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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 v3 bpf-next 02/18] bpf: Add bpf_arch_text_poke() helper
Date: Thu, 7 Nov 2019 22:40:23 -0800
Message-ID: <20191108064039.2041889-3-ast@kernel.org> (raw)
In-Reply-To: <20191108064039.2041889-1-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>
---
 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


  parent reply index

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-08  6:40 [PATCH v3 bpf-next 00/18] Introduce BPF trampoline Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 01/18] bpf: refactor x86 JIT into helpers Alexei Starovoitov
2019-11-08 19:27   ` Andrii Nakryiko
2019-11-08  6:40 ` Alexei Starovoitov [this message]
2019-11-08  6:56   ` [PATCH v3 bpf-next 02/18] bpf: Add bpf_arch_text_poke() helper Song Liu
2019-11-08  8:23   ` Björn Töpel
2019-11-08 14:09     ` Alexei Starovoitov
2019-11-08  9:11   ` Peter Zijlstra
2019-11-08  9:36     ` Peter Zijlstra
2019-11-08 13:41       ` Alexei Starovoitov
2019-11-08 19:32         ` Alexei Starovoitov
2019-11-08 21:36           ` Peter Zijlstra
2019-11-08 21:39             ` David Miller
2019-11-11  8:14               ` Peter Zijlstra
2019-11-11 10:21                 ` Daniel Borkmann
2019-11-11 16:10                 ` Jonathan Corbet
2019-11-08 23:05             ` Alexei Starovoitov
2019-11-10 10:54               ` Thomas Gleixner
2019-11-08  6:40 ` [PATCH v3 bpf-next 03/18] bpf: Introduce BPF trampoline Alexei Starovoitov
2019-11-08  7:04   ` Song Liu
2019-11-08  6:40 ` [PATCH v3 bpf-next 04/18] libbpf: Introduce btf__find_by_name_kind() Alexei Starovoitov
2019-11-08  7:05   ` Song Liu
2019-11-08 19:21   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 05/18] libbpf: Add support to attach to fentry/fexit tracing progs Alexei Starovoitov
2019-11-08  7:12   ` Song Liu
2019-11-08 19:44   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 06/18] selftest/bpf: Simple test for fentry/fexit Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 07/18] bpf: Add kernel test functions for fentry testing Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 08/18] selftests/bpf: Add test for BPF trampoline Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 09/18] selftests/bpf: Add fexit tests " Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 10/18] selftests/bpf: Add combined fentry/fexit test Alexei Starovoitov
2019-11-08  7:14   ` Song Liu
2019-11-08  6:40 ` [PATCH v3 bpf-next 11/18] selftests/bpf: Add stress test for maximum number of progs Alexei Starovoitov
2019-11-08  7:24   ` Song Liu
2019-11-08  6:40 ` [PATCH v3 bpf-next 12/18] bpf: Reserve space for BPF trampoline in BPF programs Alexei Starovoitov
2019-11-08  7:25   ` Song Liu
2019-11-08  6:40 ` [PATCH v3 bpf-next 13/18] bpf: Fix race in btf_resolve_helper_id() Alexei Starovoitov
2019-11-08  7:32   ` Song Liu
2019-11-08 19:58   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 14/18] bpf: Compare BTF types of functions arguments with actual types Alexei Starovoitov
2019-11-08 17:28   ` Song Liu
2019-11-08 17:32     ` Song Liu
2019-11-08 17:57       ` Alexei Starovoitov
2019-11-08 17:59         ` Song Liu
2019-11-08 23:46   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 15/18] bpf: Support attaching tracing BPF program to other BPF programs Alexei Starovoitov
2019-11-08 18:49   ` Song Liu
2019-11-08 18:59     ` Alexei Starovoitov
2019-11-08 20:17   ` Toke Høiland-Jørgensen
2019-11-08 21:14     ` Alexei Starovoitov
2019-11-08 21:32       ` Toke Høiland-Jørgensen
2019-11-10  7:17   ` Andrii Nakryiko
2019-11-11 23:04     ` Alexei Starovoitov
2019-11-12  4:38       ` Andrii Nakryiko
2019-11-12  4:47         ` Alexei Starovoitov
2019-11-08  6:40 ` [PATCH v3 bpf-next 16/18] libbpf: Add support for attaching BPF programs " Alexei Starovoitov
2019-11-08 18:57   ` Song Liu
2019-11-08 19:13     ` Alexei Starovoitov
2019-11-08 19:14       ` Song Liu
2019-11-10 16:56   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 17/18] selftests/bpf: Extend test_pkt_access test Alexei Starovoitov
2019-11-08 19:03   ` Song Liu
2019-11-10 16:58   ` Andrii Nakryiko
2019-11-08  6:40 ` [PATCH v3 bpf-next 18/18] selftests/bpf: Add a test for attaching BPF prog to another BPF prog and subprog Alexei Starovoitov
2019-11-08 19:13   ` Song Liu
2019-11-10 17:04   ` Andrii Nakryiko
2019-11-11 23:07     ` Alexei Starovoitov

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