This is a note to let you know that I've just added the patch titled
Revert "x86/ftrace: Use alternative RET encoding"
to the 5.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
revert-x86-ftrace-use-alternative-ret-encoding.patch
and it can be found in the queue-5.15 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Fri Aug 19 01:16:51 PM CEST 2022
From: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
Date: Tue, 16 Aug 2022 05:26:56 -0300
Subject: Revert "x86/ftrace: Use alternative RET encoding"
To: stable@xxxxxxxxxxxxxxx
Cc: paul.gortmaker@xxxxxxxxxxxxx, gregkh@xxxxxxxxxxxxxxxxxxx, peterz@xxxxxxxxxxxxx, bp@xxxxxxx, jpoimboe@xxxxxxxxxx, Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
Message-ID: <20220816082658.172387-1-cascardo@xxxxxxxxxxxxx>
From: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/ftrace.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
--- a/arch/x86/kernel/ftrace.c
+++ b/arch/x86/kernel/ftrace.c
@@ -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
/* 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;
Patches currently in stable-queue which might be from cascardo@xxxxxxxxxxxxx are
queue-5.15/x86-ftrace-use-alternative-ret-encoding.patch
queue-5.15/revert-x86-ftrace-use-alternative-ret-encoding.patch
queue-5.15/net_sched-cls_route-disallow-handle-of-0.patch
queue-5.15/x86-ibt-ftrace-make-function-graph-play-nice.patch
