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Merged
lizrice merged 9 commits into from
Mar 23, 2026
Merged

Errata - more idiomatic addressing for arrays, tidy string output #55

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1a8e4a9
Fix: cosmetic to match find-map string output exactly in chapter 5
lizrice Mar 23, 2026
12c2187
More idiomatic C for array address
lizrice Mar 23, 2026
8b8feda
Ensure data.path is null-terminated
lizrice Mar 23, 2026
3261e73
Update chapter7/hello.bpf.c
lizrice Mar 23, 2026
9044541
Ensure data.path is null-terminated for use as a string
lizrice Mar 23, 2026
698cc54
Ensure data.message is null-terminated for use as a string
lizrice Mar 23, 2026
83dba89
Initial plan
Copilot Mar 23, 2026
8ba9f99
Use bpf_probe_read_kernel_str for remaining string reads in chapter6 …
Copilot Mar 23, 2026
2d83e94
Merge pull request #57 from lizrice/copilot/sub-pr-55-again
lizrice Mar 23, 2026
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4 changes: 2 additions & 2 deletions chapter2/hello-buffer.py
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Original file line number Diff line number Diff line change
Expand Up @@ -18,8 +18,8 @@
data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;

bpf_get_current_comm(&data.command, sizeof(data.command));
bpf_probe_read_kernel(&data.message, sizeof(data.message), message);
bpf_get_current_comm(data.command, sizeof(data.command));
bpf_probe_read_kernel(data.message, sizeof(data.message), message);

output.perf_submit(ctx, &data, sizeof(data));

Expand Down
4 changes: 2 additions & 2 deletions chapter2/hello-file-ring-buffer.py
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Expand Up @@ -15,8 +15,8 @@
struct event_t event = {};

event.dfd = args->dfd;
bpf_probe_read_user_str(&event.filename, sizeof(event.filename), args->filename);
bpf_get_current_comm(&event.command, sizeof(event.command));
bpf_probe_read_user_str(event.filename, sizeof(event.filename), args->filename);
bpf_get_current_comm(event.command, sizeof(event.command));

bpf_trace_printk("File %d - %s", event.dfd, event.filename);
bpf_trace_printk(" opened by:%s", event.command);
Expand Down
6 changes: 3 additions & 3 deletions chapter4/hello-buffer-config.py
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Expand Up @@ -27,13 +27,13 @@
data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;

bpf_get_current_comm(&data.command, sizeof(data.command));
bpf_get_current_comm(data.command, sizeof(data.command));

p = config.lookup(&data.uid);
if (p != 0) {
bpf_probe_read_kernel(&data.message, sizeof(data.message), p->message);
bpf_probe_read_kernel(data.message, sizeof(data.message), p->message);
} else {
bpf_probe_read_kernel(&data.message, sizeof(data.message), message);
bpf_probe_read_kernel(data.message, sizeof(data.message), message);
}

output.perf_submit(ctx, &data, sizeof(data));
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6 changes: 3 additions & 3 deletions chapter4/hello-ring-buffer-config.py
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Original file line number Diff line number Diff line change
Expand Up @@ -27,13 +27,13 @@
data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;

bpf_get_current_comm(&data.command, sizeof(data.command));
bpf_get_current_comm(data.command, sizeof(data.command));

p = config.lookup(&data.uid);
if (p != 0) {
bpf_probe_read_kernel(&data.message, sizeof(data.message), p->message);
bpf_probe_read_kernel(data.message, sizeof(data.message), p->message);
} else {
bpf_probe_read_kernel(&data.message, sizeof(data.message), message);
bpf_probe_read_kernel(data.message, sizeof(data.message), message);
}

output.ringbuf_output(&data, sizeof(data), 0);
Expand Down
2 changes: 1 addition & 1 deletion chapter5/find-map.c
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Expand Up @@ -14,6 +14,6 @@ int main()
printf("No FD\n");
} else {
bpf_obj_get_info_by_fd(findme, &info, &len);
printf("name %s\n", info.name);
printf("Name: %s\n", info.name);
}
}
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8 changes: 4 additions & 4 deletions chapter5/hello-buffer-config.bpf.c
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Expand Up @@ -32,14 +32,14 @@ int BPF_KPROBE_SYSCALL(hello, const char *pathname)
data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;

bpf_get_current_comm(&data.command, sizeof(data.command));
bpf_probe_read_user_str(&data.path, sizeof(data.path), pathname);
bpf_get_current_comm(data.command, sizeof(data.command));
bpf_probe_read_user_str(data.path, sizeof(data.path), pathname);

p = bpf_map_lookup_elem(&my_config, &data.uid);
if (p != 0) {
bpf_probe_read_kernel_str(&data.message, sizeof(data.message), p->message);
bpf_probe_read_kernel_str(data.message, sizeof(data.message), p->message);
} else {
bpf_probe_read_kernel_str(&data.message, sizeof(data.message), message);
bpf_probe_read_kernel_str(data.message, sizeof(data.message), message);
}

bpf_perf_event_output(ctx, &output, BPF_F_CURRENT_CPU, &data, sizeof(data));
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6 changes: 3 additions & 3 deletions chapter6/hello-verifier.bpf.c
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Expand Up @@ -45,9 +45,9 @@ int kprobe_exec(void *ctx)
}

if (p != 0) {
bpf_probe_read_kernel(&data.message, sizeof(data.message), p->message);
bpf_probe_read_kernel_str(data.message, sizeof(data.message), p->message);
} else {
bpf_probe_read_kernel(&data.message, sizeof(data.message), message);
bpf_probe_read_kernel_str(data.message, sizeof(data.message), message);
}
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lizrice marked this conversation as resolved.

// Changing this to <= means and c could have value beyond the bounds of the
Expand All @@ -66,7 +66,7 @@ int kprobe_exec(void *ctx)
bpf_printk("%c", a);
}

bpf_get_current_comm(&data.command, sizeof(data.command));
bpf_get_current_comm(data.command, sizeof(data.command));
bpf_perf_event_output(ctx, &output, BPF_F_CURRENT_CPU, &data, sizeof(data));

return 0;
Expand Down
30 changes: 15 additions & 15 deletions chapter7/hello.bpf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -28,13 +28,13 @@ int BPF_KPROBE_SYSCALL(kprobe_sys_execve, const char *pathname)
{
struct data_t data = {};

bpf_probe_read_kernel(&data.message, sizeof(data.message), kprobe_sys_msg);
bpf_probe_read_kernel(data.message, sizeof(data.message), kprobe_sys_msg);
bpf_printk("%s: pathname: %s", kprobe_sys_msg, pathname);

data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;
bpf_get_current_comm(&data.command, sizeof(data.command));
bpf_probe_read_user(&data.path, sizeof(data.path), pathname);
bpf_get_current_comm(data.command, sizeof(data.command));
bpf_probe_read_user_str(data.path, sizeof(data.path), pathname);

bpf_perf_event_output(ctx, &output, BPF_F_CURRENT_CPU, &data, sizeof(data));
return 0;
Expand All @@ -46,14 +46,14 @@ SEC("kprobe/do_execve")
int BPF_KPROBE(kprobe_do_execve, struct filename *filename) {
struct data_t data = {};

bpf_probe_read_kernel(&data.message, sizeof(data.message), kprobe_msg);
bpf_probe_read_kernel(data.message, sizeof(data.message), kprobe_msg);

data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;

bpf_get_current_comm(&data.command, sizeof(data.command));
bpf_get_current_comm(data.command, sizeof(data.command));
const char *name = BPF_CORE_READ(filename, name);
bpf_probe_read_kernel(&data.path, sizeof(data.path), name);
bpf_probe_read_kernel_str(data.path, sizeof(data.path), name);

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lizrice marked this conversation as resolved.
bpf_printk("%s: filename->name: %s", kprobe_msg, name);

Expand All @@ -69,14 +69,14 @@ SEC("fentry/do_execve")
int BPF_PROG(fentry_execve, struct filename *filename) {
struct data_t data = {};

bpf_probe_read_kernel(&data.message, sizeof(data.message), fentry_msg);
bpf_probe_read_kernel(data.message, sizeof(data.message), fentry_msg);

data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;

bpf_get_current_comm(&data.command, sizeof(data.command));
bpf_get_current_comm(data.command, sizeof(data.command));
const char *name = BPF_CORE_READ(filename, name);
bpf_probe_read_kernel(&data.path, sizeof(data.path), name);
bpf_probe_read_kernel_str(data.path, sizeof(data.path), name);

bpf_printk("%s: filename->name: %s", fentry_msg, name);

Expand Down Expand Up @@ -113,14 +113,14 @@ SEC("tp/syscalls/sys_enter_execve")
int tp_sys_enter_execve(struct my_syscalls_enter_execve *ctx) {
struct data_t data = {};

bpf_probe_read_kernel(&data.message, sizeof(data.message), tp_msg);
bpf_probe_read_kernel(data.message, sizeof(data.message), tp_msg);
bpf_printk("%s: ctx->filename_ptr: %s", tp_msg, ctx->filename_ptr);

data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;

bpf_get_current_comm(&data.command, sizeof(data.command));
bpf_probe_read_user(&data.path, sizeof(data.path), ctx->filename_ptr);
bpf_get_current_comm(data.command, sizeof(data.command));
bpf_probe_read_user_str(data.path, sizeof(data.path), ctx->filename_ptr);

bpf_perf_event_output(ctx, &output, BPF_F_CURRENT_CPU, &data, sizeof(data));
return 0;
Expand All @@ -134,14 +134,14 @@ int tp_btf_exec(struct trace_event_raw_sched_process_exec *ctx)
struct data_t data = {};
// pid_t pid = ctx->pid;

bpf_probe_read_kernel(&data.message, sizeof(data.message), tp_btf_exec_msg);
bpf_probe_read_kernel(data.message, sizeof(data.message), tp_btf_exec_msg);

data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;

// TODO!! Resolve issues accessing data that isn't aligned to an 8-byte boundary
// bpf_printk("%s %d\n", tp_btf_exec_msg, pid);
// bpf_probe_read_kernel_str(&data.command, sizeof(data.command), ctx->pid);
// bpf_probe_read_kernel_str(data.command, sizeof(data.command), ctx->pid);

bpf_perf_event_output(ctx, &output, BPF_F_CURRENT_CPU, &data, sizeof(data));
return 0;
Expand All @@ -152,7 +152,7 @@ int raw_tp_exec(struct bpf_raw_tracepoint_args *ctx)
{
struct data_t data = {};

bpf_probe_read_kernel(&data.message, sizeof(data.message), raw_tp_exec_msg);
bpf_probe_read_kernel(data.message, sizeof(data.message), raw_tp_exec_msg);

data.pid = bpf_get_current_pid_tgid() >> 32;
data.uid = bpf_get_current_uid_gid() & 0xFFFFFFFF;
Expand Down