Messages in this thread Patch in this message | | | Date | Wed, 3 Apr 2024 14:23:50 +0200 | From | Borislav Petkov <> | Subject | [PATCH] x86/retpoline: Fix a missing return thunk warning (was: Re: [linus:master] [x86/bugs] 4535e1a417: WARNING:at_arch/x86/kernel/alternative.c:#apply_returns) |
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On Tue, Apr 02, 2024 at 10:14:07AM +0800, kernel test robot wrote: > > > Hello, > > kernel test robot noticed "WARNING:at_arch/x86/kernel/alternative.c:#apply_returns" on: > > commit: 4535e1a4174c4111d92c5a9a21e542d232e0fcaa ("x86/bugs: Fix the SRSO mitigation on Zen3/4") > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
--- From: "Borislav Petkov (AMD)" <bp@alien8.de> Date: Tue, 2 Apr 2024 16:05:49 +0200 Subject: [PATCH] x86/retpoline: Fix a missing return thunk warning
The srso_alias_untrain_ret() dummy thunk in the !CONFIG_MITIGATION_SRSO case is there only for the altenative in CALL_UNTRAIN_RET to have a symbol to resolve.
However, testing with kernels which don't have CONFIG_MITIGATION_SRSO enabled, leads to the warning in patch_return() to fire:
missing return thunk: srso_alias_untrain_ret+0x0/0x10-0x0: eb 0e 66 66 2e WARNING: CPU: 0 PID: 0 at arch/x86/kernel/alternative.c:826 apply_returns (arch/x86/kernel/alternative.c:826
Put in a plain "ret" there so that gcc doesn't put a return thunk in in its place which special and gets checked.
Reported-by: kernel test robot <oliver.sang@intel.com> Closes: https://lore.kernel.org/oe-lkp/202404020901.da75a60f-oliver.sang@intel.com Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de> Link: https://lore.kernel.org/all/202404020901.da75a60f-oliver.sang@intel.com/ --- arch/x86/lib/retpoline.S | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/arch/x86/lib/retpoline.S b/arch/x86/lib/retpoline.S index 02cde194a99e..440cc58986fa 100644 --- a/arch/x86/lib/retpoline.S +++ b/arch/x86/lib/retpoline.S @@ -228,7 +228,9 @@ SYM_CODE_END(srso_return_thunk) #else /* !CONFIG_MITIGATION_SRSO */ /* Dummy for the alternative in CALL_UNTRAIN_RET. */ SYM_CODE_START(srso_alias_untrain_ret) - RET + ANNOTATE_UNRET_SAFE + ret + int3 SYM_FUNC_END(srso_alias_untrain_ret) #define JMP_SRSO_UNTRAIN_RET "ud2" #endif /* CONFIG_MITIGATION_SRSO */ -- 2.43.0 -- Regards/Gruss, Boris.
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