x86/entry/64: Move ENTER_IRQ_STACK from interrupt macro to interrupt_entry (2ba64741) · Commits · 戴 / test

Moving the switch to IRQ stack from the interrupt macro to the helper function requires some trickery: All ENTER_IRQ_STACK really cares about is where the "original" stack -- meaning the GP registers etc. -- is stored. Therefore, we need to offset the stored RSP value by 8 whenever ENTER_IRQ_STACK is called from within a function. In such cases, and after switching to the IRQ stack, we need to push the "original" return address (i.e. the return address from the call to the interrupt entry function) to the IRQ stack. This trickery allows us to carve another .85k from the text size (it would be more except for the additional unwind hints): text data bss dec hex filename 18006 0 0 18006 4656 entry_64.o-orig 17158 0 0 17158 4306 entry_64.o Signed-off-by:

Dominik Brodowski <linux@dominikbrodowski.net> Acked-by:

Thomas Gleixner <tglx@linutronix.de> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: David Woodhouse <dwmw2@infradead.org> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: dan.j.williams@intel.com Link: http://lkml.kernel.org/r/20180220210113.6725-3-linux@dominikbrodowski.net Signed-off-by:

Ingo Molnar <mingo@kernel.org>

arch/x86/entry/entry_64.S

+38 −18

Original line number	Diff line number	Diff line
		@@ -448,9 +448,19 @@ END(irq_entries_start)
		*
		* The invariant is that, if irq_count != -1, then the IRQ stack is in use.
		*/
		.macro ENTER_IRQ_STACK regs=1 old_rsp
		.macro ENTER_IRQ_STACK regs=1 old_rsp save_ret=0
		DEBUG_ENTRY_ASSERT_IRQS_OFF

		.if \save_ret
		/*
		* If save_ret is set, the original stack contains one additional
		* entry -- the return address. Therefore, move the address one
		* entry below %rsp to \old_rsp.
		*/
		leaq 8(%rsp), \old_rsp
		.else
		movq %rsp, \old_rsp
		.endif

		.if \regs
		UNWIND_HINT_REGS base=\old_rsp
		@@ -496,6 +506,15 @@ END(irq_entries_start)
		.if \regs
		UNWIND_HINT_REGS indirect=1
		.endif

		.if \save_ret
		/*
		* Push the return address to the stack. This return address can
		* be found at the "real" original RSP, which was offset by 8 at
		* the beginning of this macro.
		*/
		pushq -8(\old_rsp)
		.endif
		.endm

		/*
		@@ -531,22 +550,7 @@ ENTRY(interrupt_entry)
		PUSH_AND_CLEAR_REGS save_ret=1
		ENCODE_FRAME_POINTER 8

		ret
		END(interrupt_entry)

		/* 0(%rsp): ~(interrupt number) */
		.macro interrupt func
		cld

		testb $3, CS-ORIG_RAX(%rsp)
		jz 1f
		SWAPGS
		call switch_to_thread_stack
		1:

		call interrupt_entry

		testb $3, CS(%rsp)
		testb $3, CS+8(%rsp)
		jz 1f

		/*
		@@ -564,10 +568,26 @@ END(interrupt_entry)
		CALL_enter_from_user_mode

		1:
		ENTER_IRQ_STACK old_rsp=%rdi
		ENTER_IRQ_STACK old_rsp=%rdi save_ret=1
		/* We entered an interrupt context - irqs are off: */
		TRACE_IRQS_OFF

		ret
		END(interrupt_entry)

		/* 0(%rsp): ~(interrupt number) */
		.macro interrupt func
		cld

		testb $3, CS-ORIG_RAX(%rsp)
		jz 1f
		SWAPGS
		call switch_to_thread_stack
		1:

		call interrupt_entry

		UNWIND_HINT_REGS indirect=1
		call \func /* rdi points to pt_regs */
		.endm

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