bpf: simplify tnum output if a fully known constant

Emit tnum representation as just a constant if all bits are known.
Use decimal-vs-hex logic to determine exact format of emitted
constant value, just like it's done for register range values.
For that move tnum_strn() to kernel/bpf/log.c to reuse decimal-vs-hex
determination logic and constants.

Acked-by: Shung-Hsi Yu <shung-hsi.yu@suse.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231202175705.885270-12-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

kernel/bpf/log.c

@@ -539,6 +539,19 @@ static void verbose_snum(struct bpf_verifier_env *env, s64 num)
 		verbose(env, "%#llx", num);
 }
 
+int tnum_strn(char *str, size_t size, struct tnum a)
+{
+	/* print as a constant, if tnum is fully known */
+	if (a.mask == 0) {
+		if (is_unum_decimal(a.value))
+			return snprintf(str, size, "%llu", a.value);
+		else
+			return snprintf(str, size, "%#llx", a.value);
+	}
+	return snprintf(str, size, "(%#llx; %#llx)", a.value, a.mask);
+}
+EXPORT_SYMBOL_GPL(tnum_strn);
+
 static void print_scalar_ranges(struct bpf_verifier_env *env,
 				const struct bpf_reg_state *reg,
 				const char **sep)

kernel/bpf/tnum.c

@@ -172,12 +172,6 @@ bool tnum_in(struct tnum a, struct tnum b)
 	return a.value == b.value;
 }
 
-int tnum_strn(char *str, size_t size, struct tnum a)
-{
-	return snprintf(str, size, "(%#llx; %#llx)", a.value, a.mask);
-}
-EXPORT_SYMBOL_GPL(tnum_strn);
-
 int tnum_sbin(char *str, size_t size, struct tnum a)
 {
 	size_t n;

tools/testing/selftests/bpf/progs/verifier_direct_packet_access.c

@@ -411,7 +411,7 @@ l0_%=:	r0 = 0;						\
 
 SEC("tc")
 __description("direct packet access: test17 (pruning, alignment)")
-__failure __msg("misaligned packet access off 2+(0x0; 0x0)+15+-4 size 4")
+__failure __msg("misaligned packet access off 2+0+15+-4 size 4")
 __flag(BPF_F_STRICT_ALIGNMENT)
 __naked void packet_access_test17_pruning_alignment(void)
 {

tools/testing/selftests/bpf/progs/verifier_int_ptr.c

@@ -67,7 +67,7 @@ __naked void ptr_to_long_half_uninitialized(void)
 
 SEC("cgroup/sysctl")
 __description("ARG_PTR_TO_LONG misaligned")
-__failure __msg("misaligned stack access off (0x0; 0x0)+-20+0 size 8")
+__failure __msg("misaligned stack access off 0+-20+0 size 8")
 __naked void arg_ptr_to_long_misaligned(void)
 {
 	asm volatile ("					\

tools/testing/selftests/bpf/progs/verifier_stack_ptr.c

@@ -37,7 +37,7 @@ __naked void ptr_to_stack_store_load(void)
 
 SEC("socket")
 __description("PTR_TO_STACK store/load - bad alignment on off")
-__failure __msg("misaligned stack access off (0x0; 0x0)+-8+2 size 8")
+__failure __msg("misaligned stack access off 0+-8+2 size 8")
 __failure_unpriv
 __naked void load_bad_alignment_on_off(void)
 {
@@ -53,7 +53,7 @@ __naked void load_bad_alignment_on_off(void)
 
 SEC("socket")
 __description("PTR_TO_STACK store/load - bad alignment on reg")
-__failure __msg("misaligned stack access off (0x0; 0x0)+-10+8 size 8")
+__failure __msg("misaligned stack access off 0+-10+8 size 8")
 __failure_unpriv
 __naked void load_bad_alignment_on_reg(void)
 {