Commit ccf21861 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by sanglipeng1
Browse files

x86/alternative: Make custom return thunk unconditional 

stable inclusion
from stable-v5.10.211
commit 1dfe6393d17936e285f58d4e35aa14affd153a3b
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IAF2J4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1dfe6393d17936e285f58d4e35aa14affd153a3b



--------------------------------

Upstream commit: 095b8303

There is infrastructure to rewrite return thunks to point to any
random thunk one desires, unwrap that from CALL_THUNKS, which up to
now was the sole user of that.

  [ bp: Make the thunks visible on 32-bit and add ifdeffery for the
    32-bit builds. ]

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230814121148.775293785@infradead.org


Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarsanglipeng1 <sanglipeng1@jd.com>
parent 0a1058b1

arch/x86/include/asm/nospec-branch.h

+4 −4
Original line number Diff line number Diff line
@@ -190,7 +190,11 @@ 
	_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);
@@ -203,11 +207,7 @@ extern void srso_alias_untrain_ret(void); 
extern void entry_untrain_ret(void);

extern void entry_ibpb(void);



#ifdef CONFIG_CALL_THUNKS

extern void (*x86_return_thunk)(void);

#else

#define x86_return_thunk	(&__x86_return_thunk)

#endif



#ifdef CONFIG_RETPOLINE

arch/x86/kernel/alternative.c

+0 −4
Original line number Diff line number Diff line
@@ -521,10 +521,6 @@ void __init_or_module noinline apply_retpolines(s32 *start, s32 *end) 


#ifdef CONFIG_RETHUNK



#ifdef CONFIG_CALL_THUNKS

void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;

#endif



/*

 * Rewrite the compiler generated return thunk tail-calls.

 *

arch/x86/kernel/cpu/bugs.c

+2 −0
Original line number Diff line number Diff line
@@ -61,6 +61,8 @@ EXPORT_SYMBOL_GPL(x86_pred_cmd); 


static DEFINE_MUTEX(spec_ctrl_mutex);



void (*x86_return_thunk)(void) __ro_after_init = &__x86_return_thunk;



/* Update SPEC_CTRL MSR and its cached copy unconditionally */

static void update_spec_ctrl(u64 val)

{