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Commit 1871853f authored by Frederic Weisbecker's avatar Frederic Weisbecker
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x86,64: Simplify save_regs() 



The save_regs function that saves the regs on low level
irq entry is complicated because of the fact it changes
its stack in the middle and also because it manipulates
data allocated in the caller frame and accesses there
are directly calculated from callee rsp value with the
return address in the middle of the way.

This complicates the static stack offsets calculation and
require more dynamic ones. It also needs a save/restore
of the function's return address.

To simplify and optimize this, turn save_regs() into a
macro.

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jan Beulich <JBeulich@novell.com>
parent 47ce11a2

arch/x86/kernel/entry_64.S

+17 −27
Original line number Diff line number Diff line
@@ -297,27 +297,22 @@ ENDPROC(native_usergs_sysret64) 
	.endm



/* save partial stack frame */

	.pushsection .kprobes.text, "ax"

ENTRY(save_args)

	XCPT_FRAME

	.macro SAVE_ARGS_IRQ

	cld

	/*

	 * start from rbp in pt_regs and jump over

	 * return address.

	 */

	movq_cfi rdi, RDI+8-RBP

	movq_cfi rsi, RSI+8-RBP

	movq_cfi rdx, RDX+8-RBP

	movq_cfi rcx, RCX+8-RBP

	movq_cfi rax, RAX+8-RBP

	movq_cfi  r8,  R8+8-RBP

	movq_cfi  r9,  R9+8-RBP

	movq_cfi r10, R10+8-RBP

	movq_cfi r11, R11+8-RBP



	leaq -RBP+8(%rsp),%rdi	/* arg1 for handler */

	movq_cfi rbp, 8		/* push %rbp */

	leaq 8(%rsp), %rbp		/* mov %rsp, %ebp */

	/* start from rbp in pt_regs and jump over */

	movq_cfi rdi, RDI-RBP

	movq_cfi rsi, RSI-RBP

	movq_cfi rdx, RDX-RBP

	movq_cfi rcx, RCX-RBP

	movq_cfi rax, RAX-RBP

	movq_cfi  r8,  R8-RBP

	movq_cfi  r9,  R9-RBP

	movq_cfi r10, R10-RBP

	movq_cfi r11, R11-RBP



	leaq -RBP(%rsp),%rdi	/* arg1 for handler */

	movq_cfi rbp, 0		/* push %rbp */

	movq %rsp, %rbp

	testl $3, CS(%rdi)

	je 1f

	SWAPGS
@@ -329,19 +324,14 @@ ENTRY(save_args) 
	 */

1:	incl PER_CPU_VAR(irq_count)

	jne 2f

	popq_cfi %rax			/* move return address... */

	mov PER_CPU_VAR(irq_stack_ptr),%rsp

	EMPTY_FRAME 0

	pushq_cfi %rbp			/* backlink for unwinder */

	pushq_cfi %rax			/* ... to the new stack */

	/*

	 * We entered an interrupt context - irqs are off:

	 */

2:	TRACE_IRQS_OFF

	ret

	CFI_ENDPROC

END(save_args)

	.popsection

	.endm



ENTRY(save_rest)

	PARTIAL_FRAME 1 REST_SKIP+8
@@ -791,7 +781,7 @@ END(interrupt) 
	/* reserve pt_regs for scratch regs and rbp */

	subq $ORIG_RAX-RBP, %rsp

	CFI_ADJUST_CFA_OFFSET ORIG_RAX-RBP

	call save_args

	SAVE_ARGS_IRQ

	PARTIAL_FRAME 0

	call \func

	.endm