From: Thadeu Lima de Souza Cascardo Date: Tue, 16 Aug 2022 08:26:56 +0000 (-0300) Subject: Revert "x86/ftrace: Use alternative RET encoding" X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=f6632763484c6078f65eff3fd0044cc2bc82fd18;p=linux.git Revert "x86/ftrace: Use alternative RET encoding" This reverts commit e54fcb0812faebd147de72bd37ad87cc4951c68c. This temporarily reverts the backport of upstream commit 1f001e9da6bbf482311e45e48f53c2bd2179e59c. It was not correct to copy the ftrace stub as it would contain a relative jump to the return thunk which would not apply to the context where it was being copied to, leading to ftrace support to be broken. Signed-off-by: Thadeu Lima de Souza Cascardo Signed-off-by: Greg Kroah-Hartman --- diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c index ceab282775461..5080f578236a5 100644 --- a/arch/x86/kernel/ftrace.c +++ b/arch/x86/kernel/ftrace.c @@ -309,7 +309,7 @@ union ftrace_op_code_union { } __attribute__((packed)); }; -#define RET_SIZE (IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS)) +#define RET_SIZE 1 + IS_ENABLED(CONFIG_SLS) static unsigned long create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) @@ -368,10 +368,7 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size) /* The trampoline ends with ret(q) */ retq = (unsigned long)ftrace_stub; - if (cpu_feature_enabled(X86_FEATURE_RETHUNK)) - memcpy(ip, text_gen_insn(JMP32_INSN_OPCODE, ip, &__x86_return_thunk), JMP32_INSN_SIZE); - else - ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE); + ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE); if (WARN_ON(ret < 0)) goto fail;