Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx> writes: > On Thu, 7 Aug 2025 at 15:25, <puranjay@xxxxxxxxxx> wrote: >> >> Yonghong Song <yonghong.song@xxxxxxxxx> writes: >> >> > On 8/6/25 1:58 AM, Puranjay Mohan wrote: >> >> Add selftests for testing the reporting of arena page faults through BPF >> >> streams. Two new bpf programs are added that read and write to an >> >> unmapped arena address and the fault reporting is verified in the >> >> userspace through streams. >> >> >> >> Signed-off-by: Puranjay Mohan <puranjay@xxxxxxxxxx> >> >> --- >> >> .../testing/selftests/bpf/prog_tests/stream.c | 24 ++++++++++++ >> >> tools/testing/selftests/bpf/progs/stream.c | 37 +++++++++++++++++++ >> >> 2 files changed, 61 insertions(+) >> >> >> >> diff --git a/tools/testing/selftests/bpf/prog_tests/stream.c b/tools/testing/selftests/bpf/prog_tests/stream.c >> >> index d9f0185dca61b..4bdde56de35b1 100644 >> >> --- a/tools/testing/selftests/bpf/prog_tests/stream.c >> >> +++ b/tools/testing/selftests/bpf/prog_tests/stream.c >> >> @@ -41,6 +41,22 @@ struct { >> >> "([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n" >> >> "|[ \t]+[^\n]+\n)*", >> >> }, >> >> + { >> >> + offsetof(struct stream, progs.stream_arena_read_fault), >> >> + "ERROR: Arena READ access at unmapped address 0x.*\n" >> >> + "CPU: [0-9]+ UID: 0 PID: [0-9]+ Comm: .*\n" >> >> + "Call trace:\n" >> >> + "([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n" >> >> + "|[ \t]+[^\n]+\n)*", >> >> + }, >> >> + { >> >> + offsetof(struct stream, progs.stream_arena_write_fault), >> >> + "ERROR: Arena WRITE access at unmapped address 0x.*\n" >> >> + "CPU: [0-9]+ UID: 0 PID: [0-9]+ Comm: .*\n" >> >> + "Call trace:\n" >> >> + "([a-zA-Z_][a-zA-Z0-9_]*\\+0x[0-9a-fA-F]+/0x[0-9a-fA-F]+\n" >> >> + "|[ \t]+[^\n]+\n)*", >> >> + }, >> >> }; >> >> >> >> static int match_regex(const char *pattern, const char *string) >> >> @@ -85,6 +101,14 @@ void test_stream_errors(void) >> >> continue; >> >> } >> >> #endif >> >> +#if !defined(__x86_64__) && !defined(__aarch64__) >> >> + ASSERT_TRUE(1, "Arena fault reporting unsupported, skip."); >> >> + if (i == 2 || i == 3) { >> >> + ret = bpf_prog_stream_read(prog_fd, 2, buf, sizeof(buf), &ropts); >> >> + ASSERT_EQ(ret, 0, "stream read"); >> >> + continue; >> >> + } >> >> +#endif >> >> >> >> ret = bpf_prog_stream_read(prog_fd, BPF_STREAM_STDERR, buf, sizeof(buf), &ropts); >> >> ASSERT_GT(ret, 0, "stream read"); >> >> diff --git a/tools/testing/selftests/bpf/progs/stream.c b/tools/testing/selftests/bpf/progs/stream.c >> >> index 35790897dc879..58ebff60cd96a 100644 >> >> --- a/tools/testing/selftests/bpf/progs/stream.c >> >> +++ b/tools/testing/selftests/bpf/progs/stream.c >> >> @@ -1,10 +1,15 @@ >> >> // SPDX-License-Identifier: GPL-2.0 >> >> /* Copyright (c) 2025 Meta Platforms, Inc. and affiliates. */ >> >> +#define BPF_NO_KFUNC_PROTOTYPES >> > >> > Do we have to defineBPF_NO_KFUNC_PROTOTYPES in the above? Without the above, we do not need >> > below extern bpf_res_spin_lock and bpf_res_spin_unlock. >> > >> >> If we don't define BPF_NO_KFUNC_PROTOTYPES then there are build failures >> for bpf_arena_alloc/free_pages() because the prototypes in vmlinux.h >> lack __arena attribute. > > I would address this by dropping the alloc/free. > Instead to work around "addr_space_cast insn in program without arena error", > insert a dummy store "ptr = &arena" in the program, where ptr is a > global void *. > I want to use alloc/free and not use a dummy address because because arena pointers are special as they are returned by alloc() with arena->user_vm_start added to them, and the bpf_prog_report_arena_violation() also adds back arena->user_vm_start to the 32 bit address received by the fault handler. If I use a random address in the bpf program, bpf_prog_report_arena_violation() will print a bogus address. So, I think we should keep using alloc/free for this test because we want to test this arena->user_vm_start addition as well. Thanks, Puranjay