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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: still copy return from ftrace_stub]
[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: Ben Hutchings <ben@decadent.org.uk>
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 7723edf5ed
commit 00b136bb62
1 changed files with 5 additions and 2 deletions
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7
arch/x86/kernel/ftrace.c
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@ -308,7 +308,7 @@ 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)
/* The trampoline ends with ret(q) */
retq = (unsigned long)ftrace_stub;
ret = copy_from_kernel_nofault(ip, (void *)retq, RET_SIZE);
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);
if (WARN_ON(ret < 0))
goto fail;