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x86/ftrace: Use alternative RET encoding

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Upstream commit: 1f001e9da6

Use the return thunk in ftrace trampolines, if needed.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Zijlstra
2022-06-14 23:15:40 +02:00
committed by Greg Kroah-Hartman
parent b9d69bfff6
commit 5ca1f6adac
1 changed files with 5 additions and 2 deletions
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7
arch/x86/kernel/ftrace.c
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@@ -311,7 +311,7 @@ union ftrace_op_code_union {
} __attribute__((packed));
};
#define RET_SIZE 1 + IS_ENABLED(CONFIG_SLS)
#define RET_SIZE (IS_ENABLED(CONFIG_RETPOLINE) ? 5 : 1 + IS_ENABLED(CONFIG_SLS))
static unsigned long
create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
@@ -367,7 +367,10 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
goto fail;
ip = trampoline + size;
memcpy(ip, retq, RET_SIZE);
if (cpu_feature_enabled(X86_FEATURE_RETHUNK))
__text_gen_insn(ip, JMP32_INSN_OPCODE, ip, &__x86_return_thunk, JMP32_INSN_SIZE);
else
memcpy(ip, retq, sizeof(retq));
/* No need to test direct calls on created trampolines */
if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {