From 59ed76fe2f981bccde37bdddb465f260a96a2404 Mon Sep 17 00:00:00 2001 From: Song Liu Date: Thu, 26 May 2022 12:16:08 -0700 Subject: [PATCH 1/2] selftests/bpf: fix stacktrace_build_id with missing kprobe/urandom_read Kernel function urandom_read is replaced with urandom_read_iter. Therefore, kprobe on urandom_read is not working any more: [root@eth50-1 bpf]# ./test_progs -n 161 test_stacktrace_build_id:PASS:skel_open_and_load 0 nsec libbpf: kprobe perf_event_open() failed: No such file or directory libbpf: prog 'oncpu': failed to create kprobe 'urandom_read+0x0' \ perf event: No such file or directory libbpf: prog 'oncpu': failed to auto-attach: -2 test_stacktrace_build_id:FAIL:attach_tp err -2 161 stacktrace_build_id:FAIL Fix this by replacing urandom_read with urandom_read_iter in the test. Fixes: 1b388e7765f2 ("random: convert to using fops->read_iter()") Reported-by: Mykola Lysenko Signed-off-by: Song Liu Acked-by: David Vernet Link: https://lore.kernel.org/r/20220526191608.2364049-1-song@kernel.org Signed-off-by: Alexei Starovoitov --- tools/testing/selftests/bpf/progs/test_stacktrace_build_id.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/progs/test_stacktrace_build_id.c b/tools/testing/selftests/bpf/progs/test_stacktrace_build_id.c index 6c62bfb8bb6f..0c4426592a26 100644 --- a/tools/testing/selftests/bpf/progs/test_stacktrace_build_id.c +++ b/tools/testing/selftests/bpf/progs/test_stacktrace_build_id.c @@ -39,7 +39,7 @@ struct { __type(value, stack_trace_t); } stack_amap SEC(".maps"); -SEC("kprobe/urandom_read") +SEC("kprobe/urandom_read_iter") int oncpu(struct pt_regs *args) { __u32 max_len = sizeof(struct bpf_stack_build_id) From caff1fa4118cec4dfd4336521ebd22a6408a1e3e Mon Sep 17 00:00:00 2001 From: Menglong Dong Date: Tue, 24 May 2022 10:12:27 +0800 Subject: [PATCH 2/2] bpf: Fix probe read error in ___bpf_prog_run() I think there is something wrong with BPF_PROBE_MEM in ___bpf_prog_run() in big-endian machine. Let's make a test and see what will happen if we want to load a 'u16' with BPF_PROBE_MEM. Let's make the src value '0x0001', the value of dest register will become 0x0001000000000000, as the value will be loaded to the first 2 byte of DST with following code: bpf_probe_read_kernel(&DST, SIZE, (const void *)(long) (SRC + insn->off)); Obviously, the value in DST is not correct. In fact, we can compare BPF_PROBE_MEM with LDX_MEM_H: DST = *(SIZE *)(unsigned long) (SRC + insn->off); If the memory load is done by LDX_MEM_H, the value in DST will be 0x1 now. And I think this error results in the test case 'test_bpf_sk_storage_map' failing: test_bpf_sk_storage_map:PASS:bpf_iter_bpf_sk_storage_map__open_and_load 0 nsec test_bpf_sk_storage_map:PASS:socket 0 nsec test_bpf_sk_storage_map:PASS:map_update 0 nsec test_bpf_sk_storage_map:PASS:socket 0 nsec test_bpf_sk_storage_map:PASS:map_update 0 nsec test_bpf_sk_storage_map:PASS:socket 0 nsec test_bpf_sk_storage_map:PASS:map_update 0 nsec test_bpf_sk_storage_map:PASS:attach_iter 0 nsec test_bpf_sk_storage_map:PASS:create_iter 0 nsec test_bpf_sk_storage_map:PASS:read 0 nsec test_bpf_sk_storage_map:FAIL:ipv6_sk_count got 0 expected 3 $10/26 bpf_iter/bpf_sk_storage_map:FAIL The code of the test case is simply, it will load sk->sk_family to the register with BPF_PROBE_MEM and check if it is AF_INET6. With this patch, now the test case 'bpf_iter' can pass: $10 bpf_iter:OK Fixes: 2a02759ef5f8 ("bpf: Add support for BTF pointers to interpreter") Signed-off-by: Menglong Dong Signed-off-by: Daniel Borkmann Reviewed-by: Jiang Biao Reviewed-by: Hao Peng Cc: Ilya Leoshkevich Link: https://lore.kernel.org/bpf/20220524021228.533216-1-imagedong@tencent.com --- kernel/bpf/core.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index cacd8684c3c4..5f6f3f829b36 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -1953,6 +1953,11 @@ out: CONT; \ LDX_MEM_##SIZEOP: \ DST = *(SIZE *)(unsigned long) (SRC + insn->off); \ + CONT; \ + LDX_PROBE_MEM_##SIZEOP: \ + bpf_probe_read_kernel(&DST, sizeof(SIZE), \ + (const void *)(long) (SRC + insn->off)); \ + DST = *((SIZE *)&DST); \ CONT; LDST(B, u8) @@ -1960,15 +1965,6 @@ out: LDST(W, u32) LDST(DW, u64) #undef LDST -#define LDX_PROBE(SIZEOP, SIZE) \ - LDX_PROBE_MEM_##SIZEOP: \ - bpf_probe_read_kernel(&DST, SIZE, (const void *)(long) (SRC + insn->off)); \ - CONT; - LDX_PROBE(B, 1) - LDX_PROBE(H, 2) - LDX_PROBE(W, 4) - LDX_PROBE(DW, 8) -#undef LDX_PROBE #define ATOMIC_ALU_OP(BOP, KOP) \ case BOP: \