This is a note to let you know that I've just added the patch titled x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry() to the 5.15-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: x86-entry-move-push_and_clear_regs-out-of-error_entry.patch and it can be found in the queue-5.15 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From foo@baz Tue Jul 12 05:06:57 PM CEST 2022 From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx> Date: Thu, 21 Apr 2022 22:10:50 +0800 Subject: x86/entry: Move PUSH_AND_CLEAR_REGS out of error_entry() From: Lai Jiangshan <jiangshan.ljs@xxxxxxxxxxxx> commit ee774dac0da1543376a69fd90840af6aa86879b3 upstream. 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@xxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Reviewed-by: Juergen Gross <jgross@xxxxxxxx> Link: https://lore.kernel.org/r/20220503032107.680190-4-jiangshanlai@xxxxxxxxx Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- arch/x86/entry/entry_64.S | 15 ++++++++++++--- 1 file changed, 12 insertions(+), 3 deletions(-) --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -315,6 +315,14 @@ 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 @@ -322,6 +330,9 @@ 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 @@ -965,13 +976,11 @@ 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 Patches currently in stable-queue which might be from jiangshan.ljs@xxxxxxxxxxxx are queue-5.15/x86-entry-move-push_and_clear_regs-out-of-error_entry.patch queue-5.15/x86-entry-switch-the-stack-after-error_entry-returns.patch queue-5.15/x86-entry-don-t-call-error_entry-for-xenpv.patch queue-5.15/x86-traps-use-pt_regs-directly-in-fixup_bad_iret.patch