From: Andrii Nakryiko <andrii@kernel.org>
To: <bpf@vger.kernel.org>, <ast@kernel.org>, <daniel@iogearbox.net>,
<martin.lau@kernel.org>
Cc: <andrii@kernel.org>, <kernel-team@meta.com>
Subject: [PATCH bpf-next 7/8] bpf: smarter verifier log number printing logic
Date: Fri, 10 Nov 2023 08:10:56 -0800 [thread overview]
Message-ID: <20231110161057.1943534-8-andrii@kernel.org> (raw)
In-Reply-To: <20231110161057.1943534-1-andrii@kernel.org>
Instead of always printing numbers as either decimals (and in some
cases, like for "imm=%llx", in hexadecimals), decide the form based on
actual values. For numbers in a reasonably small range (currently,
[0, U16_MAX] for unsigned values, and [S16_MIN, S16_MAX] for signed ones),
emit them as decimals. In all other cases, even for signed values,
emit them in hexadecimals.
For large values hex form is often times way more useful: it's easier to
see an exact difference between 0xffffffff80000000 and 0xffffffff7fffffff,
than between 18446744071562067966 and 18446744071562067967, as one
particular example.
Small values representing small pointer offsets or application
constants, on the other hand, are way more useful to be represented in
decimal notation.
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
---
kernel/bpf/log.c | 67 +++++++++++++++++--
.../selftests/bpf/progs/exceptions_assert.c | 32 ++++-----
2 files changed, 76 insertions(+), 23 deletions(-)
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index 20b4f81087da..2f4d055849a4 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -509,10 +509,52 @@ static void print_liveness(struct bpf_verifier_env *env,
verbose(env, "D");
}
+#define UNUM_MAX_DECIMAL U16_MAX
+#define SNUM_MAX_DECIMAL S16_MAX
+#define SNUM_MIN_DECIMAL S16_MIN
+
+static bool is_unum_decimal(u64 num)
+{
+ return num <= UNUM_MAX_DECIMAL;
+}
+
+static bool is_snum_decimal(s64 num)
+{
+ return num >= SNUM_MIN_DECIMAL && num <= SNUM_MAX_DECIMAL;
+}
+
+static void verbose_unum(struct bpf_verifier_env *env, u64 num)
+{
+ if (is_unum_decimal(num))
+ verbose(env, "%llu", num);
+ else
+ verbose(env, "%#llx", num);
+}
+
+static void verbose_snum(struct bpf_verifier_env *env, s64 num)
+{
+ if (is_snum_decimal(num))
+ verbose(env, "%lld", num);
+ else
+ verbose(env, "%#llx", num);
+}
+
static void print_scalar_ranges(struct bpf_verifier_env *env,
const struct bpf_reg_state *reg,
const char **sep)
{
+ /* For signed ranges, we want to unify 64-bit and 32-bit values in the
+ * output as much as possible, but there is a bit of a complication.
+ * If we choose to print values as decimals, this is natural to do,
+ * because negative 64-bit and 32-bit values >= -S32_MIN have the same
+ * representation due to sign extension. But if we choose to print
+ * them in hex format (see is_snum_decimal()), then sign extension is
+ * misleading.
+ * E.g., smin=-2 and smin32=-2 are exactly the same in decimal, but in
+ * hex they will be smin=0xfffffffffffffffe and smin32=0xfffffffe, two
+ * very different numbers.
+ * So we avoid sign extension if we choose to print values in hex.
+ */
struct {
const char *name;
u64 val;
@@ -522,8 +564,14 @@ static void print_scalar_ranges(struct bpf_verifier_env *env,
{"smax", reg->smax_value, reg->smax_value == S64_MAX},
{"umin", reg->umin_value, reg->umin_value == 0},
{"umax", reg->umax_value, reg->umax_value == U64_MAX},
- {"smin32", (s64)reg->s32_min_value, reg->s32_min_value == S32_MIN},
- {"smax32", (s64)reg->s32_max_value, reg->s32_max_value == S32_MAX},
+ {"smin32",
+ is_snum_decimal((s64)reg->s32_min_value)
+ ? (s64)reg->s32_min_value
+ : (u32)reg->s32_min_value, reg->s32_min_value == S32_MIN},
+ {"smax32",
+ is_snum_decimal((s64)reg->s32_max_value)
+ ? (s64)reg->s32_max_value
+ : (u32)reg->s32_max_value, reg->s32_max_value == S32_MAX},
{"umin32", reg->u32_min_value, reg->u32_min_value == 0},
{"umax32", reg->u32_max_value, reg->u32_max_value == U32_MAX},
}, *m1, *m2, *mend = &minmaxs[ARRAY_SIZE(minmaxs)];
@@ -549,7 +597,10 @@ static void print_scalar_ranges(struct bpf_verifier_env *env,
verbose(env, "%s=", m2->name);
}
- verbose(env, m1->name[0] == 's' ? "%lld" : "%llu", m1->val);
+ if (m1->name[0] == 's')
+ verbose_snum(env, m1->val);
+ else
+ verbose_unum(env, m1->val);
}
}
@@ -576,14 +627,14 @@ static void print_reg_state(struct bpf_verifier_env *env, const struct bpf_reg_s
tnum_is_const(reg->var_off)) {
/* reg->off should be 0 for SCALAR_VALUE */
verbose(env, "%s", t == SCALAR_VALUE ? "" : reg_type_str(env, t));
- verbose(env, "%lld", reg->var_off.value + reg->off);
+ verbose_snum(env, reg->var_off.value + reg->off);
return;
}
/*
* _a stands for append, was shortened to avoid multiline statements below.
* This macro is used to output a comma separated list of attributes.
*/
-#define verbose_a(fmt, ...) ({ verbose(env, "%s" fmt, sep, __VA_ARGS__); sep = ","; })
+#define verbose_a(fmt, ...) ({ verbose(env, "%s" fmt, sep, ##__VA_ARGS__); sep = ","; })
verbose(env, "%s", reg_type_str(env, t));
if (base_type(t) == PTR_TO_BTF_ID)
@@ -608,8 +659,10 @@ static void print_reg_state(struct bpf_verifier_env *env, const struct bpf_reg_s
verbose_a("r=%d", reg->range);
if (tnum_is_const(reg->var_off)) {
/* a pointer register with fixed offset */
- if (reg->var_off.value)
- verbose_a("imm=%llx", reg->var_off.value);
+ if (reg->var_off.value) {
+ verbose_a("imm=");
+ verbose_snum(env, reg->var_off.value);
+ }
} else {
print_scalar_ranges(env, reg, &sep);
if (!tnum_is_unknown(reg->var_off)) {
diff --git a/tools/testing/selftests/bpf/progs/exceptions_assert.c b/tools/testing/selftests/bpf/progs/exceptions_assert.c
index 26f7d67432cc..49efaed143fc 100644
--- a/tools/testing/selftests/bpf/progs/exceptions_assert.c
+++ b/tools/testing/selftests/bpf/progs/exceptions_assert.c
@@ -18,48 +18,48 @@
return *(u64 *)num; \
}
-__msg(": R0_w=-2147483648 R10=fp0")
+__msg(": R0_w=0xffffffff80000000 R10=fp0")
check_assert(s64, eq, int_min, INT_MIN);
-__msg(": R0_w=2147483647 R10=fp0")
+__msg(": R0_w=0x7fffffff R10=fp0")
check_assert(s64, eq, int_max, INT_MAX);
__msg(": R0_w=0 R10=fp0")
check_assert(s64, eq, zero, 0);
-__msg(": R0_w=-9223372036854775808 R1_w=-9223372036854775808 R10=fp0")
+__msg(": R0_w=0x8000000000000000 R1_w=0x8000000000000000 R10=fp0")
check_assert(s64, eq, llong_min, LLONG_MIN);
-__msg(": R0_w=9223372036854775807 R1_w=9223372036854775807 R10=fp0")
+__msg(": R0_w=0x7fffffffffffffff R1_w=0x7fffffffffffffff R10=fp0")
check_assert(s64, eq, llong_max, LLONG_MAX);
-__msg(": R0_w=scalar(smax=2147483646) R10=fp0")
+__msg(": R0_w=scalar(smax=0x7ffffffe) R10=fp0")
check_assert(s64, lt, pos, INT_MAX);
-__msg(": R0_w=scalar(smax=-1,umin=9223372036854775808,var_off=(0x8000000000000000; 0x7fffffffffffffff))")
+__msg(": R0_w=scalar(smax=-1,umin=0x8000000000000000,var_off=(0x8000000000000000; 0x7fffffffffffffff))")
check_assert(s64, lt, zero, 0);
-__msg(": R0_w=scalar(smax=-2147483649,umin=9223372036854775808,umax=18446744071562067967,var_off=(0x8000000000000000; 0x7fffffffffffffff))")
+__msg(": R0_w=scalar(smax=0xffffffff7fffffff,umin=0x8000000000000000,umax=0xffffffff7fffffff,var_off=(0x8000000000000000; 0x7fffffffffffffff))")
check_assert(s64, lt, neg, INT_MIN);
-__msg(": R0_w=scalar(smax=2147483647) R10=fp0")
+__msg(": R0_w=scalar(smax=0x7fffffff) R10=fp0")
check_assert(s64, le, pos, INT_MAX);
__msg(": R0_w=scalar(smax=0) R10=fp0")
check_assert(s64, le, zero, 0);
-__msg(": R0_w=scalar(smax=-2147483648,umin=9223372036854775808,umax=18446744071562067968,var_off=(0x8000000000000000; 0x7fffffffffffffff))")
+__msg(": R0_w=scalar(smax=0xffffffff80000000,umin=0x8000000000000000,umax=0xffffffff80000000,var_off=(0x8000000000000000; 0x7fffffffffffffff))")
check_assert(s64, le, neg, INT_MIN);
-__msg(": R0_w=scalar(smin=umin=2147483648,umax=9223372036854775807,var_off=(0x0; 0x7fffffffffffffff))")
+__msg(": R0_w=scalar(smin=umin=0x80000000,umax=0x7fffffffffffffff,var_off=(0x0; 0x7fffffffffffffff))")
check_assert(s64, gt, pos, INT_MAX);
-__msg(": R0_w=scalar(smin=umin=1,umax=9223372036854775807,var_off=(0x0; 0x7fffffffffffffff))")
+__msg(": R0_w=scalar(smin=umin=1,umax=0x7fffffffffffffff,var_off=(0x0; 0x7fffffffffffffff))")
check_assert(s64, gt, zero, 0);
-__msg(": R0_w=scalar(smin=-2147483647) R10=fp0")
+__msg(": R0_w=scalar(smin=0xffffffff80000001) R10=fp0")
check_assert(s64, gt, neg, INT_MIN);
-__msg(": R0_w=scalar(smin=umin=2147483647,umax=9223372036854775807,var_off=(0x0; 0x7fffffffffffffff))")
+__msg(": R0_w=scalar(smin=umin=0x7fffffff,umax=0x7fffffffffffffff,var_off=(0x0; 0x7fffffffffffffff))")
check_assert(s64, ge, pos, INT_MAX);
-__msg(": R0_w=scalar(smin=0,umax=9223372036854775807,var_off=(0x0; 0x7fffffffffffffff)) R10=fp0")
+__msg(": R0_w=scalar(smin=0,umax=0x7fffffffffffffff,var_off=(0x0; 0x7fffffffffffffff)) R10=fp0")
check_assert(s64, ge, zero, 0);
-__msg(": R0_w=scalar(smin=-2147483648) R10=fp0")
+__msg(": R0_w=scalar(smin=0xffffffff80000000) R10=fp0")
check_assert(s64, ge, neg, INT_MIN);
SEC("?tc")
__log_level(2) __failure
-__msg(": R0=0 R1=ctx() R2=scalar(smin=smin32=-2147483646,smax=smax32=2147483645) R10=fp0")
+__msg(": R0=0 R1=ctx() R2=scalar(smin=0xffffffff80000002,smax=smax32=0x7ffffffd,smin32=0x80000002) R10=fp0")
int check_assert_range_s64(struct __sk_buff *ctx)
{
struct bpf_sock *sk = ctx->sk;
--
2.34.1
next prev parent reply other threads:[~2023-11-10 16:11 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-10 16:10 [PATCH bpf-next 0/8] BPF verifier log improvements Andrii Nakryiko
2023-11-10 16:10 ` [PATCH bpf-next 1/8] bpf: move verbose_linfo() into kernel/bpf/log.c Andrii Nakryiko
2023-11-10 16:10 ` [PATCH bpf-next 2/8] bpf: move verifier state printing code to kernel/bpf/log.c Andrii Nakryiko
2023-11-10 17:37 ` Stanislav Fomichev
2023-11-10 17:49 ` Andrii Nakryiko
2023-11-10 16:10 ` [PATCH bpf-next 3/8] bpf: extract register state printing Andrii Nakryiko
2023-11-10 16:10 ` [PATCH bpf-next 4/8] bpf: print spilled register state in stack slot Andrii Nakryiko
2023-11-11 0:31 ` Eduard Zingerman
2023-11-10 16:10 ` [PATCH bpf-next 5/8] bpf: emit map name in register state if applicable and available Andrii Nakryiko
2023-11-10 16:10 ` [PATCH bpf-next 6/8] bpf: omit default off=0 and imm=0 in register state log Andrii Nakryiko
2023-11-10 16:10 ` Andrii Nakryiko [this message]
2023-11-11 0:51 ` [PATCH bpf-next 7/8] bpf: smarter verifier log number printing logic Eduard Zingerman
2023-11-11 6:31 ` Andrii Nakryiko
2023-11-10 16:10 ` [PATCH bpf-next 8/8] bpf: emit frameno for PTR_TO_STACK regs if it differs from current one Andrii Nakryiko
2023-11-10 18:50 ` [PATCH bpf-next 0/8] BPF verifier log improvements Stanislav Fomichev
2023-11-10 19:13 ` Andrii Nakryiko
2023-11-11 0:57 ` Eduard Zingerman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20231110161057.1943534-8-andrii@kernel.org \
--to=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=kernel-team@meta.com \
--cc=martin.lau@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox