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Message-ID: <20191108064039.2041889-3-ast@kernel.org>
Date: Thu, 7 Nov 2019 22:40:23 -0800
From: Alexei Starovoitov <ast@...nel.org>
To: <davem@...emloft.net>
CC: <daniel@...earbox.net>, <x86@...nel.org>, <netdev@...r.kernel.org>,
<bpf@...r.kernel.org>, <kernel-team@...com>
Subject: [PATCH v3 bpf-next 02/18] bpf: Add bpf_arch_text_poke() helper
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@...nel.org>
---
arch/x86/net/bpf_jit_comp.c | 51 +++++++++++++++++++++++++++++++++++++
include/linux/bpf.h | 8 ++++++
kernel/bpf/core.c | 6 +++++
3 files changed, 65 insertions(+)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 0399b1f83c23..bb8467fd6715 100644
--- 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)
{
@@ -487,6 +489,55 @@ static int emit_call(u8 **pprog, void *func, void *ip)
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(ip, new_insn, X86_CALL_SIZE);
+ break;
+ case BPF_MOD_CALL_TO_CALL:
+ if (memcmp(ip, old_insn, X86_CALL_SIZE))
+ goto out;
+ text_poke(ip, new_insn, X86_CALL_SIZE);
+ break;
+ case BPF_MOD_CALL_TO_NOP:
+ if (memcmp(ip, old_insn, X86_CALL_SIZE))
+ goto out;
+ text_poke(ip, ideal_nops[NOP_ATOMIC5], X86_CALL_SIZE);
+ 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)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 7c7f518811a6..8b90db25348a 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1157,4 +1157,12 @@ static inline u32 bpf_xdp_sock_convert_ctx_access(enum bpf_access_type type,
}
#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 */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index c1fde0303280..c4bcec1014a9 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2140,6 +2140,12 @@ int __weak skb_copy_bits(const struct sk_buff *skb, int offset, void *to,
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);
--
2.23.0
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