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 08/11] bpf: add support for BTF pointers to interpreter
Date: Tue, 15 Oct 2019 20:25:02 -0700 [thread overview]
Message-ID: <20191016032505.2089704-9-ast@kernel.org> (raw)
In-Reply-To: <20191016032505.2089704-1-ast@kernel.org>
Pointer to BTF object is a pointer to kernel object or NULL.
The memory access in the interpreter has to be done via probe_kernel_read
to avoid page faults.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
---
include/linux/filter.h | 3 +++
kernel/bpf/core.c | 19 +++++++++++++++++++
kernel/bpf/verifier.c | 8 ++++++++
3 files changed, 30 insertions(+)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index d3d51d7aff2c..22ebea2e64ea 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -65,6 +65,9 @@ struct ctl_table_header;
/* unused opcode to mark special call to bpf_tail_call() helper */
#define BPF_TAIL_CALL 0xf0
+/* unused opcode to mark special load instruction. Same as BPF_ABS */
+#define BPF_PROBE_MEM 0x20
+
/* unused opcode to mark call to interpreter with arguments */
#define BPF_CALL_ARGS 0xe0
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 66088a9e9b9e..8a765bbd33f0 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1291,6 +1291,11 @@ bool bpf_opcode_in_insntable(u8 code)
}
#ifndef CONFIG_BPF_JIT_ALWAYS_ON
+u64 __weak bpf_probe_read(void * dst, u32 size, const void * unsafe_ptr)
+{
+ memset(dst, 0, size);
+ return -EFAULT;
+}
/**
* __bpf_prog_run - run eBPF program on a given context
* @regs: is the array of MAX_BPF_EXT_REG eBPF pseudo-registers
@@ -1310,6 +1315,10 @@ static u64 __no_fgcse ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u6
/* Non-UAPI available opcodes. */
[BPF_JMP | BPF_CALL_ARGS] = &&JMP_CALL_ARGS,
[BPF_JMP | BPF_TAIL_CALL] = &&JMP_TAIL_CALL,
+ [BPF_LDX | BPF_PROBE_MEM | BPF_B] = &&LDX_PROBE_MEM_B,
+ [BPF_LDX | BPF_PROBE_MEM | BPF_H] = &&LDX_PROBE_MEM_H,
+ [BPF_LDX | BPF_PROBE_MEM | BPF_W] = &&LDX_PROBE_MEM_W,
+ [BPF_LDX | BPF_PROBE_MEM | BPF_DW] = &&LDX_PROBE_MEM_DW,
};
#undef BPF_INSN_3_LBL
#undef BPF_INSN_2_LBL
@@ -1542,6 +1551,16 @@ static u64 __no_fgcse ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn, u6
LDST(W, u32)
LDST(DW, u64)
#undef LDST
+#define LDX_PROBE(SIZEOP, SIZE) \
+ LDX_PROBE_MEM_##SIZEOP: \
+ bpf_probe_read(&DST, SIZE, (const void *)(long) SRC); \
+ CONT;
+ LDX_PROBE(B, 1)
+ LDX_PROBE(H, 2)
+ LDX_PROBE(W, 4)
+ LDX_PROBE(DW, 8)
+#undef LDX_PROBE
+
STX_XADD_W: /* lock xadd *(u32 *)(dst_reg + off16) += src_reg */
atomic_add((u32) SRC, (atomic_t *)(unsigned long)
(DST + insn->off));
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 42a463e09761..c4b6a2cfcd47 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7581,6 +7581,7 @@ static bool reg_type_mismatch_ok(enum bpf_reg_type type)
case PTR_TO_TCP_SOCK:
case PTR_TO_TCP_SOCK_OR_NULL:
case PTR_TO_XDP_SOCK:
+ case PTR_TO_BTF_ID:
return false;
default:
return true;
@@ -8722,6 +8723,13 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
case PTR_TO_XDP_SOCK:
convert_ctx_access = bpf_xdp_sock_convert_ctx_access;
break;
+ case PTR_TO_BTF_ID:
+ if (type == BPF_WRITE) {
+ verbose(env, "Writes through BTF pointers are not allowed\n");
+ return -EINVAL;
+ }
+ insn->code = BPF_LDX | BPF_PROBE_MEM | BPF_SIZE((insn)->code);
+ continue;
default:
continue;
}
--
2.17.1
next prev parent reply other threads:[~2019-10-16 3:26 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-16 3:24 [PATCH v3 bpf-next 00/11] bpf: revolutionize bpf tracing Alexei Starovoitov
2019-10-16 3:24 ` [PATCH v3 bpf-next 01/11] bpf: add typecast to raw_tracepoints to help BTF generation Alexei Starovoitov
2019-10-16 3:24 ` [PATCH v3 bpf-next 02/11] bpf: add typecast to bpf helpers " Alexei Starovoitov
2019-10-16 3:24 ` [PATCH v3 bpf-next 03/11] bpf: process in-kernel BTF Alexei Starovoitov
2019-10-16 3:24 ` [PATCH v3 bpf-next 04/11] bpf: add attach_btf_id attribute to program load Alexei Starovoitov
2019-10-16 19:45 ` Andrii Nakryiko
2019-10-16 19:50 ` Alexei Starovoitov
2019-10-16 3:24 ` [PATCH v3 bpf-next 05/11] libbpf: auto-detect btf_id of BTF-based raw_tracepoints Alexei Starovoitov
2019-10-16 19:49 ` Andrii Nakryiko
2019-10-16 3:25 ` [PATCH v3 bpf-next 06/11] bpf: implement accurate raw_tp context access via BTF Alexei Starovoitov
2019-10-16 20:09 ` Andrii Nakryiko
2019-10-16 21:21 ` Daniel Borkmann
2019-10-16 21:28 ` Alexei Starovoitov
2019-10-16 22:08 ` Daniel Borkmann
2019-10-16 23:52 ` Alexei Starovoitov
2019-10-16 3:25 ` [PATCH v3 bpf-next 07/11] bpf: attach raw_tp program with BTF via type name Alexei Starovoitov
2019-10-16 20:13 ` Andrii Nakryiko
2019-10-16 3:25 ` Alexei Starovoitov [this message]
2019-10-16 3:25 ` [PATCH v3 bpf-next 09/11] bpf: add support for BTF pointers to x86 JIT Alexei Starovoitov
2019-10-16 20:15 ` Andrii Nakryiko
2019-10-16 3:25 ` [PATCH v3 bpf-next 10/11] bpf: check types of arguments passed into helpers Alexei Starovoitov
2019-10-16 3:25 ` [PATCH v3 bpf-next 11/11] selftests/bpf: add kfree_skb raw_tp test Alexei Starovoitov
2019-10-16 18:01 ` [PATCH v3 bpf-next 00/11] bpf: revolutionize bpf tracing Martin Lau
2019-10-17 15:14 ` Daniel Borkmann
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