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Subject[PATCH V7 3/6] x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry()
Date
From: Lai Jiangshan <jiangshan.ljs@antgroup.com>

The macro idtentry calls error_entry() unconditionally even on XENPV.
But the code XENPV needs in error_entry() is PUSH_AND_CLEAR_REGS only.

And PUSH_AND_CLEAR_REGS in error_entry() makes the stack not return to
its original place when the function returns, which means it is not
possible to convert it to a C function.

Move PUSH_AND_CLEAR_REGS out of error_entry(), add a function to wrap
PUSH_AND_CLEAR_REGS and call it before error_entry().

It will allow for error_entry() to be not called on XENPV and for
error_entry() to be converted to C code.

Cc: Juergen Gross <jgross@suse.com>
Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
---
arch/x86/entry/entry_64.S | 15 ++++++++++++---
1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S
index ca3e99e08a44..b1cef3b0a7ab 100644
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -318,6 +318,14 @@ SYM_CODE_END(ret_from_fork)
#endif
.endm

+/* Save all registers in pt_regs */
+SYM_CODE_START_LOCAL(push_and_clear_regs)
+ UNWIND_HINT_FUNC
+ PUSH_AND_CLEAR_REGS save_ret=1
+ ENCODE_FRAME_POINTER 8
+ RET
+SYM_CODE_END(push_and_clear_regs)
+
/**
* idtentry_body - Macro to emit code calling the C function
* @cfunc: C function to be called
@@ -325,6 +333,9 @@ SYM_CODE_END(ret_from_fork)
*/
.macro idtentry_body cfunc has_error_code:req

+ call push_and_clear_regs
+ UNWIND_HINT_REGS
+
call error_entry
movq %rax, %rsp /* switch to the task stack if from userspace */
ENCODE_FRAME_POINTER
@@ -985,13 +996,11 @@ SYM_CODE_START_LOCAL(paranoid_exit)
SYM_CODE_END(paranoid_exit)

/*
- * Save all registers in pt_regs, and switch GS if needed.
+ * Switch GS and CR3 if needed.
*/
SYM_CODE_START_LOCAL(error_entry)
UNWIND_HINT_FUNC
cld
- PUSH_AND_CLEAR_REGS save_ret=1
- ENCODE_FRAME_POINTER 8
testb $3, CS+8(%rsp)
jz .Lerror_kernelspace

--
2.19.1.6.gb485710b
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