Commit 3c32cc1b authored by Yonghong Song's avatar Yonghong Song Committed by Alexei Starovoitov
Browse files

bpf: Enable bpf_iter targets registering ctx argument types 



Commit b121b341 ("bpf: Add PTR_TO_BTF_ID_OR_NULL
support") adds a field btf_id_or_null_non0_off to
bpf_prog->aux structure to indicate that the
first ctx argument is PTR_TO_BTF_ID reg_type and
all others are PTR_TO_BTF_ID_OR_NULL.
This approach does not really scale if we have
other different reg types in the future, e.g.,
a pointer to a buffer.

This patch enables bpf_iter targets registering ctx argument
reg types which may be different from the default one.
For example, for pointers to structures, the default reg_type
is PTR_TO_BTF_ID for tracing program. The target can register
a particular pointer type as PTR_TO_BTF_ID_OR_NULL which can
be used by the verifier to enforce accesses.

Signed-off-by: default avatarYonghong Song <yhs@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200513180221.2949882-1-yhs@fb.com
parent ab2ee4fc

include/linux/bpf.h

+11 −1
Original line number Diff line number Diff line
@@ -643,6 +643,12 @@ struct bpf_jit_poke_descriptor { 
	u16 reason;

};



/* reg_type info for ctx arguments */

struct bpf_ctx_arg_aux {

	u32 offset;

	enum bpf_reg_type reg_type;

};



struct bpf_prog_aux {

	atomic64_t refcnt;

	u32 used_map_cnt;
@@ -654,12 +660,13 @@ struct bpf_prog_aux { 
	u32 func_cnt; /* used by non-func prog as the number of func progs */

	u32 func_idx; /* 0 for non-func prog, the index in func array for func prog */

	u32 attach_btf_id; /* in-kernel BTF type id to attach to */

	u32 ctx_arg_info_size;

	const struct bpf_ctx_arg_aux *ctx_arg_info;

	struct bpf_prog *linked_prog;

	bool verifier_zext; /* Zero extensions has been inserted by verifier. */

	bool offload_requested;

	bool attach_btf_trace; /* true if attaching to BTF-enabled raw tp */

	bool func_proto_unreliable;

	bool btf_id_or_null_non0_off;

	enum bpf_tramp_prog_type trampoline_prog_type;

	struct bpf_trampoline *trampoline;

	struct hlist_node tramp_hlist;
@@ -1139,12 +1146,15 @@ int bpf_obj_get_user(const char __user *pathname, int flags); 
typedef int (*bpf_iter_init_seq_priv_t)(void *private_data);

typedef void (*bpf_iter_fini_seq_priv_t)(void *private_data);



#define BPF_ITER_CTX_ARG_MAX 2

struct bpf_iter_reg {

	const char *target;

	const struct seq_operations *seq_ops;

	bpf_iter_init_seq_priv_t init_seq_private;

	bpf_iter_fini_seq_priv_t fini_seq_private;

	u32 seq_priv_size;

	u32 ctx_arg_info_size;

	struct bpf_ctx_arg_aux ctx_arg_info[BPF_ITER_CTX_ARG_MAX];

};



struct bpf_iter_meta {

include/net/ip6_fib.h

+7 −0
Original line number Diff line number Diff line
@@ -540,6 +540,13 @@ static inline bool fib6_metric_locked(struct fib6_info *f6i, int metric) 
	return !!(f6i->fib6_metrics->metrics[RTAX_LOCK - 1] & (1 << metric));

}



#if IS_BUILTIN(CONFIG_IPV6) && defined(CONFIG_BPF_SYSCALL)

struct bpf_iter__ipv6_route {

	__bpf_md_ptr(struct bpf_iter_meta *, meta);

	__bpf_md_ptr(struct fib6_info *, rt);

};

#endif



#ifdef CONFIG_IPV6_MULTIPLE_TABLES

static inline bool fib6_has_custom_rules(const struct net *net)

{

kernel/bpf/bpf_iter.c

+5 −0
Original line number Diff line number Diff line
@@ -308,6 +308,11 @@ bool bpf_iter_prog_supported(struct bpf_prog *prog) 
	}

	mutex_unlock(&targets_mutex);



	if (supported) {

		prog->aux->ctx_arg_info_size = tinfo->reg_info->ctx_arg_info_size;

		prog->aux->ctx_arg_info = tinfo->reg_info->ctx_arg_info;

	}



	return supported;

}

kernel/bpf/btf.c

+10 −5
Original line number Diff line number Diff line
@@ -3694,7 +3694,7 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, 
	struct bpf_verifier_log *log = info->log;

	const struct btf_param *args;

	u32 nr_args, arg;

	int ret;

	int i, ret;



	if (off % 8) {

		bpf_log(log, "func '%s' offset %d is not multiple of 8\n",
@@ -3790,10 +3790,15 @@ bool btf_ctx_access(int off, int size, enum bpf_access_type type, 
		return true;



	/* this is a pointer to another type */

	if (off != 0 && prog->aux->btf_id_or_null_non0_off)

		info->reg_type = PTR_TO_BTF_ID_OR_NULL;

	else

	info->reg_type = PTR_TO_BTF_ID;

	for (i = 0; i < prog->aux->ctx_arg_info_size; i++) {

		const struct bpf_ctx_arg_aux *ctx_arg_info = &prog->aux->ctx_arg_info[i];



		if (ctx_arg_info->offset == off) {

			info->reg_type = ctx_arg_info->reg_type;

			break;

		}

	}



	if (tgt_prog) {

		ret = btf_translate_to_vmlinux(log, btf, t, tgt_prog->type, arg);

kernel/bpf/map_iter.c

+5 −0
Original line number Diff line number Diff line
@@ -87,6 +87,11 @@ static const struct bpf_iter_reg bpf_map_reg_info = { 
	.init_seq_private	= NULL,

	.fini_seq_private	= NULL,

	.seq_priv_size		= sizeof(struct bpf_iter_seq_map_info),

	.ctx_arg_info_size	= 1,

	.ctx_arg_info		= {

		{ offsetof(struct bpf_iter__bpf_map, map),

		  PTR_TO_BTF_ID_OR_NULL },

	},

};



static int __init bpf_map_iter_init(void)

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