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Revert "x86/ftrace: Use alternative RET encoding"

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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 <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thadeu Lima de Souza Cascardo 2022-08-16 05:26:56 -03:00 committed by Greg Kroah-Hartman
parent cb69d4d6f7
commit f663276348
1 changed files with 2 additions and 5 deletions
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7
arch/x86/kernel/ftrace.c
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@ -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;