Commit f8049488 authored by Mark Rutland's avatar Mark Rutland Committed by Will Deacon
Browse files

arm64: entry: add a call_on_irq_stack helper 



When handling IRQ/FIQ exceptions the entry assembly may transition from
a task's stack to a CPU's IRQ stack (and IRQ shadow call stack).

In subsequent patches we want to migrate the IRQ/FIQ triage logic to C,
and as we want to perform some actions on the task stack (e.g. EL1
preemption), we need to switch stacks within the C handler. So that we
can do so, this patch adds a helper to call a function on a CPU's IRQ
stack (and shadow stack as appropriate).

Subsequent patches will make use of the new helper function.

Signed-off-by: default avatarMark Rutland <mark.rutland@arm.com>
Acked-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
Acked-by: default avatarMarc Zyngier <maz@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lore.kernel.org/r/20210607094624.34689-7-mark.rutland@arm.com


Signed-off-by: default avatarWill Deacon <will@kernel.org>
parent 101a5b66

arch/arm64/include/asm/exception.h

+2 −0
Original line number Diff line number Diff line
@@ -40,6 +40,8 @@ asmlinkage void el0_error_compat_handler(struct pt_regs *regs); 


asmlinkage void noinstr enter_el1_irq_or_nmi(struct pt_regs *regs);

asmlinkage void noinstr exit_el1_irq_or_nmi(struct pt_regs *regs);

asmlinkage void call_on_irq_stack(struct pt_regs *regs,

				  void (*func)(struct pt_regs *));

asmlinkage void enter_from_user_mode(void);

asmlinkage void exit_to_user_mode(void);

void arm64_enter_nmi(struct pt_regs *regs);

arch/arm64/kernel/entry.S

+36 −0
Original line number Diff line number Diff line
@@ -982,6 +982,42 @@ SYM_CODE_START(ret_from_fork) 
SYM_CODE_END(ret_from_fork)

NOKPROBE(ret_from_fork)



/*

 * void call_on_irq_stack(struct pt_regs *regs,

 * 		          void (*func)(struct pt_regs *));

 *

 * Calls func(regs) using this CPU's irq stack and shadow irq stack.

 */

SYM_FUNC_START(call_on_irq_stack)

#ifdef CONFIG_SHADOW_CALL_STACK

	stp	scs_sp, xzr, [sp, #-16]!

	ldr_this_cpu scs_sp, irq_shadow_call_stack_ptr, x17

#endif

	/* Create a frame record to save our LR and SP (implicit in FP) */

	stp	x29, x30, [sp, #-16]!

	mov	x29, sp



	ldr_this_cpu x16, irq_stack_ptr, x17

	mov	x15, #IRQ_STACK_SIZE

	add	x16, x16, x15



	/* Move to the new stack and call the function there */

	mov	sp, x16

	blr	x1



	/*

	 * Restore the SP from the FP, and restore the FP and LR from the frame

	 * record.

	 */

	mov	sp, x29

	ldp	x29, x30, [sp], #16

#ifdef CONFIG_SHADOW_CALL_STACK

	ldp	scs_sp, xzr, [sp], #16

#endif

	ret

SYM_FUNC_END(call_on_irq_stack)

NOKPROBE(call_on_irq_stack)



#ifdef CONFIG_ARM_SDE_INTERFACE



#include <asm/sdei.h>