On Sun, Aug 18, 2019 at 06:55:51AM +0200, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 4.19-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
> thanks,
>
> greg k-h
Backport to 4.19 below. Thanks,
Will
--->8
>From db621425c314916815fd9a25d4d1213f80b7f2ef Mon Sep 17 00:00:00 2001
From: Will Deacon <will@xxxxxxxxxx>
Date: Fri, 16 Aug 2019 14:57:43 +0100
Subject: [PATCH] arm64: ftrace: Ensure module ftrace trampoline is coherent
with I-side
commit b6143d10d23ebb4a77af311e8b8b7f019d0163e6 upstream.
The initial support for dynamic ftrace trampolines in modules made use
of an indirect branch which loaded its target from the beginning of
a special section (e71a4e1bebaf7 ("arm64: ftrace: add support for far
branches to dynamic ftrace")). Since no instructions were being patched,
no cache maintenance was needed. However, later in be0f272bfc83 ("arm64:
ftrace: emit ftrace-mod.o contents through code") this code was reworked
to output the trampoline instructions directly into the PLT entry but,
unfortunately, the necessary cache maintenance was overlooked.
Add a call to __flush_icache_range() after writing the new trampoline
instructions but before patching in the branch to the trampoline.
Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Cc: James Morse <james.morse@xxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # 4.19.y only
Fixes: be0f272bfc83 ("arm64: ftrace: emit ftrace-mod.o contents through code")
Signed-off-by: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
---
arch/arm64/kernel/ftrace.c | 21 ++++++++++++---------
1 file changed, 12 insertions(+), 9 deletions(-)
diff --git a/arch/arm64/kernel/ftrace.c b/arch/arm64/kernel/ftrace.c
index 57e962290df3..7eff8afa035f 100644
--- a/arch/arm64/kernel/ftrace.c
+++ b/arch/arm64/kernel/ftrace.c
@@ -76,7 +76,7 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
if (offset < -SZ_128M || offset >= SZ_128M) {
#ifdef CONFIG_ARM64_MODULE_PLTS
- struct plt_entry trampoline;
+ struct plt_entry trampoline, *dst;
struct module *mod;
/*
@@ -104,24 +104,27 @@ int ftrace_make_call(struct dyn_ftrace *rec, unsigned long addr)
* is added in the future, but for now, the pr_err() below
* deals with a theoretical issue only.
*/
+ dst = mod->arch.ftrace_trampoline;
trampoline = get_plt_entry(addr);
- if (!plt_entries_equal(mod->arch.ftrace_trampoline,
- &trampoline)) {
- if (!plt_entries_equal(mod->arch.ftrace_trampoline,
- &(struct plt_entry){})) {
+ if (!plt_entries_equal(dst, &trampoline)) {
+ if (!plt_entries_equal(dst, &(struct plt_entry){})) {
pr_err("ftrace: far branches to multiple entry points unsupported inside a single module\n");
return -EINVAL;
}
/* point the trampoline to our ftrace entry point */
module_disable_ro(mod);
- *mod->arch.ftrace_trampoline = trampoline;
+ *dst = trampoline;
module_enable_ro(mod, true);
- /* update trampoline before patching in the branch */
- smp_wmb();
+ /*
+ * Ensure updated trampoline is visible to instruction
+ * fetch before we patch in the branch.
+ */
+ __flush_icache_range((unsigned long)&dst[0],
+ (unsigned long)&dst[1]);
}
- addr = (unsigned long)(void *)mod->arch.ftrace_trampoline;
+ addr = (unsigned long)dst;
#else /* CONFIG_ARM64_MODULE_PLTS */
return -EINVAL;
#endif /* CONFIG_ARM64_MODULE_PLTS */
--
2.11.0
