From: Pawan Gupta Date: Sat, 1 Mar 2025 02:35:43 +0000 (-0800) Subject: x86/speculation: Simplify and make CALL_NOSPEC consistent X-Git-Tag: v6.15-rc1~216^2~86^2~8^2~14 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cfceff8526a426948b53445c02bcb98453c7330d;p=thirdparty%2Fkernel%2Flinux.git x86/speculation: Simplify and make CALL_NOSPEC consistent CALL_NOSPEC macro is used to generate Spectre-v2 mitigation friendly indirect branches. At compile time the macro defaults to indirect branch, and at runtime those can be patched to thunk based mitigations. This approach is opposite of what is done for the rest of the kernel, where the compile time default is to replace indirect calls with retpoline thunk calls. Make CALL_NOSPEC consistent with the rest of the kernel, default to retpoline thunk at compile time when CONFIG_MITIGATION_RETPOLINE is enabled. Signed-off-by: Pawan Gupta Signed-off-by: Ingo Molnar Cc: Andrew Cooper Cc: Peter Zijlstra Link: https://lore.kernel.org/r/20250228-call-nospec-v3-1-96599fed0f33@linux.intel.com --- diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 7e8bf78c03d5d..1e6b915ce9564 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -424,16 +424,11 @@ static inline void call_depth_return_thunk(void) {} * Inline asm uses the %V modifier which is only in newer GCC * which is ensured when CONFIG_MITIGATION_RETPOLINE is defined. */ -# define CALL_NOSPEC \ - ALTERNATIVE_2( \ - ANNOTATE_RETPOLINE_SAFE \ - "call *%[thunk_target]\n", \ - "call __x86_indirect_thunk_%V[thunk_target]\n", \ - X86_FEATURE_RETPOLINE, \ - "lfence;\n" \ - ANNOTATE_RETPOLINE_SAFE \ - "call *%[thunk_target]\n", \ - X86_FEATURE_RETPOLINE_LFENCE) +#ifdef CONFIG_MITIGATION_RETPOLINE +#define CALL_NOSPEC "call __x86_indirect_thunk_%V[thunk_target]\n" +#else +#define CALL_NOSPEC "call *%[thunk_target]\n" +#endif # define THUNK_TARGET(addr) [thunk_target] "r" (addr)