On 8/27/25 8:37 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 | 33 +++++++++++++++- tools/testing/selftests/bpf/progs/stream.c | 39 +++++++++++++++++++ 2 files changed, 71 insertions(+), 1 deletion(-) diff --git a/tools/testing/selftests/bpf/prog_tests/stream.c b/tools/testing/selftests/bpf/prog_tests/stream.c index 36a1a1ebde692..8fdc83260ea14 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)@@ -63,6 +79,7 @@ void test_stream_errors(void) struct stream *skel; int ret, prog_fd; char buf[1024]; + char fault_addr[64] = {0};
You can replace '{0}' to '{}' so the whole array will be initialized.
skel = stream__open_and_load();if (!ASSERT_OK_PTR(skel, "stream__open_and_load")) @@ -85,6 +102,14 @@ 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; + } +#endifret = bpf_prog_stream_read(prog_fd, BPF_STREAM_STDERR, buf, sizeof(buf), &ropts);ASSERT_GT(ret, 0, "stream read"); @@ -92,8 +117,14 @@ void test_stream_errors(void) buf[ret] = '\0';ret = match_regex(stream_error_arr[i].errstr, buf);- if (!ASSERT_TRUE(ret == 1, "regex match")) + if (ret && (i == 2 || i == 3)) { + sprintf(fault_addr, "0x%lx", skel->bss->fault_addr); + ret = match_regex(fault_addr, buf); + } + if (!ASSERT_TRUE(ret == 1, "regex match")) { fprintf(stderr, "Output from stream:\n%s\n", buf); + fprintf(stderr, "Fault Addr: 0x%lx\n", skel->bss->fault_addr);
This will fault addr even for i == 0 or i == 1 and those address may be confusing for test 0/1.
+ } }stream__destroy(skel);diff --git a/tools/testing/selftests/bpf/progs/stream.c b/tools/testing/selftests/bpf/progs/stream.c index 35790897dc879..9de015ac3ced5 100644 --- a/tools/testing/selftests/bpf/progs/stream.c +++ b/tools/testing/selftests/bpf/progs/stream.c @@ -5,6 +5,7 @@ #include <bpf/bpf_helpers.h> #include "bpf_misc.h" #include "bpf_experimental.h" +#include "bpf_arena_common.h"struct arr_elem {struct bpf_res_spin_lock lock; @@ -17,10 +18,17 @@ struct { __type(value, struct arr_elem); } arrmap SEC(".maps");+struct {+ __uint(type, BPF_MAP_TYPE_ARENA); + __uint(map_flags, BPF_F_MMAPABLE); + __uint(max_entries, 1); /* number of pages */ +} arena SEC(".maps"); + #define ENOSPC 28 #define _STR "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"int size;+u64 fault_addr;SEC("syscall")__success __retval(0) @@ -76,4 +84,35 @@ int stream_syscall(void *ctx) return 0; }+SEC("syscall")+__success __retval(0) +int stream_arena_write_fault(void *ctx) +{ + struct bpf_arena *ptr = (void *)&arena; + u64 user_vm_start; + + barrier_var(ptr);
Do we need this barrier_var()? I tried llvm20 and it works fine without the above barrier_var().
+ user_vm_start = ptr->user_vm_start; +
Remove this line.
+ fault_addr = user_vm_start + 0xbeef; + *(u32 __arena *)(user_vm_start + 0xbeef) = 1;
Simplify to *(u32 __arena *)fault = 1;
+
Remove this line.
+ return 0;
+}
+
+SEC("syscall")
+__success __retval(0)
+int stream_arena_read_fault(void *ctx)
+{
+ struct bpf_arena *ptr = (void *)&arena;
+ u64 user_vm_start;
+
+ barrier_var(ptr);
Is this necessary?
+ user_vm_start = ptr->user_vm_start; +
Remove this line.
+ fault_addr = user_vm_start + 0xbeef; +
Remove this line.
+ return *(u32 __arena *)(user_vm_start + 0xbeef);
return*(u32 __arena *)fault_addr.
+}
+
char _license[] SEC("license") = "GPL";
