Commit 57c3bb72 authored by Andrey Ignatov's avatar Andrey Ignatov Committed by Alexei Starovoitov
Browse files

bpf: Introduce ARG_PTR_TO_{INT,LONG} arg types 



Currently the way to pass result from BPF helper to BPF program is to
provide memory area defined by pointer and size: func(void *, size_t).

It works great for generic use-case, but for simple types, such as int,
it's overkill and consumes two arguments when it could use just one.

Introduce new argument types ARG_PTR_TO_INT and ARG_PTR_TO_LONG to be
able to pass result from helper to program via pointer to int and long
correspondingly: func(int *) or func(long *).

New argument types are similar to ARG_PTR_TO_MEM with the following
differences:
* they don't require corresponding ARG_CONST_SIZE argument, predefined
  access sizes are used instead (32bit for int, 64bit for long);
* it's possible to use more than one such an argument in a helper;
* provided pointers have to be aligned.

It's easy to introduce similar ARG_PTR_TO_CHAR and ARG_PTR_TO_SHORT
argument types. It's not done due to lack of use-case though.

Signed-off-by: default avatarAndrey Ignatov <rdna@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 9a1027e5

include/linux/bpf.h

+2 −0
Original line number Diff line number Diff line
@@ -202,6 +202,8 @@ enum bpf_arg_type { 
	ARG_ANYTHING,		/* any (initialized) argument is ok */

	ARG_PTR_TO_SPIN_LOCK,	/* pointer to bpf_spin_lock */

	ARG_PTR_TO_SOCK_COMMON,	/* pointer to sock_common */

	ARG_PTR_TO_INT,		/* pointer to int */

	ARG_PTR_TO_LONG,	/* pointer to long */

};



/* type of values returned from helper functions */

kernel/bpf/verifier.c

+29 −0
Original line number Diff line number Diff line
@@ -2462,6 +2462,22 @@ static bool arg_type_is_mem_size(enum bpf_arg_type type) 
	       type == ARG_CONST_SIZE_OR_ZERO;

}



static bool arg_type_is_int_ptr(enum bpf_arg_type type)

{

	return type == ARG_PTR_TO_INT ||

	       type == ARG_PTR_TO_LONG;

}



static int int_ptr_type_to_size(enum bpf_arg_type type)

{

	if (type == ARG_PTR_TO_INT)

		return sizeof(u32);

	else if (type == ARG_PTR_TO_LONG)

		return sizeof(u64);



	return -EINVAL;

}



static int check_func_arg(struct bpf_verifier_env *env, u32 regno,

			  enum bpf_arg_type arg_type,

			  struct bpf_call_arg_meta *meta)
@@ -2554,6 +2570,12 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, 
			 type != expected_type)

			goto err_type;

		meta->raw_mode = arg_type == ARG_PTR_TO_UNINIT_MEM;

	} else if (arg_type_is_int_ptr(arg_type)) {

		expected_type = PTR_TO_STACK;

		if (!type_is_pkt_pointer(type) &&

		    type != PTR_TO_MAP_VALUE &&

		    type != expected_type)

			goto err_type;

	} else {

		verbose(env, "unsupported arg_type %d\n", arg_type);

		return -EFAULT;
@@ -2635,6 +2657,13 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 regno, 
		err = check_helper_mem_access(env, regno - 1,

					      reg->umax_value,

					      zero_size_allowed, meta);

	} else if (arg_type_is_int_ptr(arg_type)) {

		int size = int_ptr_type_to_size(arg_type);



		err = check_helper_mem_access(env, regno, size, false, meta);

		if (err)

			return err;

		err = check_ptr_alignment(env, reg, 0, size, true);

	}



	return err;

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