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Message-Id: <3dd23ead374c4f5ca5cfa6dfd6902538144b8df9.1463158442.git.daniel@iogearbox.net>
Date: Fri, 13 May 2016 19:08:33 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: davem@...emloft.net
Cc: alexei.starovoitov@...il.com, elena.reshetova@...el.com,
zlim.lnx@...il.com, yang.shi@...aro.org,
holzheu@...ux.vnet.ibm.com, tgraf@...g.ch, netdev@...r.kernel.org,
Daniel Borkmann <daniel@...earbox.net>
Subject: [PATCH net-next 08/10] bpf, x86: add support for constant blinding
This patch adds recently added constant blinding helpers into the
x86 eBPF JIT. In the bpf_int_jit_compile() path, requirements are
to utilize bpf_jit_blind_constants()/bpf_jit_prog_release_other()
pair for rewriting the program into a blinded one, and to map the
BPF_REG_AX register to a CPU register. The mapping of BPF_REG_AX
is at non-callee saved register r10, and thus shared with cached
skb->data used for ld_abs/ind and not in every program type needed.
When blinding is not used, there's zero additional overhead in the
generated image.
Signed-off-by: Daniel Borkmann <daniel@...earbox.net>
Acked-by: Alexei Starovoitov <ast@...nel.org>
---
arch/x86/net/bpf_jit_comp.c | 66 ++++++++++++++++++++++++++++++++++++---------
1 file changed, 53 insertions(+), 13 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 6b2d23e..fe04a04 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -110,11 +110,16 @@ static void bpf_flush_icache(void *start, void *end)
((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative_offset : func) : func##_positive_offset)
/* pick a register outside of BPF range for JIT internal work */
-#define AUX_REG (MAX_BPF_REG + 1)
+#define AUX_REG (MAX_BPF_JIT_REG + 1)
-/* the following table maps BPF registers to x64 registers.
- * x64 register r12 is unused, since if used as base address register
- * in load/store instructions, it always needs an extra byte of encoding
+/* The following table maps BPF registers to x64 registers.
+ *
+ * x64 register r12 is unused, since if used as base address
+ * register in load/store instructions, it always needs an
+ * extra byte of encoding and is callee saved.
+ *
+ * r9 caches skb->len - skb->data_len
+ * r10 caches skb->data, and used for blinding (if enabled)
*/
static const int reg2hex[] = {
[BPF_REG_0] = 0, /* rax */
@@ -128,6 +133,7 @@ static const int reg2hex[] = {
[BPF_REG_8] = 6, /* r14 callee saved */
[BPF_REG_9] = 7, /* r15 callee saved */
[BPF_REG_FP] = 5, /* rbp readonly */
+ [BPF_REG_AX] = 2, /* r10 temp register */
[AUX_REG] = 3, /* r11 temp register */
};
@@ -141,7 +147,8 @@ static bool is_ereg(u32 reg)
BIT(AUX_REG) |
BIT(BPF_REG_7) |
BIT(BPF_REG_8) |
- BIT(BPF_REG_9));
+ BIT(BPF_REG_9) |
+ BIT(BPF_REG_AX));
}
/* add modifiers if 'reg' maps to x64 registers r8..r15 */
@@ -182,6 +189,7 @@ static void jit_fill_hole(void *area, unsigned int size)
struct jit_context {
int cleanup_addr; /* epilogue code offset */
bool seen_ld_abs;
+ bool seen_ax_reg;
};
/* maximum number of bytes emitted while JITing one eBPF insn */
@@ -345,6 +353,7 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
struct bpf_insn *insn = bpf_prog->insnsi;
int insn_cnt = bpf_prog->len;
bool seen_ld_abs = ctx->seen_ld_abs | (oldproglen == 0);
+ bool seen_ax_reg = ctx->seen_ax_reg | (oldproglen == 0);
bool seen_exit = false;
u8 temp[BPF_MAX_INSN_SIZE + BPF_INSN_SAFETY];
int i, cnt = 0;
@@ -367,6 +376,9 @@ static int do_jit(struct bpf_prog *bpf_prog, int *addrs, u8 *image,
int ilen;
u8 *func;
+ if (dst_reg == BPF_REG_AX || src_reg == BPF_REG_AX)
+ ctx->seen_ax_reg = seen_ax_reg = true;
+
switch (insn->code) {
/* ALU */
case BPF_ALU | BPF_ADD | BPF_X:
@@ -1002,6 +1014,10 @@ common_load:
* sk_load_* helpers also use %r10 and %r9d.
* See bpf_jit.S
*/
+ if (seen_ax_reg)
+ /* r10 = skb->data, mov %r10, off32(%rbx) */
+ EMIT3_off32(0x4c, 0x8b, 0x93,
+ offsetof(struct sk_buff, data));
EMIT1_off32(0xE8, jmp_offset); /* call */
break;
@@ -1076,19 +1092,34 @@ void bpf_jit_compile(struct bpf_prog *prog)
struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
{
struct bpf_binary_header *header = NULL;
+ struct bpf_prog *tmp, *orig_prog = prog;
int proglen, oldproglen = 0;
struct jit_context ctx = {};
+ bool tmp_blinded = false;
u8 *image = NULL;
int *addrs;
int pass;
int i;
if (!bpf_jit_enable)
- return prog;
+ return orig_prog;
+
+ tmp = bpf_jit_blind_constants(prog);
+ /* If blinding was requested and we failed during blinding,
+ * we must fall back to the interpreter.
+ */
+ if (IS_ERR(tmp))
+ return orig_prog;
+ if (tmp != prog) {
+ tmp_blinded = true;
+ prog = tmp;
+ }
addrs = kmalloc(prog->len * sizeof(*addrs), GFP_KERNEL);
- if (!addrs)
- return prog;
+ if (!addrs) {
+ prog = orig_prog;
+ goto out;
+ }
/* Before first pass, make a rough estimation of addrs[]
* each bpf instruction is translated to less than 64 bytes
@@ -1110,21 +1141,25 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
image = NULL;
if (header)
bpf_jit_binary_free(header);
- goto out;
+ prog = orig_prog;
+ goto out_addrs;
}
if (image) {
if (proglen != oldproglen) {
pr_err("bpf_jit: proglen=%d != oldproglen=%d\n",
proglen, oldproglen);
- goto out;
+ prog = orig_prog;
+ goto out_addrs;
}
break;
}
if (proglen == oldproglen) {
header = bpf_jit_binary_alloc(proglen, &image,
1, jit_fill_hole);
- if (!header)
- goto out;
+ if (!header) {
+ prog = orig_prog;
+ goto out_addrs;
+ }
}
oldproglen = proglen;
}
@@ -1138,8 +1173,13 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog)
prog->bpf_func = (void *)image;
prog->jited = 1;
}
-out:
+
+out_addrs:
kfree(addrs);
+out:
+ if (tmp_blinded)
+ bpf_jit_prog_release_other(prog, prog == orig_prog ?
+ tmp : orig_prog);
return prog;
}
--
1.9.3
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