This is a note to let you know that I've just added the patch titled
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:
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 01:18:09 PM CEST 2022
From: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
Date: Tue, 16 Aug 2022 05:26:58 -0300
Subject: 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: <20220816082658.172387-3-cascardo@xxxxxxxxxxxxx>
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
commit 1f001e9da6bbf482311e45e48f53c2bd2179e59c upstream.
Use the return thunk in ftrace trampolines, if needed.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
[cascardo: use memcpy(text_gen_insn) as there is no __text_gen_insn]
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kernel/ftrace.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 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 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
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) {
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
