[PATCH 5.15 088/245] Revert "x86/ftrace: Use alternative RET encoding"

Greg Kroah-Hartman
2024-02-27T14:05:01Z

From: "Borislav Petkov (AMD)" <bp@alien8.de>

This reverts commit 3eb602ad6a94a76941f93173131a71ad36fa1324.

Revert the backport of upstream commit

1f001e9da6bb ("x86/ftrace: Use alternative RET encoding")

in favor of a proper backport after backporting the commit which adds
__text_gen_insn().

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/kernel/ftrace.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -311,7 +311,7 @@ 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)
@@ -367,12 +367,7 @@ create_trampoline(struct ftrace_ops *ops
goto fail;

ip = trampoline + size;
-
- /* The trampoline ends with ret(q) */
- if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
- memcpy(ip, text_gen_insn(JMP32_INSN_OPCODE, ip, &__x86_return_thunk), JMP32_INSN_SIZE);
- else
- memcpy(ip, retq, sizeof(retq));
+ memcpy(ip, retq, RET_SIZE);

/* No need to test direct calls on created trampolines */
if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {