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nfp: bpf: allow stack accesses via modified stack registers

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As long as the verifier tells us the stack offset exactly we
can render the LMEM reads quite easily.  Simply make sure that
the offset is constant for a given instruction and add it to
the instruction's offset.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Kicinski 2017-10-23 11:58:11 -07:00 committed by David S. Miller
parent 9a90c83c09
commit d348848063
3 changed files with 33 additions and 17 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
drivers/net/ethernet/netronome/nfp/bpf/jit.c
View File

@ -771,9 +771,10 @@ wrp_lmem_store(struct nfp_prog *nfp_prog, u8 src, u8 src_byte, s32 off,
static int
mem_op_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
unsigned int size, u8 gpr, bool clr_gpr, lmem_step step)
unsigned int size, unsigned int ptr_off, u8 gpr, bool clr_gpr,
lmem_step step)
{
s32 off = nfp_prog->stack_depth + meta->insn.off;
s32 off = nfp_prog->stack_depth + meta->insn.off + ptr_off;
bool first = true, last;
u8 prev_gpr = 255;
u32 gpr_byte = 0;
@ -1311,10 +1312,10 @@ static int data_ind_ld4(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
static int
mem_ldx_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
unsigned int size)
unsigned int size, unsigned int ptr_off)
{
return mem_op_stack(nfp_prog, meta, size, meta->insn.dst_reg * 2, true,
wrp_lmem_load);
return mem_op_stack(nfp_prog, meta, size, ptr_off,
meta->insn.dst_reg * 2, true, wrp_lmem_load);
}
static int mem_ldx_skb(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
@ -1401,7 +1402,8 @@ mem_ldx(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
return mem_ldx_data(nfp_prog, meta, size);
if (meta->ptr.type == PTR_TO_STACK)
return mem_ldx_stack(nfp_prog, meta, size);
return mem_ldx_stack(nfp_prog, meta, size,
meta->ptr.off + meta->ptr.var_off.value);
return -EOPNOTSUPP;
}
@ -1482,10 +1484,10 @@ mem_stx_data(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
static int
mem_stx_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
unsigned int size)
unsigned int size, unsigned int ptr_off)
{
return mem_op_stack(nfp_prog, meta, size, meta->insn.src_reg * 2, false,
wrp_lmem_store);
return mem_op_stack(nfp_prog, meta, size, ptr_off,
meta->insn.src_reg * 2, false, wrp_lmem_store);
}
static int
@ -1496,7 +1498,8 @@ mem_stx(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
return mem_stx_data(nfp_prog, meta, size);
if (meta->ptr.type == PTR_TO_STACK)
return mem_stx_stack(nfp_prog, meta, size);
return mem_stx_stack(nfp_prog, meta, size,
meta->ptr.off + meta->ptr.var_off.value);
return -EOPNOTSUPP;
}

3
drivers/net/ethernet/netronome/nfp/bpf/main.h
View File

@ -56,6 +56,7 @@ enum br_special {
enum static_regs {
STATIC_REG_IMM = 21, /* Bank AB */
STATIC_REG_STACK = 22, /* Bank A */
STATIC_REG_PKT_LEN = 22, /* Bank B */
};
@ -74,6 +75,8 @@ enum nfp_bpf_action_type {
#define pv_len(np) reg_lm(1, PKT_VEC_PKT_LEN)
#define pv_ctm_ptr(np) reg_lm(1, PKT_VEC_PKT_PTR)
#define stack_reg(np) reg_a(STATIC_REG_STACK)
#define stack_imm(np) imm_b(np)
#define plen_reg(np) reg_b(STATIC_REG_PKT_LEN)
#define pptr_reg(np) pv_ctm_ptr(np)
#define imm_a(np) reg_a(STATIC_REG_IMM)

24
drivers/net/ethernet/netronome/nfp/bpf/verifier.c
View File

@ -111,19 +111,29 @@ nfp_bpf_check_exit(struct nfp_prog *nfp_prog,
return 0;
}
static int nfp_bpf_check_stack_access(const struct bpf_reg_state *reg)
static int
nfp_bpf_check_stack_access(struct nfp_insn_meta *meta,
const struct bpf_reg_state *reg)
{
s32 old_off, new_off;
if (!tnum_is_const(reg->var_off)) {
pr_info("variable ptr stack access\n");
return -EINVAL;
}
if (reg->var_off.value || reg->off) {
pr_info("stack access via modified register\n");
return -EINVAL;
}
if (meta->ptr.type == NOT_INIT)
return 0;
return 0;
old_off = meta->ptr.off + meta->ptr.var_off.value;
new_off = reg->off + reg->var_off.value;
if (old_off == new_off)
return 0;
pr_info("stack access changed location was:%d is:%d\n",
old_off, new_off);
return -EINVAL;
}
static int
@ -141,7 +151,7 @@ nfp_bpf_check_ptr(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
}
if (reg->type == PTR_TO_STACK) {
err = nfp_bpf_check_stack_access(reg);
err = nfp_bpf_check_stack_access(meta, reg);
if (err)
return err;
}