The patchable_function_entry(5) might output 5 single nop
instructions (depends on toolchain), which will clash with
bpf_arch_text_poke check for 5 bytes nop instruction.
Adding early init call for dispatcher that checks and change
the patchable entry into expected 5 nop instruction if needed.
There's no need to take text_mutex, because we are using it
in early init call which is called at pre-smp time.
Fixes: ceea991a019c ("bpf: Move bpf_dispatcher function out of ftrace locations")
Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
---
arch/x86/net/bpf_jit_comp.c | 13 +++++++++++++
include/linux/bpf.h | 14 +++++++++++++-
kernel/bpf/dispatcher.c | 6 ++++++
3 files changed, 32 insertions(+), 1 deletion(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 0abd082786e7..51afd6d0c05f 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -11,6 +11,7 @@
#include <linux/bpf.h>
#include <linux/memory.h>
#include <linux/sort.h>
+#include <linux/init.h>
#include <asm/extable.h>
#include <asm/set_memory.h>
#include <asm/nospec-branch.h>
@@ -388,6 +389,18 @@ static int __bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
return ret;
}
+int __init bpf_arch_init_dispatcher_early(void *ip)
+{
+ const u8 *nop_insn = x86_nops[5];
+
+ if (is_endbr(*(u32 *)ip))
+ ip += ENDBR_INSN_SIZE;
+
+ if (memcmp(ip, nop_insn, X86_PATCH_SIZE))
+ text_poke_early(ip, nop_insn, X86_PATCH_SIZE);
+ return 0;
+}
+
int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
void *old_addr, void *new_addr)
{
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 9e7d46d16032..0566705c1d4e 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -27,6 +27,7 @@
#include <linux/bpfptr.h>
#include <linux/btf.h>
#include <linux/rcupdate_trace.h>
+#include <linux/init.h>
struct bpf_verifier_env;
struct bpf_verifier_log;
@@ -970,6 +971,8 @@ struct bpf_trampoline *bpf_trampoline_get(u64 key,
struct bpf_attach_target_info *tgt_info);
void bpf_trampoline_put(struct bpf_trampoline *tr);
int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_funcs);
+int __init bpf_arch_init_dispatcher_early(void *ip);
+
#define BPF_DISPATCHER_INIT(_name) { \
.mutex = __MUTEX_INITIALIZER(_name.mutex), \
.func = &_name##_func, \
@@ -983,6 +986,13 @@ int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_func
}, \
}
+#define BPF_DISPATCHER_INIT_CALL(_name) \
+ static int __init _name##_init(void) \
+ { \
+ return bpf_arch_init_dispatcher_early(_name##_func); \
+ } \
+ early_initcall(_name##_init)
+
#ifdef CONFIG_X86_64
#define BPF_DISPATCHER_ATTRIBUTES __attribute__((patchable_function_entry(5)))
#else
@@ -1000,7 +1010,9 @@ int arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int num_func
} \
EXPORT_SYMBOL(bpf_dispatcher_##name##_func); \
struct bpf_dispatcher bpf_dispatcher_##name = \
- BPF_DISPATCHER_INIT(bpf_dispatcher_##name);
+ BPF_DISPATCHER_INIT(bpf_dispatcher_##name); \
+ BPF_DISPATCHER_INIT_CALL(bpf_dispatcher_##name);
+
#define DECLARE_BPF_DISPATCHER(name) \
unsigned int bpf_dispatcher_##name##_func( \
const void *ctx, \
diff --git a/kernel/bpf/dispatcher.c b/kernel/bpf/dispatcher.c
index fa64b80b8bca..04f0a045dcaa 100644
--- a/kernel/bpf/dispatcher.c
+++ b/kernel/bpf/dispatcher.c
@@ -4,6 +4,7 @@
#include <linux/hash.h>
#include <linux/bpf.h>
#include <linux/filter.h>
+#include <linux/init.h>
/* The BPF dispatcher is a multiway branch code generator. The
* dispatcher is a mechanism to avoid the performance penalty of an
@@ -90,6 +91,11 @@ int __weak arch_prepare_bpf_dispatcher(void *image, void *buf, s64 *funcs, int n
return -ENOTSUPP;
}
+int __weak __init bpf_arch_init_dispatcher_early(void *ip)
+{
+ return -ENOTSUPP;
+}
+
static int bpf_dispatcher_prepare(struct bpf_dispatcher *d, void *image, void *buf)
{
s64 ips[BPF_DISPATCHER_MAX] = {}, *ipsp = &ips[0];
--
2.37.3
