[PATCHv6 1/8] arm64: Treat handle_arch_irq as a function pointer

[lauraa@codeaurora.org (Laura Abbott)]

handle_arch_irq isn't actually text, it's just a function pointer.
It doesn't need to be stored in the text section and doing so
causes problesm if we ever want to make the kernel text read only.
Declare handle_arch_irq as a proper function pointer stored in
the data section.

Reviewed-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Tested-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>
---
 arch/arm64/include/asm/irq.h | 1 -
 arch/arm64/kernel/entry.S    | 6 ++----
 arch/arm64/kernel/irq.c      | 2 ++
 3 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/irq.h b/arch/arm64/include/asm/irq.h
index e1f7ecd..1eebf5b 100644
--- a/arch/arm64/include/asm/irq.h
+++ b/arch/arm64/include/asm/irq.h
@@ -3,7 +3,6 @@
 
 #include <asm-generic/irq.h>
 
-extern void (*handle_arch_irq)(struct pt_regs *);
 extern void migrate_irqs(void);
 extern void set_handle_irq(void (*handle_irq)(struct pt_regs *));
 
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 726b910..ee27f39 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -168,7 +168,8 @@ tsk	.req	x28		// current thread_info
  * Interrupt handling.
  */
 	.macro	irq_handler
-	ldr	x1, handle_arch_irq
+	adrp	x1, handle_arch_irq
+	ldr	x1, [x1, #:lo12:handle_arch_irq]
 	mov	x0, sp
 	blr	x1
 	.endm
@@ -695,6 +696,3 @@ ENTRY(sys_rt_sigreturn_wrapper)
 	mov	x0, sp
 	b	sys_rt_sigreturn
 ENDPROC(sys_rt_sigreturn_wrapper)
-
-ENTRY(handle_arch_irq)
-	.quad	0
diff --git a/arch/arm64/kernel/irq.c b/arch/arm64/kernel/irq.c
index 071a6ec..240b75c 100644
--- a/arch/arm64/kernel/irq.c
+++ b/arch/arm64/kernel/irq.c
@@ -40,6 +40,8 @@ int arch_show_interrupts(struct seq_file *p, int prec)
 	return 0;
 }
 
+void (*handle_arch_irq)(struct pt_regs *) = NULL;
+
 void __init set_handle_irq(void (*handle_irq)(struct pt_regs *))
 {
 	if (handle_arch_irq)
-- 
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