x86/retpoline: Do the necessary fixup to the Zen3/4 srso return thunk for !SRSO
Commit 0e110732 upstream. 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. In addition: ERROR: modpost: "srso_alias_untrain_ret" [arch/x86/kvm/kvm-amd.ko] undefined! make[2]: *** [scripts/Makefile.modpost:145: Module.symvers] Chyba 1 make[1]: *** [/usr/src/linux-6.8.3/Makefile:1873: modpost] Chyba 2 make: *** [Makefile:240: __sub-make] Chyba 2 since !SRSO builds would use the dummy return thunk as reported by petr.pisar@atlas.cz, https://bugzilla.kernel.org/show_bug.cgi?id=218679. 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/ Signed-off-by:
Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by:
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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