Add interpreter/jit support for new sign-extension load insns
which adds a new mode (BPF_MEMSX).
Also add verifier support to recognize these insns and to
do proper verification with new insns. In verifier, besides
to deduce proper bounds for the dst_reg, probed memory access
is handled by remembering insn mode in insn->imm field so later
on proper jit insns can be emitted.
Signed-off-by: Yonghong Song <yhs@xxxxxx>
---
arch/x86/net/bpf_jit_comp.c | 32 ++++++++-
include/uapi/linux/bpf.h | 1 +
kernel/bpf/core.c | 13 ++++
kernel/bpf/verifier.c | 125 +++++++++++++++++++++++++++------
tools/include/uapi/linux/bpf.h | 1 +
5 files changed, 151 insertions(+), 21 deletions(-)
diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
index 438adb695daa..addeea95f397 100644
--- a/arch/x86/net/bpf_jit_comp.c
+++ b/arch/x86/net/bpf_jit_comp.c
@@ -779,6 +779,29 @@ static void emit_ldx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
*pprog = prog;
}
+/* LDX: dst_reg = *(s8*)(src_reg + off) */
+static void emit_ldsx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
+{
+ u8 *prog = *pprog;
+
+ switch (size) {
+ case BPF_B:
+ /* Emit 'movsx rax, byte ptr [rax + off]' */
+ EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xBE);
+ break;
+ case BPF_H:
+ /* Emit 'movsx rax, word ptr [rax + off]' */
+ EMIT3(add_2mod(0x48, src_reg, dst_reg), 0x0F, 0xBF);
+ break;
+ case BPF_W:
+ /* Emit 'movsx rax, dword ptr [rax+0x14]' */
+ EMIT2(add_2mod(0x48, src_reg, dst_reg), 0x63);
+ break;
+ }
+ emit_insn_suffix(&prog, src_reg, dst_reg, off);
+ *pprog = prog;
+}
+
/* STX: *(u8*)(dst_reg + off) = src_reg */
static void emit_stx(u8 **pprog, u32 size, u32 dst_reg, u32 src_reg, int off)
{
@@ -1370,6 +1393,9 @@ st: if (is_imm8(insn->off))
case BPF_LDX | BPF_PROBE_MEM | BPF_W:
case BPF_LDX | BPF_MEM | BPF_DW:
case BPF_LDX | BPF_PROBE_MEM | BPF_DW:
+ case BPF_LDX | BPF_MEMSX | BPF_B:
+ case BPF_LDX | BPF_MEMSX | BPF_H:
+ case BPF_LDX | BPF_MEMSX | BPF_W:
insn_off = insn->off;
if (BPF_MODE(insn->code) == BPF_PROBE_MEM) {
@@ -1415,7 +1441,11 @@ st: if (is_imm8(insn->off))
start_of_ldx = prog;
end_of_jmp[-1] = start_of_ldx - end_of_jmp;
}
- emit_ldx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn_off);
+ if ((BPF_MODE(insn->code) == BPF_PROBE_MEM && insn->imm == BPF_MEMSX) ||
+ BPF_MODE(insn->code) == BPF_MEMSX)
+ emit_ldsx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn_off);
+ else
+ emit_ldx(&prog, BPF_SIZE(insn->code), dst_reg, src_reg, insn_off);
if (BPF_MODE(insn->code) == BPF_PROBE_MEM) {
struct exception_table_entry *ex;
u8 *_insn = image + proglen + (start_of_ldx - temp);
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 600d0caebbd8..c7196302d1eb 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -19,6 +19,7 @@
/* ld/ldx fields */
#define BPF_DW 0x18 /* double word (64-bit) */
+#define BPF_MEMSX 0x80 /* load with sign extension */
#define BPF_ATOMIC 0xc0 /* atomic memory ops - op type in immediate */
#define BPF_XADD 0xc0 /* exclusive add - legacy name */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index dc85240a0134..8a1cc658789e 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -1610,6 +1610,9 @@ EXPORT_SYMBOL_GPL(__bpf_call_base);
INSN_3(LDX, MEM, H), \
INSN_3(LDX, MEM, W), \
INSN_3(LDX, MEM, DW), \
+ INSN_3(LDX, MEMSX, B), \
+ INSN_3(LDX, MEMSX, H), \
+ INSN_3(LDX, MEMSX, W), \
/* Immediate based. */ \
INSN_3(LD, IMM, DW)
@@ -1942,6 +1945,16 @@ static u64 ___bpf_prog_run(u64 *regs, const struct bpf_insn *insn)
LDST(DW, u64)
#undef LDST
+#define LDS(SIZEOP, SIZE) \
+ LDX_MEMSX_##SIZEOP: \
+ DST = *(SIZE *)(unsigned long) (SRC + insn->off); \
+ CONT;
+
+ LDS(B, s8)
+ LDS(H, s16)
+ LDS(W, s32)
+#undef LDS
+
#define ATOMIC_ALU_OP(BOP, KOP) \
case BOP: \
if (BPF_SIZE(insn->code) == BPF_W) \
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 81a93eeac7a0..fbe4ca72d4c1 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5795,6 +5795,77 @@ static void coerce_reg_to_size(struct bpf_reg_state *reg, int size)
__reg_combine_64_into_32(reg);
}
+static void set_sext64_default_val(struct bpf_reg_state *reg, int size)
+{
+ if (size == 1) {
+ reg->smin_value = reg->s32_min_value = S8_MIN;
+ reg->smax_value = reg->s32_max_value = S8_MAX;
+ } else if (size == 2) {
+ reg->smin_value = reg->s32_min_value = S16_MIN;
+ reg->smax_value = reg->s32_max_value = S16_MAX;
+ } else {
+ /* size == 4 */
+ reg->smin_value = reg->s32_min_value = S32_MIN;
+ reg->smax_value = reg->s32_max_value = S32_MAX;
+ }
+ reg->umin_value = reg->u32_min_value = 0;
+ reg->umax_value = U64_MAX;
+ reg->u32_max_value = U32_MAX;
+ reg->var_off = tnum_unknown;
+}
+
+static void coerce_reg_to_size_sx(struct bpf_reg_state *reg, int size)
+{
+ u64 top_smax_value, top_smin_value;
+ s64 init_s64_max, init_s64_min, s64_max, s64_min;
+ u64 num_bits = size * 8;
+
+ top_smax_value = ((u64)reg->smax_value >> num_bits) << num_bits;
+ top_smin_value = ((u64)reg->smin_value >> num_bits) << num_bits;
+
+ if (top_smax_value != top_smin_value)
+ goto out;
+
+ /* find the s64_min and s64_min after sign extension */
+ if (size == 1) {
+ init_s64_max = (s8)reg->smax_value;
+ init_s64_min = (s8)reg->smin_value;
+ } else if (size == 2) {
+ init_s64_max = (s16)reg->smax_value;
+ init_s64_min = (s16)reg->smin_value;
+ } else {
+ /* size == 4 */
+ init_s64_max = (s32)reg->smax_value;
+ init_s64_min = (s32)reg->smin_value;
+ }
+
+ s64_max = max(init_s64_max, init_s64_min);
+ s64_min = min(init_s64_max, init_s64_min);
+
+ if (s64_max >= 0 && s64_min >= 0) {
+ reg->smin_value = reg->s32_min_value = s64_min;
+ reg->smax_value = reg->s32_max_value = s64_max;
+ reg->umin_value = reg->u32_min_value = s64_min;
+ reg->umax_value = reg->u32_max_value = s64_max;
+ reg->var_off = tnum_range(s64_min, s64_max);
+ return;
+ }
+
+ if (s64_min < 0 && s64_max < 0) {
+ reg->smin_value = reg->s32_min_value = s64_min;
+ reg->smax_value = reg->s32_max_value = s64_max;
+ reg->umin_value = (u64)s64_max;
+ reg->umax_value = (u64)s64_min;
+ reg->u32_min_value = (u32)s64_max;
+ reg->u32_max_value = (u32)s64_min;
+ reg->var_off = tnum_range((u64)s64_max, (u64)s64_min);
+ return;
+ }
+
+out:
+ set_sext64_default_val(reg, size);
+}
+
static bool bpf_map_is_rdonly(const struct bpf_map *map)
{
/* A map is considered read-only if the following condition are true:
@@ -5815,7 +5886,8 @@ static bool bpf_map_is_rdonly(const struct bpf_map *map)
!bpf_map_write_active(map);
}
-static int bpf_map_direct_read(struct bpf_map *map, int off, int size, u64 *val)
+static int bpf_map_direct_read(struct bpf_map *map, int off, int size, u64 *val,
+ bool is_ldsx)
{
void *ptr;
u64 addr;
@@ -5828,13 +5900,13 @@ static int bpf_map_direct_read(struct bpf_map *map, int off, int size, u64 *val)
switch (size) {
case sizeof(u8):
- *val = (u64)*(u8 *)ptr;
+ *val = is_ldsx ? (s64)*(s8 *)ptr : (u64)*(u8 *)ptr;
break;
case sizeof(u16):
- *val = (u64)*(u16 *)ptr;
+ *val = is_ldsx ? (s64)*(s16 *)ptr : (u64)*(u16 *)ptr;
break;
case sizeof(u32):
- *val = (u64)*(u32 *)ptr;
+ *val = is_ldsx ? (s64)*(s32 *)ptr : (u64)*(u32 *)ptr;
break;
case sizeof(u64):
*val = *(u64 *)ptr;
@@ -6248,7 +6320,7 @@ static int check_stack_access_within_bounds(
*/
static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regno,
int off, int bpf_size, enum bpf_access_type t,
- int value_regno, bool strict_alignment_once)
+ int value_regno, bool strict_alignment_once, bool is_ldsx)
{
struct bpf_reg_state *regs = cur_regs(env);
struct bpf_reg_state *reg = regs + regno;
@@ -6309,7 +6381,7 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
u64 val = 0;
err = bpf_map_direct_read(map, map_off, size,
- &val);
+ &val, is_ldsx);
if (err)
return err;
@@ -6479,8 +6551,11 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, u32 regn
if (!err && size < BPF_REG_SIZE && value_regno >= 0 && t == BPF_READ &&
regs[value_regno].type == SCALAR_VALUE) {
- /* b/h/w load zero-extends, mark upper bits as known 0 */
- coerce_reg_to_size(®s[value_regno], size);
+ if (!is_ldsx)
+ /* b/h/w load zero-extends, mark upper bits as known 0 */
+ coerce_reg_to_size(®s[value_regno], size);
+ else
+ coerce_reg_to_size_sx(®s[value_regno], size);
}
return err;
}
@@ -6572,17 +6647,17 @@ static int check_atomic(struct bpf_verifier_env *env, int insn_idx, struct bpf_i
* case to simulate the register fill.
*/
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
- BPF_SIZE(insn->code), BPF_READ, -1, true);
+ BPF_SIZE(insn->code), BPF_READ, -1, true, false);
if (!err && load_reg >= 0)
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
BPF_SIZE(insn->code), BPF_READ, load_reg,
- true);
+ true, false);
if (err)
return err;
/* Check whether we can write into the same memory. */
err = check_mem_access(env, insn_idx, insn->dst_reg, insn->off,
- BPF_SIZE(insn->code), BPF_WRITE, -1, true);
+ BPF_SIZE(insn->code), BPF_WRITE, -1, true, false);
if (err)
return err;
@@ -6828,7 +6903,7 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, int regno,
return zero_size_allowed ? 0 : -EACCES;
return check_mem_access(env, env->insn_idx, regno, offset, BPF_B,
- atype, -1, false);
+ atype, -1, false, false);
}
fallthrough;
@@ -7200,7 +7275,7 @@ static int process_dynptr_func(struct bpf_verifier_env *env, int regno, int insn
/* we write BPF_DW bits (8 bytes) at a time */
for (i = 0; i < BPF_DYNPTR_SIZE; i += 8) {
err = check_mem_access(env, insn_idx, regno,
- i, BPF_DW, BPF_WRITE, -1, false);
+ i, BPF_DW, BPF_WRITE, -1, false, false);
if (err)
return err;
}
@@ -7293,7 +7368,7 @@ static int process_iter_arg(struct bpf_verifier_env *env, int regno, int insn_id
for (i = 0; i < nr_slots * 8; i += BPF_REG_SIZE) {
err = check_mem_access(env, insn_idx, regno,
- i, BPF_DW, BPF_WRITE, -1, false);
+ i, BPF_DW, BPF_WRITE, -1, false, false);
if (err)
return err;
}
@@ -9437,7 +9512,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
*/
for (i = 0; i < meta.access_size; i++) {
err = check_mem_access(env, insn_idx, meta.regno, i, BPF_B,
- BPF_WRITE, -1, false);
+ BPF_WRITE, -1, false, false);
if (err)
return err;
}
@@ -16315,7 +16390,8 @@ static int do_check(struct bpf_verifier_env *env)
*/
err = check_mem_access(env, env->insn_idx, insn->src_reg,
insn->off, BPF_SIZE(insn->code),
- BPF_READ, insn->dst_reg, false);
+ BPF_READ, insn->dst_reg, false,
+ BPF_MODE(insn->code) == BPF_MEMSX);
if (err)
return err;
@@ -16352,7 +16428,7 @@ static int do_check(struct bpf_verifier_env *env)
/* check that memory (dst_reg + off) is writeable */
err = check_mem_access(env, env->insn_idx, insn->dst_reg,
insn->off, BPF_SIZE(insn->code),
- BPF_WRITE, insn->src_reg, false);
+ BPF_WRITE, insn->src_reg, false, false);
if (err)
return err;
@@ -16377,7 +16453,7 @@ static int do_check(struct bpf_verifier_env *env)
/* check that memory (dst_reg + off) is writeable */
err = check_mem_access(env, env->insn_idx, insn->dst_reg,
insn->off, BPF_SIZE(insn->code),
- BPF_WRITE, -1, false);
+ BPF_WRITE, -1, false, false);
if (err)
return err;
@@ -16805,7 +16881,8 @@ static int resolve_pseudo_ldimm64(struct bpf_verifier_env *env)
for (i = 0; i < insn_cnt; i++, insn++) {
if (BPF_CLASS(insn->code) == BPF_LDX &&
- (BPF_MODE(insn->code) != BPF_MEM || insn->imm != 0)) {
+ ((BPF_MODE(insn->code) != BPF_MEM && BPF_MODE(insn->code) != BPF_MEMSX) ||
+ insn->imm != 0)) {
verbose(env, "BPF_LDX uses reserved fields\n");
return -EINVAL;
}
@@ -17503,7 +17580,10 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
if (insn->code == (BPF_LDX | BPF_MEM | BPF_B) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_H) ||
insn->code == (BPF_LDX | BPF_MEM | BPF_W) ||
- insn->code == (BPF_LDX | BPF_MEM | BPF_DW)) {
+ insn->code == (BPF_LDX | BPF_MEM | BPF_DW) ||
+ insn->code == (BPF_LDX | BPF_MEMSX | BPF_B) ||
+ insn->code == (BPF_LDX | BPF_MEMSX | BPF_H) ||
+ insn->code == (BPF_LDX | BPF_MEMSX | BPF_W)) {
type = BPF_READ;
} else if (insn->code == (BPF_STX | BPF_MEM | BPF_B) ||
insn->code == (BPF_STX | BPF_MEM | BPF_H) ||
@@ -17562,6 +17642,11 @@ static int convert_ctx_accesses(struct bpf_verifier_env *env)
*/
case PTR_TO_BTF_ID | MEM_ALLOC | PTR_UNTRUSTED:
if (type == BPF_READ) {
+ /* it is hard to differentiate that the
+ * BPF_PROBE_MEM is for BPF_MEM or BPF_MEMSX,
+ * let us use insn->imm to remember it.
+ */
+ insn->imm = BPF_MODE(insn->code);
insn->code = BPF_LDX | BPF_PROBE_MEM |
BPF_SIZE((insn)->code);
env->prog->aux->num_exentries++;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 600d0caebbd8..c7196302d1eb 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -19,6 +19,7 @@
/* ld/ldx fields */
#define BPF_DW 0x18 /* double word (64-bit) */
+#define BPF_MEMSX 0x80 /* load with sign extension */
#define BPF_ATOMIC 0xc0 /* atomic memory ops - op type in immediate */
#define BPF_XADD 0xc0 /* exclusive add - legacy name */
--
2.34.1
