git: bea44a836317 - main - kernel: Use external retpoline thunks

The branch main has been updated by emaste:

URL: https://cgit.FreeBSD.org/src/commit/?id=bea44a83631704110de8bbd7693b683c81d4fe55

commit bea44a83631704110de8bbd7693b683c81d4fe55
Author:     Ed Maste <emaste@FreeBSD.org>
AuthorDate: 2018-03-16 02:29:38 +0000
Commit:     Ed Maste <emaste@FreeBSD.org>
CommitDate: 2026-10-23 15:53:05 +0000

    kernel: Use external retpoline thunks
    
    External retpoline thunks for amd64 and i386 were added in commit
    74d971fe1561 ("x86: Add external retpoline thunk").  Use them when
    WITH_KERNEL_RETPOLINE is set.
    
    There should not be any material performance impact -- the call sites
    are identical, and this just replaces (on amd64) compiler-generated
    __llvm_retpoline_r11 functions in each object with our
    __x86_indirect_thunk_r11.
    
    After this change we could implement boot-time patching, replacing
    __x86_indirect_thunk_r11 with just jmp %r11 when retpoline is not
    required.
    
    Note on i386: An i386 build WITH_KERNEL_RETPOLINE was successful, but
    has not been extensively tested.  Clang may use registers other than
    just eax on i386 and so in the future additional thunks beyond the one
    added in 74d971fe1561 could be required for i386.  Patches are welcome
    if this is important to you.
    
    Reviewed by:    kib
    Sponsored by:   The FreeBSD Foundation
---
 sys/conf/kern.mk | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sys/conf/kern.mk b/sys/conf/kern.mk
index 83881cc05b94..35b7a66bab49 100644
--- a/sys/conf/kern.mk
+++ b/sys/conf/kern.mk
@@ -246,7 +246,7 @@ CFLAGS+=	-fstack-protector-strong
 #
 .if defined(COMPILER_FEATURES) && ${COMPILER_FEATURES:Mretpoline} != "" && \
     ${MK_KERNEL_RETPOLINE} != "no"
-CFLAGS+=	-mretpoline
+CFLAGS+=	-mretpoline-external-thunk
 .endif
 
 #