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Commit b7b7013c authored by Naveen N. Rao's avatar Naveen N. Rao Committed by Michael Ellerman
Browse files

powerpc/bpf: Add support for bpf constant blinding 



In line with similar support for other architectures by Daniel Borkmann.

'MOD Default X' from test_bpf without constant blinding:
84 bytes emitted from JIT compiler (pass:3, flen:7)
d0000000058a4688 + <x>:
   0:	nop
   4:	nop
   8:	std     r27,-40(r1)
   c:	std     r28,-32(r1)
  10:	xor     r8,r8,r8
  14:	xor     r28,r28,r28
  18:	mr      r27,r3
  1c:	li      r8,66
  20:	cmpwi   r28,0
  24:	bne     0x0000000000000030
  28:	li      r8,0
  2c:	b       0x0000000000000044
  30:	divwu   r9,r8,r28
  34:	mullw   r9,r28,r9
  38:	subf    r8,r9,r8
  3c:	rotlwi  r8,r8,0
  40:	li      r8,66
  44:	ld      r27,-40(r1)
  48:	ld      r28,-32(r1)
  4c:	mr      r3,r8
  50:	blr

... and with constant blinding:
140 bytes emitted from JIT compiler (pass:3, flen:11)
d00000000bd6ab24 + <x>:
   0:	nop
   4:	nop
   8:	std     r27,-40(r1)
   c:	std     r28,-32(r1)
  10:	xor     r8,r8,r8
  14:	xor     r28,r28,r28
  18:	mr      r27,r3
  1c:	lis     r2,-22834
  20:	ori     r2,r2,36083
  24:	rotlwi  r2,r2,0
  28:	xori    r2,r2,36017
  2c:	xoris   r2,r2,42702
  30:	rotlwi  r2,r2,0
  34:	mr      r8,r2
  38:	rotlwi  r8,r8,0
  3c:	cmpwi   r28,0
  40:	bne     0x000000000000004c
  44:	li      r8,0
  48:	b       0x000000000000007c
  4c:	divwu   r9,r8,r28
  50:	mullw   r9,r28,r9
  54:	subf    r8,r9,r8
  58:	rotlwi  r8,r8,0
  5c:	lis     r2,-17137
  60:	ori     r2,r2,39065
  64:	rotlwi  r2,r2,0
  68:	xori    r2,r2,39131
  6c:	xoris   r2,r2,48399
  70:	rotlwi  r2,r2,0
  74:	mr      r8,r2
  78:	rotlwi  r8,r8,0
  7c:	ld      r27,-40(r1)
  80:	ld      r28,-32(r1)
  84:	mr      r3,r8
  88:	blr

Signed-off-by: default avatarNaveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent ce076141

arch/powerpc/net/bpf_jit64.h

+5 −4
Original line number Diff line number Diff line
@@ -39,10 +39,10 @@ 
#ifndef __ASSEMBLY__



/* BPF register usage */

#define SKB_HLEN_REG	(MAX_BPF_REG + 0)

#define SKB_DATA_REG	(MAX_BPF_REG + 1)

#define TMP_REG_1	(MAX_BPF_REG + 2)

#define TMP_REG_2	(MAX_BPF_REG + 3)

#define SKB_HLEN_REG	(MAX_BPF_JIT_REG + 0)

#define SKB_DATA_REG	(MAX_BPF_JIT_REG + 1)

#define TMP_REG_1	(MAX_BPF_JIT_REG + 2)

#define TMP_REG_2	(MAX_BPF_JIT_REG + 3)



/* BPF to ppc register mappings */

static const int b2p[] = {
@@ -62,6 +62,7 @@ static const int b2p[] = { 
	/* frame pointer aka BPF_REG_10 */

	[BPF_REG_FP] = 31,

	/* eBPF jit internal registers */

	[BPF_REG_AX] = 2,

	[SKB_HLEN_REG] = 25,

	[SKB_DATA_REG] = 26,

	[TMP_REG_1] = 9,

arch/powerpc/net/bpf_jit_comp64.c

+29 −7
Original line number Diff line number Diff line
@@ -974,21 +974,37 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) 
	int pass;

	int flen;

	struct bpf_binary_header *bpf_hdr;

	struct bpf_prog *org_fp = fp;

	struct bpf_prog *tmp_fp;

	bool bpf_blinded = false;



	if (!bpf_jit_enable)

		return fp;

		return org_fp;



	tmp_fp = bpf_jit_blind_constants(org_fp);

	if (IS_ERR(tmp_fp))

		return org_fp;



	if (tmp_fp != org_fp) {

		bpf_blinded = true;

		fp = tmp_fp;

	}



	flen = fp->len;

	addrs = kzalloc((flen+1) * sizeof(*addrs), GFP_KERNEL);

	if (addrs == NULL)

		return fp;

	if (addrs == NULL) {

		fp = org_fp;

		goto out;

	}



	memset(&cgctx, 0, sizeof(struct codegen_context));



	cgctx.idx = 0;

	cgctx.seen = 0;

	/* Scouting faux-generate pass 0 */

	if (bpf_jit_build_body(fp, 0, &cgctx, addrs))

	if (bpf_jit_build_body(fp, 0, &cgctx, addrs)) {

		/* We hit something illegal or unsupported. */

		fp = org_fp;

		goto out;

	}



	/*

	 * Pretend to build prologue, given the features we've seen.  This will
@@ -1003,8 +1019,10 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) 


	bpf_hdr = bpf_jit_binary_alloc(alloclen, &image, 4,

			bpf_jit_fill_ill_insns);

	if (!bpf_hdr)

	if (!bpf_hdr) {

		fp = org_fp;

		goto out;

	}



	code_base = (u32 *)(image + FUNCTION_DESCR_SIZE);
@@ -1041,6 +1059,10 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *fp) 


out:

	kfree(addrs);



	if (bpf_blinded)

		bpf_jit_prog_release_other(fp, fp == org_fp ? tmp_fp : org_fp);



	return fp;

}