From: Alexei Starovoitov <ast@kernel.org>
To: <davem@davemloft.net>
Cc: <daniel@iogearbox.net>, <x86@kernel.org>,
<netdev@vger.kernel.org>, <bpf@vger.kernel.org>,
<kernel-team@fb.com>
Subject: [PATCH v4 bpf-next 03/20] bpf: Add bpf_arch_text_poke() helper
Date: Thu, 14 Nov 2019 10:57:03 -0800 [thread overview]
Message-ID: <20191114185720.1641606-4-ast@kernel.org> (raw)
In-Reply-To: <20191114185720.1641606-1-ast@kernel.org>
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>
Acked-by: Song Liu <songliubraving@fb.com>
---
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 fb99d976ad6e..254b2889e881 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)
{
@@ -486,6 +488,55 @@ 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_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)
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
next prev parent reply other threads:[~2019-11-14 18:57 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-14 18:57 [PATCH v4 bpf-next 00/20] Introduce BPF trampoline Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 01/20] x86/alternatives: Teach text_poke_bp() to emulate instructions Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 02/20] bpf: refactor x86 JIT into helpers Alexei Starovoitov
2019-11-14 18:57 ` Alexei Starovoitov [this message]
2019-11-15 22:18 ` [PATCH v4 bpf-next 03/20] bpf: Add bpf_arch_text_poke() helper Andrii Nakryiko
2019-11-14 18:57 ` [PATCH v4 bpf-next 04/20] bpf: Introduce BPF trampoline Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 05/20] libbpf: Introduce btf__find_by_name_kind() Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 06/20] libbpf: Add support to attach to fentry/fexit tracing progs Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 07/20] selftest/bpf: Simple test for fentry/fexit Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 08/20] bpf: Add kernel test functions for fentry testing Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 09/20] selftests/bpf: Add test for BPF trampoline Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 10/20] selftests/bpf: Add fexit tests " Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 11/20] selftests/bpf: Add combined fentry/fexit test Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 12/20] selftests/bpf: Add stress test for maximum number of progs Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 13/20] bpf: Reserve space for BPF trampoline in BPF programs Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 14/20] bpf: Fix race in btf_resolve_helper_id() Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 15/20] bpf: Annotate context types Alexei Starovoitov
2019-11-14 22:55 ` Song Liu
2019-11-14 23:01 ` Alexei Starovoitov
2019-11-14 23:19 ` Song Liu
2019-11-14 23:23 ` Song Liu
2019-11-14 18:57 ` [PATCH v4 bpf-next 16/20] bpf: Compare BTF types of functions arguments with actual types Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 17/20] bpf: Support attaching tracing BPF program to other BPF programs Alexei Starovoitov
2019-11-14 23:30 ` Song Liu
2019-11-14 18:57 ` [PATCH v4 bpf-next 18/20] libbpf: Add support for attaching BPF programs " Alexei Starovoitov
2019-11-14 23:39 ` Song Liu
2019-11-14 18:57 ` [PATCH v4 bpf-next 19/20] selftests/bpf: Extend test_pkt_access test Alexei Starovoitov
2019-11-14 18:57 ` [PATCH v4 bpf-next 20/20] selftests/bpf: Add a test for attaching BPF prog to another BPF prog and subprog Alexei Starovoitov
2019-11-16 0:01 ` [PATCH v4 bpf-next 00/20] Introduce BPF trampoline Daniel Borkmann
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