From: Lai Jiangshan jiangshan.ljs@antgroup.com
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@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 Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@canonical.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- 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 @@ -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 @@ -986,13 +997,11 @@ 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