[PATCH 16/24] x86/entry: Use skip_rdi instead of save_ret for PUSH_AND_CLEAR_REGS

[Lai Jiangshan <jiangshanlai@gmail.com>]

From: Lai Jiangshan <laijs@linux.alibaba.com>

It allows the user of PUSH_AND_CLEAR_REGS to use its own ways to handle
the return addr.  For example, error_entry() can save it to r12 directly
instead of moving it around and reduce two instructions.

And in later patch, it allows us to move the return addr lower and
add a little more space between pt_regs and the return addr
which consists a new type ist_regs for IST interrupts.

No functional change intended.

Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
---
 arch/x86/entry/calling.h  | 18 +++++-------------
 arch/x86/entry/entry_64.S | 12 ++++++++----
 2 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index 996b041e92d2..aeee1575332f 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -63,15 +63,11 @@ For 32-bit we have the following conventions - kernel is built with
  * for assembly code:
  */
 
-.macro PUSH_REGS rdx=%rdx rax=%rax save_ret=0
-	.if \save_ret
-	pushq	%rsi		/* pt_regs->si */
-	movq	8(%rsp), %rsi	/* temporarily store the return address in %rsi */
-	movq	%rdi, 8(%rsp)	/* pt_regs->di (overwriting original return address) */
-	.else
+.macro PUSH_REGS rdx=%rdx rax=%rax skip_rdi=0
+	.if \skip_rdi == 0
 	pushq   %rdi		/* pt_regs->di */
-	pushq   %rsi		/* pt_regs->si */
 	.endif
+	pushq   %rsi		/* pt_regs->si */
 	pushq	\rdx		/* pt_regs->dx */
 	pushq   %rcx		/* pt_regs->cx */
 	pushq   \rax		/* pt_regs->ax */
@@ -86,10 +82,6 @@ For 32-bit we have the following conventions - kernel is built with
 	pushq	%r14		/* pt_regs->r14 */
 	pushq	%r15		/* pt_regs->r15 */
 	UNWIND_HINT_REGS
-
-	.if \save_ret
-	pushq	%rsi		/* return address on top of stack */
-	.endif
 .endm
 
 .macro CLEAR_REGS
@@ -114,8 +106,8 @@ For 32-bit we have the following conventions - kernel is built with
 
 .endm
 
-.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax save_ret=0
-	PUSH_REGS rdx=\rdx, rax=\rax, save_ret=\save_ret
+.macro PUSH_AND_CLEAR_REGS rdx=%rdx rax=%rax skip_rdi=0
+	PUSH_REGS rdx=\rdx, rax=\rax, skip_rdi=\skip_rdi
 	CLEAR_REGS
 .endm
 
diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index ac67a1109c9c..e968074046c3 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -849,7 +849,10 @@ SYM_CODE_END(xen_failsafe_callback)
 SYM_CODE_START_LOCAL(paranoid_entry)
 	UNWIND_HINT_FUNC
 	cld
-	PUSH_AND_CLEAR_REGS save_ret=1
+	PUSH_AND_CLEAR_REGS skip_rdi=1
+	movq	RDI(%rsp), %rsi	/* temporarily store the return address in %rsi */
+	movq	%rdi, RDI(%rsp) /* put %rdi onto pt_regs */
+	pushq	%rsi		/* put the return address onto the stack */
 	ENCODE_FRAME_POINTER 8
 
 	/*
@@ -973,10 +976,11 @@ SYM_CODE_END(paranoid_exit)
 SYM_CODE_START_LOCAL(error_entry)
 	UNWIND_HINT_FUNC
 	cld
-	PUSH_AND_CLEAR_REGS save_ret=1
-	ENCODE_FRAME_POINTER 8
+	PUSH_AND_CLEAR_REGS skip_rdi=1
+	movq	RDI(%rsp), %r12			/* save return addr in %12 */
+	movq	%rdi, RDI(%rsp)			/* put %rdi onto pt_regs */
+	ENCODE_FRAME_POINTER
 
-	popq	%r12				/* save return addr in %12 */
 	movq	%rsp, %rdi			/* arg0 = pt_regs pointer */
 	call	do_error_entry
 	movq	%rax, %rsp			/* switch stack */
-- 
2.19.1.6.gb485710b