selftests/bpf: Add test for conditional jumps on same scalar register

Add test cases to verify the correctness of the BPF verifier's branch analysis
when conditional jumps are performed on the same scalar register. And make sure
that JGT does not trigger verifier BUG.

Signed-off-by: KaFai Wan <kafai.wan@linux.dev>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20251103063108.1111764-3-kafai.wan@linux.dev
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/tools/testing/selftests/bpf/progs/verifier_bounds.c b/tools/testing/selftests/bpf/progs/verifier_bounds.c
index 0a72e0228ea9a24e614cdc06f96fe90a63ceb9cf..411a18437d7eab4e985309375312cef480f4b7f1 100644 (file)
--- a/tools/testing/selftests/bpf/progs/verifier_bounds.c
+++ b/tools/testing/selftests/bpf/progs/verifier_bounds.c
@@ -1709,4 +1709,158 @@ __naked void jeq_disagreeing_tnums(void *ctx)
        : __clobber_all);
 }
 
+SEC("socket")
+__description("conditional jump on same register, branch taken")
+__not_msg("20: (b7) r0 = 1 {{.*}} R0=1")
+__success __log_level(2)
+__retval(0) __flag(BPF_F_TEST_REG_INVARIANTS)
+__naked void condition_jump_on_same_register(void *ctx)
+{
+       asm volatile("                  \
+       call %[bpf_get_prandom_u32];    \
+       w8 = 0x80000000;                \
+       r0 &= r8;                       \
+       if r0 == r0 goto +1;            \
+       goto l1_%=;                     \
+       if r0 >= r0 goto +1;            \
+       goto l1_%=;                     \
+       if r0 s>= r0 goto +1;           \
+       goto l1_%=;                     \
+       if r0 <= r0 goto +1;            \
+       goto l1_%=;                     \
+       if r0 s<= r0 goto +1;           \
+       goto l1_%=;                     \
+       if r0 != r0 goto l1_%=;         \
+       if r0 >  r0 goto l1_%=;         \
+       if r0 s> r0 goto l1_%=;         \
+       if r0 <  r0 goto l1_%=;         \
+       if r0 s< r0 goto l1_%=;         \
+l0_%=: r0 = 0;                         \
+       exit;                           \
+l1_%=: r0 = 1;                         \
+       exit;                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
+SEC("socket")
+__description("jset on same register, constant value branch taken")
+__not_msg("7: (b7) r0 = 1 {{.*}} R0=1")
+__success __log_level(2)
+__retval(0) __flag(BPF_F_TEST_REG_INVARIANTS)
+__naked void jset_on_same_register_1(void *ctx)
+{
+       asm volatile("                  \
+       r0 = 0;                         \
+       if r0 & r0 goto l1_%=;          \
+       r0 = 1;                         \
+       if r0 & r0 goto +1;             \
+       goto l1_%=;                     \
+l0_%=: r0 = 0;                         \
+       exit;                           \
+l1_%=: r0 = 1;                         \
+       exit;                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
+SEC("socket")
+__description("jset on same register, scalar value branch taken")
+__not_msg("12: (b7) r0 = 1 {{.*}} R0=1")
+__success __log_level(2)
+__retval(0) __flag(BPF_F_TEST_REG_INVARIANTS)
+__naked void jset_on_same_register_2(void *ctx)
+{
+       asm volatile("                  \
+       /* range [1;2] */               \
+       call %[bpf_get_prandom_u32];    \
+       r0 &= 0x1;                      \
+       r0 += 1;                        \
+       if r0 & r0 goto +1;             \
+       goto l1_%=;                     \
+       /* range [-2;-1] */             \
+       call %[bpf_get_prandom_u32];    \
+       r0 &= 0x1;                      \
+       r0 -= 2;                        \
+       if r0 & r0 goto +1;             \
+       goto l1_%=;                     \
+l0_%=: r0 = 0;                         \
+       exit;                           \
+l1_%=: r0 = 1;                         \
+       exit;                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
+SEC("socket")
+__description("jset on same register, scalar value unknown branch 1")
+__msg("3: (b7) r0 = 0 {{.*}} R0=0")
+__msg("5: (b7) r0 = 1 {{.*}} R0=1")
+__success __log_level(2)
+__flag(BPF_F_TEST_REG_INVARIANTS)
+__naked void jset_on_same_register_3(void *ctx)
+{
+       asm volatile("                  \
+       /* range [0;1] */               \
+       call %[bpf_get_prandom_u32];    \
+       r0 &= 0x1;                      \
+       if r0 & r0 goto l1_%=;          \
+l0_%=: r0 = 0;                         \
+       exit;                           \
+l1_%=: r0 = 1;                         \
+       exit;                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
+SEC("socket")
+__description("jset on same register, scalar value unknown branch 2")
+__msg("4: (b7) r0 = 0 {{.*}} R0=0")
+__msg("6: (b7) r0 = 1 {{.*}} R0=1")
+__success __log_level(2)
+__flag(BPF_F_TEST_REG_INVARIANTS)
+__naked void jset_on_same_register_4(void *ctx)
+{
+       asm volatile("                  \
+       /* range [-1;0] */              \
+       call %[bpf_get_prandom_u32];    \
+       r0 &= 0x1;                      \
+       r0 -= 1;                        \
+       if r0 & r0 goto l1_%=;          \
+l0_%=: r0 = 0;                         \
+       exit;                           \
+l1_%=: r0 = 1;                         \
+       exit;                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
+SEC("socket")
+__description("jset on same register, scalar value unknown branch 3")
+__msg("4: (b7) r0 = 0 {{.*}} R0=0")
+__msg("6: (b7) r0 = 1 {{.*}} R0=1")
+__success __log_level(2)
+__flag(BPF_F_TEST_REG_INVARIANTS)
+__naked void jset_on_same_register_5(void *ctx)
+{
+       asm volatile("                  \
+       /* range [-1;1] */              \
+       call %[bpf_get_prandom_u32];    \
+       r0 &= 0x2;                      \
+       r0 -= 1;                        \
+       if r0 & r0 goto l1_%=;          \
+l0_%=: r0 = 0;                         \
+       exit;                           \
+l1_%=: r0 = 1;                         \
+       exit;                           \
+"      :
+       : __imm(bpf_get_prandom_u32)
+       : __clobber_all);
+}
+
 char _license[] SEC("license") = "GPL";