7, [r8] +#if defined(CONFIG_STACKPROTECTOR) && !defined(CONFIG_SMP) && \ + !defined(CONFIG_STACKPROTECTOR_PER_TASK) + str r9, [r8] #endif mov r0, r5 #if !defined(CONFIG_THUMB2_KERNEL) && !defined(CONFIG_VMAP_STACK)
--
2.30.2
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