[PATCH v12 32/37] x86/entry/calling: Allow PUSH_AND_CLEAR_REGS being used beyond actual entry code

[Xin Li <xin3.li@xxxxxxxxx>]

From: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>

PUSH_AND_CLEAR_REGS could be used besides actual entry code; in that case
%rbp shouldn't be cleared (otherwise the frame pointer is destroyed) and
UNWIND_HINT shouldn't be added.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
---
 arch/x86/entry/calling.h | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h
index f6907627172b..eb57c023d5df 100644
--- a/arch/x86/entry/calling.h
+++ b/arch/x86/entry/calling.h
@@ -65,7 +65,7 @@ For 32-bit we have the following conventions - kernel is 
built with
  * for assembly code:
  */
 
-.macro PUSH_REGS rdx=%rdx rcx=%rcx rax=%rax save_ret=0
+.macro PUSH_REGS rdx=%rdx rcx=%rcx rax=%rax save_ret=0 unwind_hint=1
        .if \save_ret
        pushq   %rsi            /* pt_regs->si */
        movq    8(%rsp), %rsi   /* temporarily store the return address in %rsi 
*/
@@ -87,14 +87,17 @@ For 32-bit we have the following conventions - kernel is 
built with
        pushq   %r13            /* pt_regs->r13 */
        pushq   %r14            /* pt_regs->r14 */
        pushq   %r15            /* pt_regs->r15 */
+
+       .if \unwind_hint
        UNWIND_HINT_REGS
+       .endif
 
        .if \save_ret
        pushq   %rsi            /* return address on top of stack */
        .endif
 .endm
 
-.macro CLEAR_REGS
+.macro CLEAR_REGS clear_bp=1
        /*
         * Sanitize registers of values that a speculation attack might
         * otherwise want to exploit. The lower registers are likely clobbered
@@ -109,7 +112,9 @@ For 32-bit we have the following conventions - kernel is 
built with
        xorl    %r10d, %r10d    /* nospec r10 */
        xorl    %r11d, %r11d    /* nospec r11 */
        xorl    %ebx,  %ebx     /* nospec rbx */
+       .if \clear_bp
        xorl    %ebp,  %ebp     /* nospec rbp */
+       .endif
        xorl    %r12d, %r12d    /* nospec r12 */
        xorl    %r13d, %r13d    /* nospec r13 */
        xorl    %r14d, %r14d    /* nospec r14 */
@@ -117,9 +122,9 @@ For 32-bit we have the following conventions - kernel is 
built with
 
 .endm
 
-.macro PUSH_AND_CLEAR_REGS rdx=%rdx rcx=%rcx rax=%rax save_ret=0
-       PUSH_REGS rdx=\rdx, rcx=\rcx, rax=\rax, save_ret=\save_ret
-       CLEAR_REGS
+.macro PUSH_AND_CLEAR_REGS rdx=%rdx rcx=%rcx rax=%rax save_ret=0 clear_bp=1 
unwind_hint=1
+       PUSH_REGS rdx=\rdx, rcx=\rcx, rax=\rax, save_ret=\save_ret 
unwind_hint=\unwind_hint
+       CLEAR_REGS clear_bp=\clear_bp
 .endm
 
 .macro POP_REGS pop_rdi=1
-- 
2.34.1