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| author | Paul Chaignon <paul.chaignon@gmail.com> | 2025-08-20 15:19:13 +0200 |
|---|---|---|
| committer | Daniel Borkmann <daniel@iogearbox.net> | 2025-08-22 18:12:34 +0200 |
| commit | 0780f54ab129b28e2b29689c95ad579a9db04fab (patch) | |
| tree | 45e85b94222e63bdc2176706e901be239fd37966 | |
| parent | f41345f47fb267a9c95ca710c33448f8d0d81d83 (diff) | |
| download | linux-0780f54ab129b28e2b29689c95ad579a9db04fab.tar.gz linux-0780f54ab129b28e2b29689c95ad579a9db04fab.tar.bz2 linux-0780f54ab129b28e2b29689c95ad579a9db04fab.zip | |
selftests/bpf: Tests for is_scalar_branch_taken tnum logic
This patch adds tests for the new jeq and jne logic in
is_scalar_branch_taken. The following shows the first test failing
before the previous patch is applied. Once the previous patch is
applied, the verifier can use the tnum values to deduce that instruction
7 is dead code.
0: call bpf_get_prandom_u32#7 ; R0_w=scalar()
1: w0 = w0 ; R0_w=scalar(smin=0,smax=umax=0xffffffff,var_off=(0x0; 0xffffffff))
2: r0 >>= 30 ; R0_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=3,var_off=(0x0; 0x3))
3: r0 <<= 30 ; R0_w=scalar(smin=0,smax=umax=umax32=0xc0000000,smax32=0x40000000,var_off=(0x0; 0xc0000000))
4: r1 = r0 ; R0_w=scalar(id=1,smin=0,smax=umax=umax32=0xc0000000,smax32=0x40000000,var_off=(0x0; 0xc0000000)) R1_w=scalar(id=1,smin=0,smax=umax=umax32=0xc0000000,smax32=0x40000000,var_off=(0x0; 0xc0000000))
5: r1 += 1024 ; R1_w=scalar(smin=umin=umin32=1024,smax=umax=umax32=0xc0000400,smin32=0x80000400,smax32=0x40000400,var_off=(0x400; 0xc0000000))
6: if r1 != r0 goto pc+1 ; R0_w=scalar(id=1,smin=umin=umin32=1024,smax=umax=umax32=0xc0000000,smin32=0x80000400,smax32=0x40000000,var_off=(0x400; 0xc0000000)) R1_w=scalar(smin=umin=umin32=1024,smax=umax=umax32=0xc0000000,smin32=0x80000400,smax32=0x40000400,var_off=(0x400; 0xc0000000))
7: r10 = 0
frame pointer is read only
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/bpf/550004f935e2553bdb2fb1f09cbde7d0452112d0.1755694148.git.paul.chaignon@gmail.com
| -rw-r--r-- | tools/testing/selftests/bpf/progs/verifier_bounds.c | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/tools/testing/selftests/bpf/progs/verifier_bounds.c b/tools/testing/selftests/bpf/progs/verifier_bounds.c index 87a2c60d86e6..fbccc20555f4 100644 --- a/tools/testing/selftests/bpf/progs/verifier_bounds.c +++ b/tools/testing/selftests/bpf/progs/verifier_bounds.c @@ -1668,4 +1668,45 @@ l0_%=: r0 = 0; \ : __clobber_all); } +SEC("socket") +__description("dead jne branch due to disagreeing tnums") +__success __log_level(2) +__naked void jne_disagreeing_tnums(void *ctx) +{ + asm volatile(" \ + call %[bpf_get_prandom_u32]; \ + w0 = w0; \ + r0 >>= 30; \ + r0 <<= 30; \ + r1 = r0; \ + r1 += 1024; \ + if r1 != r0 goto +1; \ + r10 = 0; \ + exit; \ +" : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + +SEC("socket") +__description("dead jeq branch due to disagreeing tnums") +__success __log_level(2) +__naked void jeq_disagreeing_tnums(void *ctx) +{ + asm volatile(" \ + call %[bpf_get_prandom_u32]; \ + w0 = w0; \ + r0 >>= 30; \ + r0 <<= 30; \ + r1 = r0; \ + r1 += 1024; \ + if r1 == r0 goto +1; \ + exit; \ + r10 = 0; \ + exit; \ +" : + : __imm(bpf_get_prandom_u32) + : __clobber_all); +} + char _license[] SEC("license") = "GPL"; |