lkml.org 
[lkml]   [2022]   [May]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[tip: x86/asm] x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry()
The following commit has been merged into the x86/asm branch of tip:

Commit-ID: ee774dac0da1543376a69fd90840af6aa86879b3
Gitweb: https://git.kernel.org/tip/ee774dac0da1543376a69fd90840af6aa86879b3
Author: Lai Jiangshan <jiangshan.ljs@antgroup.com>
AuthorDate: Thu, 21 Apr 2022 22:10:50 +08:00
Committer: Borislav Petkov <bp@suse.de>
CommitterDate: Tue, 03 May 2022 11:42:59 +02:00

x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry()

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
---
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 ca3e99e..b1cef3b 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

\
 
 \ /
  Last update: 2022-05-03 21:02    [W:0.685 / U:1.120 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site