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net: filter: make register naming more comprehensible

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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: Daniel Borkmann <dborkman@redhat.com>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2014-05-01 18:34:19 +02:00 committed by David S. Miller
parent 5bcfedf06f
commit 30743837dd
2 changed files with 145 additions and 114 deletions
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44
include/linux/filter.h
View File

@ -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,

215
net/core/filter.c
View File

@ -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 @@ unsigned int __sk_run_filter(void *ctx, const struct sock_filter_int *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 @@ unsigned int __sk_run_filter(void *ctx, const struct sock_filter_int *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 @@ unsigned int __sk_run_filter(void *ctx, const struct sock_filter_int *insn)
/* 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 @@ int sk_convert_filter(struct sock_filter *prog, int len,
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 @@ int sk_convert_filter(struct sock_filter *prog, int len,
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 @@ int sk_convert_filter(struct sock_filter *prog, int len,
* 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 @@ int sk_convert_filter(struct sock_filter *prog, int len,
/* 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 @@ int sk_convert_filter(struct sock_filter *prog, int len,
(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 @@ int sk_convert_filter(struct sock_filter *prog, int len,
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 @@ int sk_convert_filter(struct sock_filter *prog, int len,
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 @@ int sk_convert_filter(struct sock_filter *prog, int len,
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 @@ int sk_convert_filter(struct sock_filter *prog, int len,
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;