[PATCH 5.10 088/122] Revert "x86/alternative: Make custom return thunk unconditional"

Greg Kroah-Hartman
2024-02-27T14:29:30Z

From: "Borislav Petkov (AMD)" <bp@alien8.de>

This reverts commit 08f7cfd44f77b2796582bc26164fdef44dd33b6c.

Revert the backport of upstream commit:

095b8303f383 ("x86/alternative: Make custom return thunk unconditional")

in order to backport the full version now that

770ae1b70952 ("x86/returnthunk: Allow different return thunks")

has been backported.

Revert it here so that the build breakage is kept at minimum.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/include/asm/nospec-branch.h | 4 ----
arch/x86/kernel/cpu/bugs.c | 4 ----
2 files changed, 8 deletions(-)

--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -190,11 +190,7 @@
_ASM_PTR " 999b\n\t" \
".popsection\n\t"

-#ifdef CONFIG_RETHUNK
extern void __x86_return_thunk(void);
-#else
-static inline void __x86_return_thunk(void) {}
-#endif

extern void retbleed_return_thunk(void);
extern void srso_return_thunk(void);
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -61,10 +61,6 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd);

static DEFINE_MUTEX(spec_ctrl_mutex);

-#ifdef CONFIG_CALL_THUNKS
-void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;
-#endif
-
/* Update SPEC_CTRL MSR and its cached copy unconditionally */
static void update_spec_ctrl(u64 val)
{