From: Alexei Starovoitov <ast@kernel.org>
Date: Thu, 14 Nov 2019 10:57:03 -0800
Subject: bpf: Add bpf_arch_text_poke() helper
Patch-mainline: v5.5-rc1
Git-commit: 5964b2000f283ff5df366f718e0f083ebbaae977
References: bsc#1154353
Add bpf_arch_text_poke() helper that is used by BPF trampoline logic to patch
nops/calls in kernel text into calls into BPF trampoline and to patch
calls/nops inside BPF programs too.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20191114185720.1641606-4-ast@kernel.org
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
arch/x86/net/bpf_jit_comp.c | 51 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/bpf.h | 8 ++++++
kernel/bpf/core.c | 6 +++++
3 files changed, 65 insertions(+)
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -9,9 +9,11 @@
#include <linux/filter.h>
#include <linux/if_vlan.h>
#include <linux/bpf.h>
+#include <linux/memory.h>
#include <asm/extable.h>
#include <asm/set_memory.h>
#include <asm/nospec-branch.h>
+#include <asm/text-patching.h>
static u8 *emit_code(u8 *ptr, u32 bytes, unsigned int len)
{
@@ -486,6 +488,55 @@ static int emit_call(u8 **pprog, void *f
return 0;
}
+int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
+ void *old_addr, void *new_addr)
+{
+ u8 old_insn[X86_CALL_SIZE] = {};
+ u8 new_insn[X86_CALL_SIZE] = {};
+ u8 *prog;
+ int ret;
+
+ if (!is_kernel_text((long)ip))
+ /* BPF trampoline in modules is not supported */
+ return -EINVAL;
+
+ if (old_addr) {
+ prog = old_insn;
+ ret = emit_call(&prog, old_addr, (void *)ip);
+ if (ret)
+ return ret;
+ }
+ if (new_addr) {
+ prog = new_insn;
+ ret = emit_call(&prog, new_addr, (void *)ip);
+ if (ret)
+ return ret;
+ }
+ ret = -EBUSY;
+ mutex_lock(&text_mutex);
+ switch (t) {
+ case BPF_MOD_NOP_TO_CALL:
+ if (memcmp(ip, ideal_nops[NOP_ATOMIC5], X86_CALL_SIZE))
+ goto out;
+ text_poke_bp(ip, new_insn, X86_CALL_SIZE, NULL);
+ break;
+ case BPF_MOD_CALL_TO_CALL:
+ if (memcmp(ip, old_insn, X86_CALL_SIZE))
+ goto out;
+ text_poke_bp(ip, new_insn, X86_CALL_SIZE, NULL);
+ break;
+ case BPF_MOD_CALL_TO_NOP:
+ if (memcmp(ip, old_insn, X86_CALL_SIZE))
+ goto out;
+ text_poke_bp(ip, ideal_nops[NOP_ATOMIC5], X86_CALL_SIZE, NULL);
+ break;
+ }
+ ret = 0;
+out:
+ mutex_unlock(&text_mutex);
+ return ret;
+}
+
static bool ex_handler_bpf(const struct exception_table_entry *x,
struct pt_regs *regs, int trapnr,
unsigned long error_code, unsigned long fault_addr)
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1157,4 +1157,12 @@ static inline u32 bpf_xdp_sock_convert_c
}
#endif /* CONFIG_INET */
+enum bpf_text_poke_type {
+ BPF_MOD_NOP_TO_CALL,
+ BPF_MOD_CALL_TO_CALL,
+ BPF_MOD_CALL_TO_NOP,
+};
+int bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
+ void *addr1, void *addr2);
+
#endif /* _LINUX_BPF_H */
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2144,6 +2144,12 @@ int __weak skb_copy_bits(const struct sk
return -EFAULT;
}
+int __weak bpf_arch_text_poke(void *ip, enum bpf_text_poke_type t,
+ void *addr1, void *addr2)
+{
+ return -ENOTSUPP;
+}
+
DEFINE_STATIC_KEY_FALSE(bpf_stats_enabled_key);
EXPORT_SYMBOL(bpf_stats_enabled_key);