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x86/ftrace: Use alternative RET encoding

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commit 1f001e9da6bbf482311e45e48f53c2bd2179e59c upstream.

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>
[cascardo: use memcpy(text_gen_insn) as there is no __text_gen_insn]
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Zijlstra 2022-09-14 14:52:38 +03:00 committed by Greg Kroah-Hartman
parent 4586df06a0
commit 35371fd688
1 changed files with 7 additions and 2 deletions
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9
arch/x86/kernel/ftrace.c
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@ -309,7 +309,7 @@ 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)
@ -365,7 +365,12 @@ create_trampoline(struct ftrace_ops *ops, unsigned int *tramp_size)
goto fail;
ip = trampoline + size;
memcpy(ip, retq, RET_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));
/* No need to test direct calls on created trampolines */
if (ops->flags & FTRACE_OPS_FL_SAVE_REGS) {