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Revert "x86/ftrace: Use alternative RET encoding"

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This reverts commit 00b136bb62.

This temporarily reverts the backport of upstream commit
1f001e9da6. 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: Ovidiu Panait <ovidiu.panait@windriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Thadeu Lima de Souza Cascardo 2022-09-14 14:52:36 +03:00 committed by Greg Kroah-Hartman
parent 891f03f688
commit 33015556a9
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;