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net: filter: x86: split bpf_jit_compile()
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Split bpf_jit_compile() into two functions to improve readability
of for(pass++) loop. The change follows similar style of JIT compilers
for arm, powerpc, s390

The body of new do_jit() was not reformatted to reduce noise
in this patch, since the following patch replaces most of it.

Tested with BPF testsuite.

Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Alexei Starovoitov authored and David S. Miller committed May 15, 2014
1 parent 9509b1c commit f3c2af7
Showing 1 changed file with 92 additions and 65 deletions.
157 changes: 92 additions & 65 deletions arch/x86/net/bpf_jit_comp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -178,41 +178,26 @@ static struct bpf_binary_header *bpf_alloc_binary(unsigned int proglen,
return header;
}

void bpf_jit_compile(struct sk_filter *fp)
struct jit_context {
unsigned int cleanup_addr; /* epilogue code offset */
int pc_ret0; /* bpf index of first RET #0 instruction (if any) */
u8 seen;
};

static int do_jit(struct sk_filter *bpf_prog, int *addrs, u8 *image,
int oldproglen, struct jit_context *ctx)
{
const struct sock_filter *filter = bpf_prog->insns;
int flen = bpf_prog->len;
u8 temp[64];
u8 *prog;
unsigned int proglen, oldproglen = 0;
int ilen, i;
int ilen, i, proglen;
int t_offset, f_offset;
u8 t_op, f_op, seen = 0, pass;
u8 *image = NULL;
struct bpf_binary_header *header = NULL;
u8 t_op, f_op, seen = 0;
u8 *func;
int pc_ret0 = -1; /* bpf index of first RET #0 instruction (if any) */
unsigned int cleanup_addr; /* epilogue code offset */
unsigned int *addrs;
const struct sock_filter *filter = fp->insns;
int flen = fp->len;

if (!bpf_jit_enable)
return;

addrs = kmalloc(flen * sizeof(*addrs), GFP_KERNEL);
if (addrs == NULL)
return;

/* Before first pass, make a rough estimation of addrs[]
* each bpf instruction is translated to less than 64 bytes
*/
for (proglen = 0, i = 0; i < flen; i++) {
proglen += 64;
addrs[i] = proglen;
}
cleanup_addr = proglen; /* epilogue address */
unsigned int cleanup_addr = ctx->cleanup_addr;
u8 seen_or_pass0 = ctx->seen;

for (pass = 0; pass < 10; pass++) {
u8 seen_or_pass0 = (pass == 0) ? (SEEN_XREG | SEEN_DATAREF | SEEN_MEM) : seen;
/* no prologue/epilogue for trivial filters (RET something) */
proglen = 0;
prog = temp;
Expand Down Expand Up @@ -325,12 +310,12 @@ void bpf_jit_compile(struct sk_filter *fp)
case BPF_S_ALU_DIV_X: /* A /= X; */
seen |= SEEN_XREG;
EMIT2(0x85, 0xdb); /* test %ebx,%ebx */
if (pc_ret0 > 0) {
if (ctx->pc_ret0 > 0) {
/* addrs[pc_ret0 - 1] is start address of target
* (addrs[i] - 4) is the address following this jmp
* ("xor %edx,%edx; div %ebx" being 4 bytes long)
*/
EMIT_COND_JMP(X86_JE, addrs[pc_ret0 - 1] -
EMIT_COND_JMP(X86_JE, addrs[ctx->pc_ret0 - 1] -
(addrs[i] - 4));
} else {
EMIT_COND_JMP(X86_JNE, 2 + 5);
Expand All @@ -342,12 +327,12 @@ void bpf_jit_compile(struct sk_filter *fp)
case BPF_S_ALU_MOD_X: /* A %= X; */
seen |= SEEN_XREG;
EMIT2(0x85, 0xdb); /* test %ebx,%ebx */
if (pc_ret0 > 0) {
if (ctx->pc_ret0 > 0) {
/* addrs[pc_ret0 - 1] is start address of target
* (addrs[i] - 6) is the address following this jmp
* ("xor %edx,%edx; div %ebx;mov %edx,%eax" being 6 bytes long)
*/
EMIT_COND_JMP(X86_JE, addrs[pc_ret0 - 1] -
EMIT_COND_JMP(X86_JE, addrs[ctx->pc_ret0 - 1] -
(addrs[i] - 6));
} else {
EMIT_COND_JMP(X86_JNE, 2 + 5);
Expand Down Expand Up @@ -441,8 +426,8 @@ void bpf_jit_compile(struct sk_filter *fp)
break;
case BPF_S_RET_K:
if (!K) {
if (pc_ret0 == -1)
pc_ret0 = i;
if (ctx->pc_ret0 == -1)
ctx->pc_ret0 = i;
CLEAR_A();
} else {
EMIT1_off32(0xb8, K); /* mov $imm32,%eax */
Expand Down Expand Up @@ -603,7 +588,7 @@ void bpf_jit_compile(struct sk_filter *fp)
int off = pkt_type_offset();

if (off < 0)
goto out;
return -EINVAL;
if (is_imm8(off)) {
/* movzbl off8(%rdi),%eax */
EMIT4(0x0f, 0xb6, 0x47, off);
Expand Down Expand Up @@ -725,36 +710,79 @@ cond_branch: f_offset = addrs[i + filter[i].jf] - addrs[i];
}
EMIT_COND_JMP(f_op, f_offset);
break;
default:
/* hmm, too complex filter, give up with jit compiler */
goto out;
}
ilen = prog - temp;
if (image) {
if (unlikely(proglen + ilen > oldproglen)) {
pr_err("bpb_jit_compile fatal error\n");
kfree(addrs);
module_free(NULL, header);
return;
}
memcpy(image + proglen, temp, ilen);
default:
/* hmm, too complex filter, give up with jit compiler */
return -EINVAL;
}
ilen = prog - temp;
if (image) {
if (unlikely(proglen + ilen > oldproglen)) {
pr_err("bpb_jit_compile fatal error\n");
return -EFAULT;
}
proglen += ilen;
addrs[i] = proglen;
prog = temp;
memcpy(image + proglen, temp, ilen);
}
/* last bpf instruction is always a RET :
* use it to give the cleanup instruction(s) addr
*/
cleanup_addr = proglen - 1; /* ret */
if (seen_or_pass0)
cleanup_addr -= 1; /* leaveq */
if (seen_or_pass0 & SEEN_XREG)
cleanup_addr -= 4; /* mov -8(%rbp),%rbx */
proglen += ilen;
addrs[i] = proglen;
prog = temp;
}
/* last bpf instruction is always a RET :
* use it to give the cleanup instruction(s) addr
*/
ctx->cleanup_addr = proglen - 1; /* ret */
if (seen_or_pass0)
ctx->cleanup_addr -= 1; /* leaveq */
if (seen_or_pass0 & SEEN_XREG)
ctx->cleanup_addr -= 4; /* mov -8(%rbp),%rbx */

ctx->seen = seen;

return proglen;
}

void bpf_jit_compile(struct sk_filter *prog)
{
struct bpf_binary_header *header = NULL;
int proglen, oldproglen = 0;
struct jit_context ctx = {};
u8 *image = NULL;
int *addrs;
int pass;
int i;

if (!bpf_jit_enable)
return;

if (!prog || !prog->len)
return;

addrs = kmalloc(prog->len * sizeof(*addrs), GFP_KERNEL);
if (!addrs)
return;

/* Before first pass, make a rough estimation of addrs[]
* each bpf instruction is translated to less than 64 bytes
*/
for (proglen = 0, i = 0; i < prog->len; i++) {
proglen += 64;
addrs[i] = proglen;
}
ctx.cleanup_addr = proglen;
ctx.seen = SEEN_XREG | SEEN_DATAREF | SEEN_MEM;
ctx.pc_ret0 = -1;

for (pass = 0; pass < 10; pass++) {
proglen = do_jit(prog, addrs, image, oldproglen, &ctx);
if (proglen <= 0) {
image = NULL;
if (header)
module_free(NULL, header);
goto out;
}
if (image) {
if (proglen != oldproglen)
pr_err("bpb_jit_compile proglen=%u != oldproglen=%u\n", proglen, oldproglen);
pr_err("bpf_jit: proglen=%d != oldproglen=%d\n",
proglen, oldproglen);
break;
}
if (proglen == oldproglen) {
Expand All @@ -766,17 +794,16 @@ cond_branch: f_offset = addrs[i + filter[i].jf] - addrs[i];
}

if (bpf_jit_enable > 1)
bpf_jit_dump(flen, proglen, pass, image);
bpf_jit_dump(prog->len, proglen, 0, image);

if (image) {
bpf_flush_icache(header, image + proglen);
set_memory_ro((unsigned long)header, header->pages);
fp->bpf_func = (void *)image;
fp->jited = 1;
prog->bpf_func = (void *)image;
prog->jited = 1;
}
out:
kfree(addrs);
return;
}

static void bpf_jit_free_deferred(struct work_struct *work)
Expand Down

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