linux-kernel - [RFC PATCH 4/6] bpf: Add a bpf program function argument constraint for PMU map

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Date:	Fri, 17 Jul 2015 18:43:34 +0800
From:	kaixu xia <xiakaixu@...wei.com>
To:	<ast@...mgrid.com>, <davem@...emloft.net>, <acme@...nel.org>,
	<mingo@...hat.com>, <a.p.zijlstra@...llo.nl>,
	<masami.hiramatsu.pt@...achi.com>, <jolsa@...nel.org>
CC:	<xiakaixu@...wei.com>, <wangnan0@...wei.com>,
	<linux-kernel@...r.kernel.org>, <pi3orama@....com>,
	<hekuang@...wei.com>
Subject: [RFC PATCH 4/6] bpf: Add a bpf program function argument constraint for PMU map

For the pmu that contains the pointer to struct perf_event,
add the corresponding bpf program function argument constraint
'ARG_PTR_TO_MAP_PERF_EVENT_VALUE'.

Signed-off-by: kaixu xia <xiakaixu@...wei.com>
---
 include/linux/bpf.h   |    1 +
 kernel/bpf/verifier.c |    9 +++++++++
 2 files changed, 10 insertions(+)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f593199..31a93fc 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -56,6 +56,7 @@ enum bpf_arg_type {
 	ARG_CONST_MAP_PTR,	/* const argument used as pointer to bpf_map */
 	ARG_PTR_TO_MAP_KEY,	/* pointer to stack used as map key */
 	ARG_PTR_TO_MAP_VALUE,	/* pointer to stack used as map value */
+	ARG_PTR_TO_MAP_PERF_EVENT_VALUE,	/* pointer to stack used as map pmu value */
 
 	/* the following constraints used to prototype bpf_memcmp() and other
 	 * functions that access data on eBPF program stack
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 039d866..a04223b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -132,6 +132,7 @@ enum bpf_reg_type {
 	PTR_TO_CTX,		 /* reg points to bpf_context */
 	CONST_PTR_TO_MAP,	 /* reg points to struct bpf_map */
 	PTR_TO_MAP_VALUE,	 /* reg points to map element value */
+	PTR_TO_PTR_PERF_EVENT,	 /* reg points to map element pmu value */
 	PTR_TO_MAP_VALUE_OR_NULL,/* points to map elem value or NULL */
 	FRAME_PTR,		 /* reg == frame_pointer */
 	PTR_TO_STACK,		 /* reg == frame_pointer + imm */
@@ -769,6 +770,8 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
 	if (arg_type == ARG_PTR_TO_STACK || arg_type == ARG_PTR_TO_MAP_KEY ||
 	    arg_type == ARG_PTR_TO_MAP_VALUE) {
 		expected_type = PTR_TO_STACK;
+	} else if (arg_type == ARG_PTR_TO_MAP_PERF_EVENT_VALUE) {
+		expected_type = PTR_TO_PTR_PERF_EVENT;
 	} else if (arg_type == ARG_CONST_STACK_SIZE) {
 		expected_type = CONST_IMM;
 	} else if (arg_type == ARG_CONST_MAP_PTR) {
@@ -817,6 +820,9 @@ static int check_func_arg(struct verifier_env *env, u32 regno,
 		}
 		err = check_stack_boundary(env, regno, (*mapp)->value_size);
 
+	} else if (arg_type == ARG_PTR_TO_MAP_PERF_EVENT_VALUE) {
+		/* check for ARG_PTR_TO_MAP_PERF_EVENT_VALUE has been done before*/
+
 	} else if (arg_type == ARG_CONST_STACK_SIZE) {
 		/* bpf_xxx(..., buf, len) call will access 'len' bytes
 		 * from stack pointer 'buf'. Check it
@@ -902,6 +908,9 @@ static int check_call(struct verifier_env *env, int func_id)
 			return -EINVAL;
 		}
 		regs[BPF_REG_0].map_ptr = map;
+
+		if (map->flags & BPF_MAP_FLAG_PERF_EVENT)
+			regs[BPF_REG_0].type = PTR_TO_PTR_PERF_EVENT;
 	} else {
 		verbose("unknown return type %d of func %d\n",
 			fn->ret_type, func_id);
-- 
1.7.10.4

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