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bpf: print spilled register state in stack slot

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Print the same register state representation when printing stack state,
as we do for normal registers. Note that if stack slot contains
subregister spill (1, 2, or 4 byte long), we'll still emit "m0?" mask
for those bytes that are not part of spilled register.

While means we can get something like fp-8=0000scalar() for a 4-byte
spill with other 4 bytes still being STACK_ZERO.

Some example before and after, taken from the log of
pyperf_subprogs.bpf.o:

49: (7b) *(u64 *)(r10 -256) = r1      ; frame1: R1_w=ctx(off=0,imm=0) R10=fp0 fp-256_w=ctx
49: (7b) *(u64 *)(r10 -256) = r1      ; frame1: R1_w=ctx(off=0,imm=0) R10=fp0 fp-256_w=ctx(off=0,imm=0)

150: (7b) *(u64 *)(r10 -264) = r0     ; frame1: R0_w=map_value_or_null(id=6,off=0,ks=192,vs=4,imm=0) R10=fp0 fp-264_w=map_value_or_null
150: (7b) *(u64 *)(r10 -264) = r0     ; frame1: R0_w=map_value_or_null(id=6,off=0,ks=192,vs=4,imm=0) R10=fp0 fp-264_w=map_value_or_null(id=6,off=0,ks=192,vs=4,imm=0)

5192: (61) r1 = *(u32 *)(r10 -272)    ; frame1: R1_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=15,var_off=(0x0; 0xf)) R10=fp0 fp-272=
5192: (61) r1 = *(u32 *)(r10 -272)    ; frame1: R1_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=15,var_off=(0x0; 0xf)) R10=fp0 fp-272=????scalar(smin=smin32=0,smax=umax=smax32=umax32=15,var_off=(0x0; 0xf))

While at it, do a few other simple clean ups:
  - skip slot if it's not scratched before detecting whether it's valid;
  - move taking spilled_reg pointer outside of switch (only DYNPTR has
    to adjust that to get to the "main" slot);
  - don't recalculate types_buf second time for MISC/ZERO/default case.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231118034623.3320920-5-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrii Nakryiko 2023-11-17 19:46:19 -08:00 committed by Alexei Starovoitov
parent 009f5465be
commit 67d43dfbb4
1 changed files with 17 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
kernel/bpf/log.c
View File

@ -618,7 +618,6 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_func_st
bool print_all)
{
const struct bpf_reg_state *reg;
enum bpf_reg_type t;
int i;
if (state->frameno)
@ -637,32 +636,38 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_func_st
for (i = 0; i < state->allocated_stack / BPF_REG_SIZE; i++) {
char types_buf[BPF_REG_SIZE + 1];
bool valid = false;
u8 slot_type;
int j;
if (!print_all && !stack_slot_scratched(env, i))
continue;
for (j = 0; j < BPF_REG_SIZE; j++) {
if (state->stack[i].slot_type[j] != STACK_INVALID)
slot_type = state->stack[i].slot_type[j];
if (slot_type != STACK_INVALID)
valid = true;
types_buf[j] = slot_type_char[state->stack[i].slot_type[j]];
types_buf[j] = slot_type_char[slot_type];
}
types_buf[BPF_REG_SIZE] = 0;
if (!valid)
continue;
if (!print_all && !stack_slot_scratched(env, i))
continue;
reg = &state->stack[i].spilled_ptr;
switch (state->stack[i].slot_type[BPF_REG_SIZE - 1]) {
case STACK_SPILL:
reg = &state->stack[i].spilled_ptr;
t = reg->type;
/* print MISC/ZERO/INVALID slots above subreg spill */
for (j = 0; j < BPF_REG_SIZE; j++)
if (state->stack[i].slot_type[j] == STACK_SPILL)
break;
types_buf[j] = '\0';
verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE);
print_liveness(env, reg->live);
verbose(env, "=%s", t == SCALAR_VALUE ? "" : reg_type_str(env, t));
if (t == SCALAR_VALUE && reg->precise)
verbose(env, "P");
if (t == SCALAR_VALUE && tnum_is_const(reg->var_off))
verbose(env, "%lld", reg->var_off.value + reg->off);
verbose(env, "=%s", types_buf);
print_reg_state(env, reg);
break;
case STACK_DYNPTR:
/* skip to main dynptr slot */
i += BPF_DYNPTR_NR_SLOTS - 1;
reg = &state->stack[i].spilled_ptr;
@ -674,7 +679,6 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_func_st
break;
case STACK_ITER:
/* only main slot has ref_obj_id set; skip others */
reg = &state->stack[i].spilled_ptr;
if (!reg->ref_obj_id)
continue;
@ -688,12 +692,6 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_func_st
case STACK_MISC:
case STACK_ZERO:
default:
reg = &state->stack[i].spilled_ptr;
for (j = 0; j < BPF_REG_SIZE; j++)
types_buf[j] = slot_type_char[state->stack[i].slot_type[j]];
types_buf[BPF_REG_SIZE] = 0;
verbose(env, " fp%d", (-i - 1) * BPF_REG_SIZE);
print_liveness(env, reg->live);
verbose(env, "=%s", types_buf);