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nia-enia-e
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remove some unnecessary state, small refactor
1 parent 09556c1 commit 6df5ade

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+63
-66
lines changed

1 file changed

+63
-66
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‎src/shims/trace.rs

Lines changed: 63 additions & 66 deletions
Original file line numberDiff line numberDiff line change
@@ -258,11 +258,6 @@ fn sv_loop(listener: ChildListener, t_event: ipc::IpcSender<MemEvents>) -> ! {
258258
// Memory allocated on the MiriMachine
259259
let mut ch_pages = vec![];
260260

261-
// Random bits of syscall-related state
262-
let mut enter = true;
263-
let mut flush_mapped = None;
264-
let mut munmap_args = None;
265-
266261
// Straight up magic numbers we need
267262
let malloc_addr = libc::malloc as usize;
268263
let malloc_bytes = unsafe { (malloc_addr as *mut i64).read_volatile() }; // i'm sorry
@@ -275,7 +270,6 @@ fn sv_loop(listener: ChildListener, t_event: ipc::IpcSender<MemEvents>) -> ! {
275270
let mut retcode = 0;
276271

277272
#[allow(clippy::cast_possible_wrap)]
278-
#[allow(clippy::arithmetic_side_effects)]
279273
'listen: for evt in listener {
280274
match evt {
281275
ExecEvent::Status(wait_status) =>
@@ -316,71 +310,25 @@ fn sv_loop(listener: ChildListener, t_event: ipc::IpcSender<MemEvents>) -> ! {
316310
wait::WaitStatus::PtraceSyscall(pid) => {
317311
let regs = ptrace::getregs(pid).unwrap();
318312
let syscall_nr = regs.syscall_nr();
319-
if enter {
320-
if syscall_nr as i64 == libc::SYS_mmap {
313+
match syscall_nr as i64 {
314+
n if n == libc::SYS_mmap => {
315+
// No need for a discrete fn here, it's very tiny
321316
let len = regs.arg2();
322-
flush_mapped = Some(len);
323-
} else if syscall_nr as i64 == libc::SYS_munmap {
324-
// The unmap call might hit multiple mappings we've saved,
325-
// or overlap with them partially (or both)
326-
let um_start = regs.arg1();
327-
let um_len = regs.arg2();
328-
let um_end = um_start + um_len;
329-
let mut idxes = vec![];
330-
for (idx, &(mp_start, len)) in mappings.iter().enumerate() {
331-
let mp_end = mp_start + len;
332-
let cond = (mp_start..mp_end).contains(&um_start)
333-
|| (mp_start..mp_end).contains(&um_end)
334-
|| (um_start..um_end).contains(&mp_start);
335-
336-
if cond {
337-
idxes.push(idx);
338-
}
339-
}
340-
if !idxes.is_empty() {
341-
// We iterate thru this later while removing elements so if
342-
// it's not reversed we will mess up the mappings badly!
343-
idxes.reverse();
344-
munmap_args = Some((idxes, um_start, um_len));
345-
}
346-
} // TODO: handle brk/sbrk
347-
} else {
348-
if syscall_nr as i64 == libc::SYS_mmap {
317+
ptrace::syscall(pid, None).unwrap();
318+
let _ = wait::waitpid(pid, None).unwrap();
319+
let regs = ptrace::getregs(pid).unwrap();
349320
if regs.retval() as isize > 0 {
350-
if let Some(len) = flush_mapped.take() {
351-
let addr = regs.retval();
352-
mappings.push((addr, len as _));
353-
} else {
354-
eprintln!(
355-
"Process returned from mmap syscall without entering it? Attempting to continue..."
356-
);
357-
}
321+
let addr = regs.retval();
322+
mappings.push((addr, len as _));
358323
}
359-
} else if syscall_nr as i64 == libc::SYS_munmap {
360-
if let Some((idxes, um_start, um_len)) = munmap_args.take() {
361-
if regs.retval() as isize > 0 {
362-
// Unmap succeeded, so take out the mapping(s) from our list
363-
// but it may be only partial so we may readd some sections
364-
for idx in idxes {
365-
let um_end = um_start + um_len;
366-
let (mp_start, mp_len) = mappings.remove(idx);
367-
let mp_end = mp_len + mp_len;
368-
369-
if mp_start < um_start {
370-
let preserved_len_head = um_start - mp_start;
371-
mappings.push((mp_start, preserved_len_head));
372-
}
373-
if mp_end > um_end {
374-
let preserved_len_tail = mp_end - um_end;
375-
mappings.push((um_end, preserved_len_tail));
376-
}
377-
}
378-
}
379-
}
380-
}
324+
},
325+
n if n == libc::SYS_munmap => {
326+
handle_munmap(pid, regs, &mut mappings);
327+
},
328+
// TODO: handle brk/sbrk
329+
_ => (),
381330
}
382331

383-
enter = !enter;
384332
ptrace::syscall(pid, None).unwrap();
385333
}
386334
_ => (),
@@ -428,6 +376,53 @@ fn sv_loop(listener: ChildListener, t_event: ipc::IpcSender<MemEvents>) -> ! {
428376
std::process::exit(retcode);
429377
}
430378

379+
#[allow(clippy::arithmetic_side_effects)]
380+
#[allow(clippy::cast_possible_wrap)]
381+
fn handle_munmap(pid: unistd::Pid, regs: libc::user_regs_struct, mappings: &mut Vec<(usize, usize)>) {
382+
// The unmap call might hit multiple mappings we've saved,
383+
// or overlap with them partially (or both)
384+
let um_start = regs.arg1();
385+
let um_len = regs.arg2();
386+
let um_end = um_start + um_len;
387+
let mut idxes = vec![];
388+
for (idx, &(mp_start, len)) in mappings.iter().enumerate() {
389+
let mp_end = mp_start + len;
390+
let cond = (mp_start..mp_end).contains(&um_start)
391+
|| (mp_start..mp_end).contains(&um_end)
392+
|| (um_start..um_end).contains(&mp_start);
393+
394+
if cond {
395+
idxes.push(idx);
396+
}
397+
}
398+
// We iterate thru this while removing elements so if
399+
// it's not reversed we will mess up the mappings badly!
400+
idxes.reverse();
401+
402+
ptrace::syscall(pid, None).unwrap();
403+
let _ = wait::waitpid(pid, None).unwrap();
404+
let regs = ptrace::getregs(pid).unwrap();
405+
406+
if regs.retval() as isize > 0 {
407+
// Unmap succeeded, so take out the mapping(s) from our list
408+
// but it may be only partial so we may readd some sections
409+
for idx in idxes {
410+
let um_end = um_start + um_len;
411+
let (mp_start, mp_len) = mappings.remove(idx);
412+
let mp_end = mp_len + mp_len;
413+
414+
if mp_start < um_start {
415+
let preserved_len_head = um_start - mp_start;
416+
mappings.push((mp_start, preserved_len_head));
417+
}
418+
if mp_end > um_end {
419+
let preserved_len_tail = mp_end - um_end;
420+
mappings.push((um_end, preserved_len_tail));
421+
}
422+
}
423+
}
424+
}
425+
431426
#[allow(clippy::cast_possible_wrap)]
432427
#[allow(clippy::arithmetic_side_effects)]
433428
fn handle_segfault(
@@ -604,6 +599,8 @@ fn intercept_retptr(
604599
ptr
605600
}
606601

602+
603+
607604
// We only get dropped into these functions via offsetting the instr pointer
608605
// manually, so we *must not ever* unwind from it
609606
pub unsafe extern "C" fn mempr_off() {

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