nfp: bpf: support stack accesses via non-constant pointers
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>
diff --git a/drivers/net/ethernet/netronome/nfp/bpf/jit.c b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
index 5105b92..d84f00b 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/jit.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/jit.c
@@ -832,8 +832,8 @@
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 @@
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 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 @@
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 @@
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
diff --git a/drivers/net/ethernet/netronome/nfp/bpf/main.h b/drivers/net/ethernet/netronome/nfp/bpf/main.h
index d4f144a..86edc06 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/main.h
+++ b/drivers/net/ethernet/netronome/nfp/bpf/main.h
@@ -101,6 +101,7 @@
* 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 @@
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;
diff --git a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
index 633db3e..3d3dcac 100644
--- a/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
+++ b/drivers/net/ethernet/netronome/nfp/bpf/verifier.c
@@ -112,7 +112,8 @@
}
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 @@
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 @@
}
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;
}