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refactoring eBPF: reduce stack-usage by writing directly into allocated buffer instead of onto stack #153

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merged 4 commits into from
Dec 10, 2024
Merged

refactoring eBPF: reduce stack-usage by writing directly into allocated buffer instead of onto stack #153

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e7f8199
corrected map-name in README
der-whity Dec 10, 2024
d8642be
refactoring: write data directly into reserved map-entry
der-whity Dec 10, 2024
711dd11
Merge branch 'dev' into 151-ebpf-refactoring
der-whity Dec 10, 2024
8bf479f
fix: undefined behavior ebpf
fhilgers Dec 10, 2024
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2 changes: 1 addition & 1 deletion rust/backend/ebpf/README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,7 @@ The maps `<hook-name>_PIDS` are HashMaps that store the pid as key and as value

| | type | functions to hook | map<entry-type> |
|---------------|------------|------------------------------------------------------------------------------|---------------------------------------------|
| vfs_write | KProbe | `vfs_write`, `vfs_write_ret` | `VFS_WRITE_CALLS<VfsWriteCall>` |
| vfs_write | KProbe | `vfs_write`, `vfs_write_ret` | `VFS_WRITE_EVENTS<VfsWriteCall>` |
| sendmsg | Tracepoint | `sys_enter_sendmsg`, `sys_exit_sendmsg` | `SYS_SENDMSG_CALLS<SysSendmsgCall>` |
| JNIReferences | UProbe | `trace_add_local`, `trace_del_local`, `trace_add_global`, `trace_del_global` | `JNI_REF_CALLS<JNIRefCall>`, `JNI_REF_PIDS` |
| ... | ... | ... | ... |
18 changes: 10 additions & 8 deletions rust/backend/ebpf/src/jni_references.rs
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Expand Up @@ -27,13 +27,6 @@ fn handle_trace(ctx: ProbeContext, method: JNIMethodName) -> u32 {
return 0;
}

let call = JNICall {
pid,
tid,
begin_time_stamp: time_stamp,
method_name: method,
};

let mut entry = match JNI_REF_CALLS.reserve::<JNICall>(0) {
Some(entry) => entry,
None => {
Expand All @@ -42,7 +35,16 @@ fn handle_trace(ctx: ProbeContext, method: JNIMethodName) -> u32 {
}
};

entry.write(call);
let entry_mut = entry.as_mut_ptr();

unsafe {
(&raw mut (*entry_mut).pid).write(pid);
(&raw mut (*entry_mut).pid).write(pid);
(&raw mut (*entry_mut).tid).write(tid);
(&raw mut (*entry_mut).begin_time_stamp).write(time_stamp);
(&raw mut (*entry_mut).method_name).write(method);
}

entry.submit(0);

0
Expand Down
22 changes: 14 additions & 8 deletions rust/backend/ebpf/src/sys_sendmsg.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
//
// SPDX-License-Identifier: MIT


use aya_ebpf::{macros::{tracepoint, map}, maps::{HashMap, RingBuf}, programs::{TracePointContext}, EbpfContext, helpers::gen::bpf_ktime_get_ns};
use aya_log_ebpf::error;
use backend_common::{generate_id, SysSendmsgCall};
Expand Down Expand Up @@ -59,9 +60,8 @@ pub fn sys_exit_sendmsg(ctx: TracePointContext) -> u32 {
Some(duration) => duration,
};


let tgid = ctx.tgid();
let call_id = generate_id(pid, tgid);
let tid = ctx.tgid();
let call_id = generate_id(pid, tid);
let data = match unsafe { SYS_SENDMSG_TIMESTAMPS.get(&call_id) } {
None => {return 1}
Some(entry) => {entry}
Expand All @@ -74,19 +74,25 @@ pub fn sys_exit_sendmsg(ctx: TracePointContext) -> u32 {
return 0;
}

let result_data = SysSendmsgCall::new(pid, tgid, data.begin_time_stamp, data.fd, duration_nano_sec);

let mut entry = match SYS_SENDMSG_EVENTS.reserve::<SysSendmsgCall>(0) {
Some(entry) => entry,
None => {
error!(&ctx, "could not reserve space in SYS_SENDMSG_MAP");
error!(&ctx, "could not reserve space in map: SYS_SENDMSG_CALLS");
return 1;
}
};

entry.write(result_data);
entry.submit(0);
let entry_mut = entry.as_mut_ptr();

unsafe {
(&raw mut (*entry_mut).pid).write(pid);
(&raw mut (*entry_mut).tid).write(tid);
(&raw mut (*entry_mut).begin_time_stamp).write(data.begin_time_stamp);
(&raw mut (*entry_mut).fd).write(data.fd);
(&raw mut (*entry_mut).duration_nano_sec).write(duration_nano_sec);
}

entry.submit(0);

0
}
20 changes: 14 additions & 6 deletions rust/backend/ebpf/src/vfs_write.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
//
// SPDX-License-Identifier: MIT


use aya_ebpf::{
macros::{kprobe, map, kretprobe},
maps::{HashMap, RingBuf},
Expand Down Expand Up @@ -75,8 +76,8 @@ pub fn vfs_write_ret(ctx: RetProbeContext) -> Result<(), u32> {
Some(duration) => duration,
};

let tgid = ctx.tgid();
let call_id = generate_id(pid, tgid);
let tid = ctx.tgid();
let call_id = generate_id(pid, tid);
let data = match unsafe { VFS_WRITE_TIMESTAMPS.get(&call_id) } {
None => {return Err(0)}
Some(entry) => {entry}
Expand All @@ -88,17 +89,24 @@ pub fn vfs_write_ret(ctx: RetProbeContext) -> Result<(), u32> {
return Ok(());
}

let data = VfsWriteCall::new(pid, tgid, data.begin_time_stamp, data.fp, data.bytes_written);

let mut entry = match VFS_WRITE_EVENTS.reserve::<VfsWriteCall>(0) {
Some(entry) => entry,
None => {
error!(&ctx, "could not reserve space in VFS_WRITE_MAP");
error!(&ctx, "could not reserve space in map: VFS_WRITE_EVENTS");
return Err(0)
},
};

entry.write(data);
let entry_mut = entry.as_mut_ptr();

unsafe {
(&raw mut (*entry_mut).pid).write(pid);
(&raw mut (*entry_mut).tid).write(tid);
(&raw mut (*entry_mut).begin_time_stamp).write(data.begin_time_stamp);
(&raw mut (*entry_mut).fp).write(data.fp);
(&raw mut (*entry_mut).bytes_written).write(data.bytes_written);
}

entry.submit(0);


Expand Down