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nfp: bpf: support stack accesses via non-constant pointers

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If stack pointer has a different value on different paths
but the alignment to words (4B) remains the same, we can
set a new LMEM access pointer to the calculated value and
access whichever word it's pointing to.

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 11:58:13 -07:00 committed by David S. Miller
parent 2df03a50f1
commit b14157eeed
3 changed files with 45 additions and 10 deletions
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41
drivers/net/ethernet/netronome/nfp/bpf/jit.c
View File

@ -832,8 +832,8 @@ 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, unsigned int ptr_off, u8 gpr, bool clr_gpr,
lmem_step step)
unsigned int size, unsigned int ptr_off, u8 gpr, u8 ptr_gpr,
bool clr_gpr, lmem_step step)
{
s32 off = nfp_prog->stack_depth + meta->insn.off + ptr_off;
bool first = true, last;
@ -844,7 +844,19 @@ mem_op_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
bool lm3 = true;
int ret;
if (off + size <= 64) {
if (meta->ptr_not_const) {
/* Use of the last encountered ptr_off is OK, they all have
* the same alignment. Depend on low bits of value being
* discarded when written to LMaddr register.
*/
stack_off_reg = ur_load_imm_any(nfp_prog, meta->insn.off,
stack_imm(nfp_prog));
emit_alu(nfp_prog, imm_b(nfp_prog),
reg_a(ptr_gpr), ALU_OP_ADD, stack_off_reg);
needs_inc = true;
} else if (off + size <= 64) {
/* We can reach bottom 64B with LMaddr0 */
lm3 = false;
} else if (round_down(off, 32) == round_down(off + size - 1, 32)) {
@ -1096,9 +1108,22 @@ static void wrp_end32(struct nfp_prog *nfp_prog, swreg reg_in, u8 gpr_out)
static int mov_reg64(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta)
{
const struct bpf_insn *insn = &meta->insn;
u8 dst = insn->dst_reg * 2;
u8 src = insn->src_reg * 2;
wrp_reg_mov(nfp_prog, insn->dst_reg * 2, insn->src_reg * 2);
wrp_reg_mov(nfp_prog, insn->dst_reg * 2 + 1, insn->src_reg * 2 + 1);
if (insn->src_reg == BPF_REG_10) {
swreg stack_depth_reg;
stack_depth_reg = ur_load_imm_any(nfp_prog,
nfp_prog->stack_depth,
stack_imm(nfp_prog));
emit_alu(nfp_prog, reg_both(dst),
stack_reg(nfp_prog), ALU_OP_ADD, stack_depth_reg);
wrp_immed(nfp_prog, reg_both(dst + 1), 0);
} else {
wrp_reg_mov(nfp_prog, dst, src);
wrp_reg_mov(nfp_prog, dst + 1, src + 1);
}
return 0;
}
@ -1413,7 +1438,8 @@ mem_ldx_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
unsigned int size, unsigned int ptr_off)
{
return mem_op_stack(nfp_prog, meta, size, ptr_off,
meta->insn.dst_reg * 2, true, wrp_lmem_load);
meta->insn.dst_reg * 2, meta->insn.src_reg * 2,
true, wrp_lmem_load);
}
static int mem_ldx_skb(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
@ -1585,7 +1611,8 @@ mem_stx_stack(struct nfp_prog *nfp_prog, struct nfp_insn_meta *meta,
unsigned int size, unsigned int ptr_off)
{
return mem_op_stack(nfp_prog, meta, size, ptr_off,
meta->insn.src_reg * 2, false, wrp_lmem_store);
meta->insn.src_reg * 2, meta->insn.dst_reg * 2,
false, wrp_lmem_store);
}
static int

2
drivers/net/ethernet/netronome/nfp/bpf/main.h
View File

@ -101,6 +101,7 @@ typedef int (*instr_cb_t)(struct nfp_prog *, struct nfp_insn_meta *);
* struct nfp_insn_meta - BPF instruction wrapper
* @insn: BPF instruction
* @ptr: pointer type for memory operations
* @ptr_not_const: pointer is not always constant
* @off: index of first generated machine instruction (in nfp_prog.prog)
* @n: eBPF instruction number
* @skip: skip this instruction (optimized out)
@ -110,6 +111,7 @@ typedef int (*instr_cb_t)(struct nfp_prog *, struct nfp_insn_meta *);
struct nfp_insn_meta {
struct bpf_insn insn;
struct bpf_reg_state ptr;
bool ptr_not_const;
unsigned int off;
unsigned short n;
bool skip;

12
drivers/net/ethernet/netronome/nfp/bpf/verifier.c
View File

@ -112,7 +112,8 @@ nfp_bpf_check_exit(struct nfp_prog *nfp_prog,
}
static int
nfp_bpf_check_stack_access(struct nfp_insn_meta *meta,
nfp_bpf_check_stack_access(struct nfp_prog *nfp_prog,
struct nfp_insn_meta *meta,
const struct bpf_reg_state *reg)
{
s32 old_off, new_off;
@ -128,7 +129,12 @@ nfp_bpf_check_stack_access(struct nfp_insn_meta *meta,
old_off = meta->ptr.off + meta->ptr.var_off.value;
new_off = reg->off + reg->var_off.value;
if (old_off == new_off)
meta->ptr_not_const |= old_off != new_off;
if (!meta->ptr_not_const)
return 0;
if (old_off % 4 == new_off % 4)
return 0;
pr_info("stack access changed location was:%d is:%d\n",
@ -151,7 +157,7 @@ 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(meta, reg);
err = nfp_bpf_check_stack_access(nfp_prog, meta, reg);
if (err)
return err;
}