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x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry()

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The macro idtentry() (through idtentry_body()) calls error_entry()
unconditionally even on XENPV. But XENPV needs to only push and clear
regs.

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.

Carve out PUSH_AND_CLEAR_REGS out of error_entry() and into a separate
function and call it before error_entry() in order to avoid calling
error_entry() on XENPV.

It will also allow for error_entry() to be converted to C code that can
use inlined sync_regs() and save a function call.

  [ bp: Massage commit message. ]

Signed-off-by: Lai Jiangshan <jiangshan.ljs@antgroup.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220503032107.680190-4-jiangshanlai@gmail.com
This commit is contained in:
Lai Jiangshan 2022-04-21 22:10:50 +08:00 committed by Borislav Petkov
parent 520a7e80c9
commit ee774dac0d
1 changed files with 12 additions and 3 deletions
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15
arch/x86/entry/entry_64.S
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@ -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