Commit 30743837 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

net: filter: make register naming more comprehensible 



The current code is a bit hard to parse on which registers can be used,
how they are mapped and all play together. It makes much more sense to
define this a bit more clearly so that the code is a bit more intuitive.
This patch cleans this up, and makes naming a bit more consistent among
the code. This also allows for moving some of the defines into the header
file. Clearing of A and X registers in __sk_run_filter() do not get a
particular register name assigned as they have not an 'official' function,
but rather just result from the concrete initial mapping of old BPF
programs. Since for BPF helper functions for BPF_CALL we already use
small letters, so be consistent here as well. No functional changes.

Signed-off-by: default avatarDaniel Borkmann <dborkman@redhat.com>
Acked-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 5bcfedf0

include/linux/filter.h

+36 −8
Original line number Diff line number Diff line
@@ -40,16 +40,47 @@ 
/* Placeholder/dummy for 0 */

#define BPF_0		0



/* Register numbers */

enum {

	BPF_REG_0 = 0,

	BPF_REG_1,

	BPF_REG_2,

	BPF_REG_3,

	BPF_REG_4,

	BPF_REG_5,

	BPF_REG_6,

	BPF_REG_7,

	BPF_REG_8,

	BPF_REG_9,

	BPF_REG_10,

	__MAX_BPF_REG,

};



/* BPF has 10 general purpose 64-bit registers and stack frame. */

#define MAX_BPF_REG	11

#define MAX_BPF_REG	__MAX_BPF_REG



/* ArgX, context and stack frame pointer register positions. Note,

 * Arg1, Arg2, Arg3, etc are used as argument mappings of function

 * calls in BPF_CALL instruction.

 */

#define BPF_REG_ARG1	BPF_REG_1

#define BPF_REG_ARG2	BPF_REG_2

#define BPF_REG_ARG3	BPF_REG_3

#define BPF_REG_ARG4	BPF_REG_4

#define BPF_REG_ARG5	BPF_REG_5

#define BPF_REG_CTX	BPF_REG_6

#define BPF_REG_FP	BPF_REG_10



/* Additional register mappings for converted user programs. */

#define BPF_REG_A	BPF_REG_0

#define BPF_REG_X	BPF_REG_7

#define BPF_REG_TMP	BPF_REG_8



/* BPF program can access up to 512 bytes of stack space. */

#define MAX_BPF_STACK	512



/* Arg1, context and stack frame pointer register positions. */

#define ARG1_REG	1

#define CTX_REG		6

#define FP_REG		10

/* Macro to invoke filter function. */

#define SK_RUN_FILTER(filter, ctx)  (*filter->bpf_func)(ctx, filter->insnsi)



struct sock_filter_int {

	__u8	code;		/* opcode */
@@ -100,9 +131,6 @@ static inline unsigned int sk_filter_size(unsigned int proglen) 
#define sk_filter_proglen(fprog)			\

		(fprog->len * sizeof(fprog->filter[0]))



#define SK_RUN_FILTER(filter, ctx)			\

		(*filter->bpf_func)(ctx, filter->insnsi)



int sk_filter(struct sock *sk, struct sk_buff *skb);



u32 sk_run_filter_int_seccomp(const struct seccomp_data *ctx,

net/core/filter.c

+109 −106
Original line number Diff line number Diff line
@@ -45,6 +45,27 @@ 
#include <linux/seccomp.h>

#include <linux/if_vlan.h>



/* Registers */

#define R0	regs[BPF_REG_0]

#define R1	regs[BPF_REG_1]

#define R2	regs[BPF_REG_2]

#define R3	regs[BPF_REG_3]

#define R4	regs[BPF_REG_4]

#define R5	regs[BPF_REG_5]

#define R6	regs[BPF_REG_6]

#define R7	regs[BPF_REG_7]

#define R8	regs[BPF_REG_8]

#define R9	regs[BPF_REG_9]

#define R10	regs[BPF_REG_10]



/* Named registers */

#define A	regs[insn->a_reg]

#define X	regs[insn->x_reg]

#define FP	regs[BPF_REG_FP]

#define ARG1	regs[BPF_REG_ARG1]

#define CTX	regs[BPF_REG_CTX]

#define K	insn->imm



/* No hurry in this branch

 *

 * Exported for the bpf jit load helper.
@@ -122,13 +143,6 @@ noinline u64 __bpf_call_base(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5) 
	return 0;

}



/* Register mappings for user programs. */

#define A_REG		0

#define X_REG		7

#define TMP_REG		8

#define ARG2_REG	2

#define ARG3_REG	3



/**

 *	__sk_run_filter - run a filter on a given context

 *	@ctx: buffer to run the filter on
@@ -142,17 +156,6 @@ unsigned int __sk_run_filter(void *ctx, const struct sock_filter_int *insn) 
{

	u64 stack[MAX_BPF_STACK / sizeof(u64)];

	u64 regs[MAX_BPF_REG], tmp;

	void *ptr;

	int off;



#define K  insn->imm

#define A  regs[insn->a_reg]

#define X  regs[insn->x_reg]

#define R0 regs[0]



#define CONT	 ({insn++; goto select_insn; })

#define CONT_JMP ({insn++; goto select_insn; })



	static const void *jumptable[256] = {

		[0 ... 255] = &&default_label,

		/* Now overwrite non-defaults ... */
@@ -246,11 +249,18 @@ unsigned int __sk_run_filter(void *ctx, const struct sock_filter_int *insn) 
		DL(LD, IND, B),

#undef DL

	};

	void *ptr;

	int off;



	regs[FP_REG]  = (u64) (unsigned long) &stack[ARRAY_SIZE(stack)];

	regs[ARG1_REG] = (u64) (unsigned long) ctx;

	regs[A_REG] = 0;

	regs[X_REG] = 0;

#define CONT	 ({ insn++; goto select_insn; })

#define CONT_JMP ({ insn++; goto select_insn; })



	FP = (u64) (unsigned long) &stack[ARRAY_SIZE(stack)];

	ARG1 = (u64) (unsigned long) ctx;



	/* Register for user BPF programs need to be reset first. */

	regs[BPF_REG_A] = 0;

	regs[BPF_REG_X] = 0;



select_insn:

	goto *jumptable[insn->code];
@@ -375,8 +385,7 @@ select_insn: 
		/* Function call scratches R1-R5 registers, preserves R6-R9,

		 * and stores return value into R0.

		 */

		R0 = (__bpf_call_base + insn->imm)(regs[1], regs[2], regs[3],

						   regs[4], regs[5]);

		R0 = (__bpf_call_base + insn->imm)(R1, R2, R3, R4, R5);

		CONT;



	/* JMP */
@@ -500,7 +509,7 @@ select_insn: 
load_word:

		/* BPF_LD + BPD_ABS and BPF_LD + BPF_IND insns are only

		 * appearing in the programs where ctx == skb. All programs

		 * keep 'ctx' in regs[CTX_REG] == R6, sk_convert_filter()

		 * keep 'ctx' in regs[BPF_REG_CTX] == R6, sk_convert_filter()

		 * saves it in R6, internal BPF verifier will check that

		 * R6 == ctx.

		 *
@@ -556,13 +565,6 @@ load_byte: 
		/* If we ever reach this, we have a bug somewhere. */

		WARN_RATELIMIT(1, "unknown opcode %02x\n", insn->code);

		return 0;

#undef CONT_JMP

#undef CONT



#undef R0

#undef X

#undef A

#undef K

}



u32 sk_run_filter_int_seccomp(const struct seccomp_data *ctx,
@@ -594,14 +596,14 @@ static unsigned int pkt_type_offset(void) 
	return -1;

}



static u64 __skb_get_pay_offset(u64 ctx, u64 A, u64 X, u64 r4, u64 r5)

static u64 __skb_get_pay_offset(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)

{

	struct sk_buff *skb = (struct sk_buff *)(long) ctx;



	return __skb_get_poff(skb);

}



static u64 __skb_get_nlattr(u64 ctx, u64 A, u64 X, u64 r4, u64 r5)

static u64 __skb_get_nlattr(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)

{

	struct sk_buff *skb = (struct sk_buff *)(long) ctx;

	struct nlattr *nla;
@@ -612,17 +614,17 @@ static u64 __skb_get_nlattr(u64 ctx, u64 A, u64 X, u64 r4, u64 r5) 
	if (skb->len < sizeof(struct nlattr))

		return 0;



	if (A > skb->len - sizeof(struct nlattr))

	if (a > skb->len - sizeof(struct nlattr))

		return 0;



	nla = nla_find((struct nlattr *) &skb->data[A], skb->len - A, X);

	nla = nla_find((struct nlattr *) &skb->data[a], skb->len - a, x);

	if (nla)

		return (void *) nla - (void *) skb->data;



	return 0;

}



static u64 __skb_get_nlattr_nest(u64 ctx, u64 A, u64 X, u64 r4, u64 r5)

static u64 __skb_get_nlattr_nest(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)

{

	struct sk_buff *skb = (struct sk_buff *)(long) ctx;

	struct nlattr *nla;
@@ -633,27 +635,27 @@ static u64 __skb_get_nlattr_nest(u64 ctx, u64 A, u64 X, u64 r4, u64 r5) 
	if (skb->len < sizeof(struct nlattr))

		return 0;



	if (A > skb->len - sizeof(struct nlattr))

	if (a > skb->len - sizeof(struct nlattr))

		return 0;



	nla = (struct nlattr *) &skb->data[A];

	if (nla->nla_len > skb->len - A)

	nla = (struct nlattr *) &skb->data[a];

	if (nla->nla_len > skb->len - a)

		return 0;



	nla = nla_find_nested(nla, X);

	nla = nla_find_nested(nla, x);

	if (nla)

		return (void *) nla - (void *) skb->data;



	return 0;

}



static u64 __get_raw_cpu_id(u64 ctx, u64 A, u64 X, u64 r4, u64 r5)

static u64 __get_raw_cpu_id(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)

{

	return raw_smp_processor_id();

}



/* note that this only generates 32-bit random numbers */

static u64 __get_random_u32(u64 ctx, u64 A, u64 X, u64 r4, u64 r5)

static u64 __get_random_u32(u64 ctx, u64 a, u64 x, u64 r4, u64 r5)

{

	return (u64)prandom_u32();

}
@@ -668,28 +670,28 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);



		insn->code = BPF_LDX | BPF_MEM | BPF_H;

		insn->a_reg = A_REG;

		insn->x_reg = CTX_REG;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, protocol);

		insn++;



		/* A = ntohs(A) [emitting a nop or swap16] */

		insn->code = BPF_ALU | BPF_END | BPF_FROM_BE;

		insn->a_reg = A_REG;

		insn->a_reg = BPF_REG_A;

		insn->imm = 16;

		break;



	case SKF_AD_OFF + SKF_AD_PKTTYPE:

		insn->code = BPF_LDX | BPF_MEM | BPF_B;

		insn->a_reg = A_REG;

		insn->x_reg = CTX_REG;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = pkt_type_offset();

		if (insn->off < 0)

			return false;

		insn++;



		insn->code = BPF_ALU | BPF_AND | BPF_K;

		insn->a_reg = A_REG;

		insn->a_reg = BPF_REG_A;

		insn->imm = PKT_TYPE_MAX;

		break;
@@ -699,13 +701,13 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
			insn->code = BPF_LDX | BPF_MEM | BPF_DW;

		else

			insn->code = BPF_LDX | BPF_MEM | BPF_W;

		insn->a_reg = TMP_REG;

		insn->x_reg = CTX_REG;

		insn->a_reg = BPF_REG_TMP;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, dev);

		insn++;



		insn->code = BPF_JMP | BPF_JNE | BPF_K;

		insn->a_reg = TMP_REG;

		insn->a_reg = BPF_REG_TMP;

		insn->imm = 0;

		insn->off = 1;

		insn++;
@@ -716,8 +718,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
		BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, ifindex) != 4);

		BUILD_BUG_ON(FIELD_SIZEOF(struct net_device, type) != 2);



		insn->a_reg = A_REG;

		insn->x_reg = TMP_REG;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_TMP;



		if (fp->k == SKF_AD_OFF + SKF_AD_IFINDEX) {

			insn->code = BPF_LDX | BPF_MEM | BPF_W;
@@ -732,8 +734,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);



		insn->code = BPF_LDX | BPF_MEM | BPF_W;

		insn->a_reg = A_REG;

		insn->x_reg = CTX_REG;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, mark);

		break;
@@ -741,8 +743,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);



		insn->code = BPF_LDX | BPF_MEM | BPF_W;

		insn->a_reg = A_REG;

		insn->x_reg = CTX_REG;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, hash);

		break;
@@ -750,8 +752,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, queue_mapping) != 2);



		insn->code = BPF_LDX | BPF_MEM | BPF_H;

		insn->a_reg = A_REG;

		insn->x_reg = CTX_REG;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, queue_mapping);

		break;
@@ -760,8 +762,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);



		insn->code = BPF_LDX | BPF_MEM | BPF_H;

		insn->a_reg = A_REG;

		insn->x_reg = CTX_REG;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_CTX;

		insn->off = offsetof(struct sk_buff, vlan_tci);

		insn++;
@@ -769,16 +771,16 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 


		if (fp->k == SKF_AD_OFF + SKF_AD_VLAN_TAG) {

			insn->code = BPF_ALU | BPF_AND | BPF_K;

			insn->a_reg = A_REG;

			insn->a_reg = BPF_REG_A;

			insn->imm = ~VLAN_TAG_PRESENT;

		} else {

			insn->code = BPF_ALU | BPF_RSH | BPF_K;

			insn->a_reg = A_REG;

			insn->a_reg = BPF_REG_A;

			insn->imm = 12;

			insn++;



			insn->code = BPF_ALU | BPF_AND | BPF_K;

			insn->a_reg = A_REG;

			insn->a_reg = BPF_REG_A;

			insn->imm = 1;

		}

		break;
@@ -790,20 +792,20 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
	case SKF_AD_OFF + SKF_AD_RANDOM:

		/* arg1 = ctx */

		insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

		insn->a_reg = ARG1_REG;

		insn->x_reg = CTX_REG;

		insn->a_reg = BPF_REG_ARG1;

		insn->x_reg = BPF_REG_CTX;

		insn++;



		/* arg2 = A */

		insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

		insn->a_reg = ARG2_REG;

		insn->x_reg = A_REG;

		insn->a_reg = BPF_REG_ARG2;

		insn->x_reg = BPF_REG_A;

		insn++;



		/* arg3 = X */

		insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

		insn->a_reg = ARG3_REG;

		insn->x_reg = X_REG;

		insn->a_reg = BPF_REG_ARG3;

		insn->x_reg = BPF_REG_X;

		insn++;



		/* Emit call(ctx, arg2=A, arg3=X) */
@@ -829,8 +831,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 


	case SKF_AD_OFF + SKF_AD_ALU_XOR_X:

		insn->code = BPF_ALU | BPF_XOR | BPF_X;

		insn->a_reg = A_REG;

		insn->x_reg = X_REG;

		insn->a_reg = BPF_REG_A;

		insn->x_reg = BPF_REG_X;

		break;



	default:
@@ -880,7 +882,7 @@ int sk_convert_filter(struct sock_filter *prog, int len, 
	u8 bpf_src;



	BUILD_BUG_ON(BPF_MEMWORDS * sizeof(u32) > MAX_BPF_STACK);

	BUILD_BUG_ON(FP_REG + 1 != MAX_BPF_REG);

	BUILD_BUG_ON(BPF_REG_FP + 1 != MAX_BPF_REG);



	if (len <= 0 || len >= BPF_MAXINSNS)

		return -EINVAL;
@@ -897,8 +899,8 @@ do_pass: 


	if (new_insn) {

		new_insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

		new_insn->a_reg = CTX_REG;

		new_insn->x_reg = ARG1_REG;

		new_insn->a_reg = BPF_REG_CTX;

		new_insn->x_reg = BPF_REG_ARG1;

	}

	new_insn++;
@@ -948,8 +950,8 @@ do_pass: 
				break;



			insn->code = fp->code;

			insn->a_reg = A_REG;

			insn->x_reg = X_REG;

			insn->a_reg = BPF_REG_A;

			insn->x_reg = BPF_REG_X;

			insn->imm = fp->k;

			break;
@@ -983,16 +985,16 @@ do_pass: 
				 * in compare insn.

				 */

				insn->code = BPF_ALU | BPF_MOV | BPF_K;

				insn->a_reg = TMP_REG;

				insn->a_reg = BPF_REG_TMP;

				insn->imm = fp->k;

				insn++;



				insn->a_reg = A_REG;

				insn->x_reg = TMP_REG;

				insn->a_reg = BPF_REG_A;

				insn->x_reg = BPF_REG_TMP;

				bpf_src = BPF_X;

			} else {

				insn->a_reg = A_REG;

				insn->x_reg = X_REG;

				insn->a_reg = BPF_REG_A;

				insn->x_reg = BPF_REG_X;

				insn->imm = fp->k;

				bpf_src = BPF_SRC(fp->code);

			}
@@ -1027,33 +1029,33 @@ do_pass: 
		/* ldxb 4 * ([14] & 0xf) is remaped into 6 insns. */

		case BPF_LDX | BPF_MSH | BPF_B:

			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = TMP_REG;

			insn->x_reg = A_REG;

			insn->a_reg = BPF_REG_TMP;

			insn->x_reg = BPF_REG_A;

			insn++;



			insn->code = BPF_LD | BPF_ABS | BPF_B;

			insn->a_reg = A_REG;

			insn->a_reg = BPF_REG_A;

			insn->imm = fp->k;

			insn++;



			insn->code = BPF_ALU | BPF_AND | BPF_K;

			insn->a_reg = A_REG;

			insn->a_reg = BPF_REG_A;

			insn->imm = 0xf;

			insn++;



			insn->code = BPF_ALU | BPF_LSH | BPF_K;

			insn->a_reg = A_REG;

			insn->a_reg = BPF_REG_A;

			insn->imm = 2;

			insn++;



			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = X_REG;

			insn->x_reg = A_REG;

			insn->a_reg = BPF_REG_X;

			insn->x_reg = BPF_REG_A;

			insn++;



			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = A_REG;

			insn->x_reg = TMP_REG;

			insn->a_reg = BPF_REG_A;

			insn->x_reg = BPF_REG_TMP;

			break;



		/* RET_K, RET_A are remaped into 2 insns. */
@@ -1063,7 +1065,7 @@ do_pass: 
				     (BPF_RVAL(fp->code) == BPF_K ?

				      BPF_K : BPF_X);

			insn->a_reg = 0;

			insn->x_reg = A_REG;

			insn->x_reg = BPF_REG_A;

			insn->imm = fp->k;

			insn++;
@@ -1074,8 +1076,9 @@ do_pass: 
		case BPF_ST:

		case BPF_STX:

			insn->code = BPF_STX | BPF_MEM | BPF_W;

			insn->a_reg = FP_REG;

			insn->x_reg = fp->code == BPF_ST ? A_REG : X_REG;

			insn->a_reg = BPF_REG_FP;

			insn->x_reg = fp->code == BPF_ST ?

				      BPF_REG_A : BPF_REG_X;

			insn->off = -(BPF_MEMWORDS - fp->k) * 4;

			break;
@@ -1084,8 +1087,8 @@ do_pass: 
		case BPF_LDX | BPF_MEM:

			insn->code = BPF_LDX | BPF_MEM | BPF_W;

			insn->a_reg = BPF_CLASS(fp->code) == BPF_LD ?

				      A_REG : X_REG;

			insn->x_reg = FP_REG;

				      BPF_REG_A : BPF_REG_X;

			insn->x_reg = BPF_REG_FP;

			insn->off = -(BPF_MEMWORDS - fp->k) * 4;

			break;
@@ -1094,22 +1097,22 @@ do_pass: 
		case BPF_LDX | BPF_IMM:

			insn->code = BPF_ALU | BPF_MOV | BPF_K;

			insn->a_reg = BPF_CLASS(fp->code) == BPF_LD ?

				      A_REG : X_REG;

				      BPF_REG_A : BPF_REG_X;

			insn->imm = fp->k;

			break;



		/* X = A */

		case BPF_MISC | BPF_TAX:

			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = X_REG;

			insn->x_reg = A_REG;

			insn->a_reg = BPF_REG_X;

			insn->x_reg = BPF_REG_A;

			break;



		/* A = X */

		case BPF_MISC | BPF_TXA:

			insn->code = BPF_ALU64 | BPF_MOV | BPF_X;

			insn->a_reg = A_REG;

			insn->x_reg = X_REG;

			insn->a_reg = BPF_REG_A;

			insn->x_reg = BPF_REG_X;

			break;



		/* A = skb->len or X = skb->len */
@@ -1117,16 +1120,16 @@ do_pass: 
		case BPF_LDX | BPF_W | BPF_LEN:

			insn->code = BPF_LDX | BPF_MEM | BPF_W;

			insn->a_reg = BPF_CLASS(fp->code) == BPF_LD ?

				      A_REG : X_REG;

			insn->x_reg = CTX_REG;

				      BPF_REG_A : BPF_REG_X;

			insn->x_reg = BPF_REG_CTX;

			insn->off = offsetof(struct sk_buff, len);

			break;



		/* access seccomp_data fields */

		case BPF_LDX | BPF_ABS | BPF_W:

			insn->code = BPF_LDX | BPF_MEM | BPF_W;

			insn->a_reg = A_REG;

			insn->x_reg = CTX_REG;

			insn->a_reg = BPF_REG_A;

			insn->x_reg = BPF_REG_CTX;

			insn->off = fp->k;

			break;

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