It indicates to a debugger that the thread is stopped at the
kernel->user exit path.
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D37590
This will always sleep at least once, so it's a slow path by definition.
Reviewed By: kib
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D33387
In 6e66030c4c, additional ptracestop was added in order
to implement PTRACE_EVENT_EXEC. Make it only apply to cases
where the debugger is a Linux processes; native FreeBSD
debuggers can trace Linux processes too, but they don't
expect that additonal ptracestop.
Fixes: 6e66030c4c
Reported By: kib
Reviewed By: kib
Sponsored By: EPSRC
Differential Revision: https://reviews.freebsd.org/D32726
The syscall number is stored in the same register as the syscall return
on amd64 (and possibly other architectures) and so it is impossible to
recover in the signal handler after the call has returned. This small
tweak delivers it in the `si_value` field of the signal, which is
sufficient to catch capability violations and emulate them with a call
to a more-privileged process in the signal handler.
This reapplies 3a522ba1bc with a fix for
the static assertion failure on i386.
Approved by: markj (mentor)
Reviewed by: kib, bcr (manpages)
Differential Revision: https://reviews.freebsd.org/D29185
The syscall number is stored in the same register as the syscall return
on amd64 (and possibly other architectures) and so it is impossible to
recover in the signal handler after the call has returned. This small
tweak delivers it in the `si_value` field of the signal, which is
sufficient to catch capability violations and emulate them with a call
to a more-privileged process in the signal handler.
Approved by: markj (mentor)
Reviewed by: kib, bcr (manpages)
Differential Revision: https://reviews.freebsd.org/D29185
Restart syscalls and some sync operations when filesystem indicated
ERELOOKUP condition, mostly for VOPs operating on metdata. In
particular, lookup results cached in the inode/v_data is no longer
valid and needs recalculating. Right now this should be nop.
Assert that ERELOOKUP is catched everywhere and not returned to
userspace, by asserting that td_errno != ERELOOKUP on syscall return
path.
In collaboration with: pho
Reviewed by: mckusick (previous version), markj
Tested by: markj (syzkaller), pho
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D26136
If we hadn't been traced in the first place when syscallenter()
started executing, we can ignore TDB_USERWR. TDB_USERWR can get set,
sure, but if it does, it's because the debugger raced with the syscall,
and it cannot depend on winning that race.
Reviewed by: kib
MFC after: 2 weeks
Sponsored by: EPSRC
Differential Revision: https://reviews.freebsd.org/D26585
r326145 corrected do_execve() to return EJUSTRETURN upon success so that
important registers are not clobbered. This had the side effect of tapping
out 'failures' for all *execve(2) audit records, which is less than useful
for auditing purposes.
Audit exec returns earlier, where we can know for sure that EJUSTRETURN
translates to success. Note that this unsets TDP_AUDITREC as we commit the
audit record, so the usual audit in the syscall return path will do nothing.
PR: 249179
Reported by: Eirik Oeverby <ltning-freebsd anduin net>
Reviewed by: csjp, kib
MFC after: 1 week
Sponsored by: Klara, Inc.
Differential Revision: https://reviews.freebsd.org/D26922
Modern debuggers and process tracers use ptrace() rather than procfs
for debugging. ptrace() has a supserset of functionality available
via procfs and new debugging features are only added to ptrace().
While the two debugging services share some fields in struct proc,
they each use dedicated fields and separate code. This results in
extra complexity to support a feature that hasn't been enabled in the
default install for several years.
PR: 244939 (exp-run)
Reviewed by: kib, mjg (earlier version)
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D23837
On machines with SMAP, fueword executes two serializing instructions
which can be seen in microbenchmarks.
As a measure to restore microbenchmark numbers, only read the word on
the attempt to deliver signal in ast(). If the word is set, signal is
not delivered and word is kept, preventing interruption of
interruptible sleeps by signals until userspace calls
sigfastblock(UNBLOCK) which clears the word.
This way, the spurious EINTR that userspace can see while in critical
section is on first interruptible sleep, if a signal is pending, and
on signal posting. It is believed that it is not important for rtld
and lbithr critical sections. It might be visible for the application
code e.g. for the callback of dl_iterate_phdr(3), but again the belief
is that the non-compliance is acceptable. Most important is that the
retry of the sleeping syscall does not interrupt unless additional
signal is posted.
For now I added the knob kern.sigfastblock_fetch_always to enable the
word read on syscall entry to be able to diagnose possible issues due
to spurious EINTR.
While there, do some code restructuting to have all sigfastblock()
handling located in kern_sig.c.
Reviewed by: jeff
Discussed with: mjg
Tested by: pho
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D23622
This in particular significantly shortens amd64_syscall, which otherwise
keeps jumping forward over 2KB of code in total.
Note some of these branches should be either eliminated altogether or
coalesced.
A new syscall sigfastblock(2) is added which registers a uint32_t
variable as containing the count of blocks for signal delivery. Its
content is read by kernel on each syscall entry and on AST processing,
non-zero count of blocks is interpreted same as the signal mask
blocking all signals.
The biggest downside of the feature that I see is that memory
corruption that affects the registered fast sigblock location, would
cause quite strange application misbehavior. For instance, the process
would be immune to ^C (but killable by SIGKILL).
With consumers (rtld and libthr added), benchmarks do not show a
slow-down of the syscalls in micro-measurements, and macro benchmarks
like buildworld do not demonstrate a difference. Part of the reason is
that buildworld time is dominated by compiler, and clang already links
to libthr. On the other hand, small utilities typically used by shell
scripts have the total number of syscalls cut by half.
The syscall is not exported from the stable libc version namespace on
purpose. It is intended to be used only by our C runtime
implementation internals.
Tested by: pho
Disscussed with: cem, emaste, jilles
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D12773
syscallret() doesn't use error anymore. Fix a few other places to permit
removing the return value from syscallenter() entirely.
- Remove a duplicated assertion from arm's syscall().
- Use td_errno for amd64_syscall_ret_flush_l1d.
Reviewed by: kib
MFC after: 1 month
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D2090
Early errors prior to a system call did not set td_errno. This commit
sets td_errno for all errors during syscallenter(). As a result,
syscallret() can now always use td_errno without checking TDP_NERRNO.
Reviewed by: kib
MFC after: 1 month
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D20898
This is more consistent with the rest of the function and lets us
unindent most of the function.
Reviewed by: kib
MFC after: 1 month
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D20897
This unreliably breaks libc handling of vfork where forking succeded,
but execve did not.
vfork code in libc performs waitpid with WNOHANG in case of failed exec.
With the fix exit codepath was waking up the parent before the child
fully transitioned to a zombie. Woken up parent would waitpid, which
could find a not-yet-zombie child and fail to reap it due to the WNOHANG
flag.
While removing the flag fixes the problem, it is not an option due to older
releases which would still suffer from the kernel change.
Revert the fix until a solution can be worked out.
Note that while use-after-free which gets back due to the revert is a real
bug, it's side-effects are limited due to the fact that struct proc memory
is never released by UMA.
The pointer to the child is stored without any reference held. Then it is
blindly used to wait until P_PPWAIT is cleared. However, if the child is
autoreaped it could have exited and get freed before the parent started
waiting.
Use the existing hold mechanism to mitigate the problem. Most common case
of doing exec remains unchanged. The corner case of doing exit performs
wake up before waiting for holds to clear.
Reviewed by: kib
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D18295
While here predict false.
Note the code is wrong (regardless of this change). Dereference of the
pointer can race with module unload. A fix would set the probe to a
nop stub instead of NULL.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.
Initially, only tag files that use BSD 4-Clause "Original" license.
RelNotes: yes
Differential Revision: https://reviews.freebsd.org/D13133
struct thread.
For all architectures, the syscall trap handlers have to allocate the
structure on the stack. The structure takes 88 bytes on 64bit arches
which is not negligible. Also, it cannot be easily found by other
code, which e.g. caused duplication of some members of the structure
to struct thread already. The change removes td_dbg_sc_code and
td_dbg_sc_nargs which were directly copied from syscall_args.
The structure is put into the copied on fork part of the struct thread
to make the syscall arguments information correct in the child after
fork.
This move will also allow several more uses shortly.
Reviewed by: jhb (previous version)
Sponsored by: The FreeBSD Foundation
MFC after: 3 weeks
X-Differential revision: https://reviews.freebsd.org/D11080
in place. To do per-cpu stats, convert all fields that previously were
maintained in the vmmeters that sit in pcpus to counter(9).
- Since some vmmeter stats may be touched at very early stages of boot,
before we have set up UMA and we can do counter_u64_alloc(), provide an
early counter mechanism:
o Leave one spare uint64_t in struct pcpu, named pc_early_dummy_counter.
o Point counter(9) fields of vmmeter to pcpu[0].pc_early_dummy_counter,
so that at early stages of boot, before counters are allocated we already
point to a counter that can be safely written to.
o For sparc64 that required a whole dummy pcpu[MAXCPU] array.
Further related changes:
- Don't include vmmeter.h into pcpu.h.
- vm.stats.vm.v_swappgsout and vm.stats.vm.v_swappgsin changed to 64-bit,
to match kernel representation.
- struct vmmeter hidden under _KERNEL, and only vmstat(1) is an exclusion.
This is based on benno@'s 4-year old patch:
https://lists.freebsd.org/pipermail/freebsd-arch/2013-July/014471.html
Reviewed by: kib, gallatin, marius, lidl
Differential Revision: https://reviews.freebsd.org/D10156
When a thread is stopped in ptracestop(), the ptrace(2) user may request
a signal be delivered upon resumption of the thread. Heretofore, those signals
were discarded unless ptracestop()'s caller was issignal(). Fix this by
modifying ptracestop() to queue up signals requested by the ptrace user that
will be delivered when possible. Take special care when the signal is SIGKILL
(usually generated from a PT_KILL request); no new stop events should be
triggered after a PT_KILL.
Add a number of tests for the new functionality. Several tests were authored
by jhb.
PR: 212607
Reviewed by: kib
Approved by: kib (mentor)
MFC after: 2 weeks
Sponsored by: Dell EMC
In collaboration with: jhb
Differential Revision: https://reviews.freebsd.org/D9260
Both can be used to cause processes in capability mode to receive
SIGTRAP when ENOTCAPABLE or ECAPMODE errors are returned from
syscalls.
Idea by: emaste
Reviewed by: oshogbo (previous version), emaste
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D7965
First, PL_FLAG_FORKED events now also set a PL_FLAG_VFORKED flag when
the new child was created via vfork() rather than fork(). Second, a
new PL_FLAG_VFORK_DONE event can now be enabled via the PTRACE_VFORK
event mask. This new stop is reported after the vfork parent resumes
due to the child calling exit or exec. Debuggers can use this stop to
reinsert breakpoints in the vfork parent process before it resumes.
Reviewed by: kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D7045
ptrace() now stores a mask of optional events in p_ptevents. Currently
this mask is a single integer, but it can be expanded into an array of
integers in the future.
Two new ptrace requests can be used to manipulate the event mask:
PT_GET_EVENT_MASK fetches the current event mask and PT_SET_EVENT_MASK
sets the current event mask.
The current set of events include:
- PTRACE_EXEC: trace calls to execve().
- PTRACE_SCE: trace system call entries.
- PTRACE_SCX: trace syscam call exits.
- PTRACE_FORK: trace forks and auto-attach to new child processes.
- PTRACE_LWP: trace LWP events.
The S_PT_SCX and S_PT_SCE events in the procfs p_stops flags have
been replaced by PTRACE_SCE and PTRACE_SCX. PTRACE_FORK replaces
P_FOLLOW_FORK and PTRACE_LWP replaces P2_LWP_EVENTS.
The PT_FOLLOW_FORK and PT_LWP_EVENTS ptrace requests remain for
compatibility but now simply toggle corresponding flags in the
event mask.
While here, document that PT_SYSCALL, PT_TO_SCE, and PT_TO_SCX both
modify the event mask and continue the traced process.
Reviewed by: kib
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D7044
Rather than pushing all eight possible arguments into dtrace_probe()'s
stack frame, make the syscall_args struct for the current syscall available
via the current thread. Using a custom getargval method for the systrace
provider, this allows any syscall argument to be fetched, even in kernels
that have modified the maximum number of system call arguments.
Sponsored by: EMC / Isilon Storage Division
For CloudABI we need to initialize the registers of new threads
differently based on whether the thread got created through a fork or
through simple thread creation.
Add a flag, TDP_FORKING, that is set by do_fork() and cleared by
fork_exit(). This can be tested against in schedtail.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D3973
- Always set td_dbg_sc_* when P_TRACED is set on system call entry
even if the debugger is not tracing system call entries. This
ensures the fields are valid when reporting other stops that
occur at system call boundaries such as for PT_FOLLOW_FORKS or
when only tracing system call exits.
- Set TDB_SCX when reporting the stop for a new child process in
fork_return(). This causes the event to be reported as a system
call exit.
- Report a system call exit event in fork_return() for new threads in
a traced process.
- Copy td_dbg_sc_* to new threads instead of zeroing. This ensures
that td_dbg_sc_code in particular will report the system call that
created the new thread or process when it reports a system call
exit event in fork_return().
- Add new ptrace tests to verify that new child processes and threads
report system call exit events with a valid pl_syscall_code via
PT_LWPINFO.
Reviewed by: kib
Differential Revision: https://reviews.freebsd.org/D3822
TDB_USERWR flag may still be set after a debugger detaches from a
process via PT_DETACH. Previously the flag would never be cleared
forcing a double fetch of the system call arguments for each system
call. Note that the flag cannot be cleared at PT_DETACH time in case
one of the threads in the process is currently stopped in
syscallenter() and the debugger has modified the arguments for that
pending system call before detaching.
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D3678
and exit events. procfs stop events for system call tracing report these
values (argument count for system call entry and code for system call exit),
but ptrace() does not provide this information. (Note that while the system
call code can be determined in an ABI-specific manner during system call
entry, it is not generally available during system call exit.)
The values are exported via new fields at the end of struct ptrace_lwpinfo
available via PT_LWPINFO.
Reviewed by: kib
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D3536
Thread credentials are maintained as follows: each thread has a pointer to
creds and a reference on them. The pointer is compared with proc's creds on
userspace<->kernel boundary and updated if needed.
This patch introduces a counter which can be compared instead, so that more
structures can use this scheme without adding more comparisons on the boundary.
for the suspension.
Currently, the loop performs uninterruptible cv_wait(9) call, which
prevents suspension until child allows further execution of parent.
If child is stopped, suspension or single-threading is delayed
indefinitely.
Create a helper thread_suspend_check_needed() to identify the need for
a call to thread_suspend_check(). It is required since call to the
thread_suspend_check() cannot be safely done while owning the child
(p2) process lock. Only when suspension is needed, drop p2 lock and
call thread_suspend_check(). Perform wait for cv with timeout, in
case suspend is requested after wait started; I do not see a better
way to interrupt the wait.
Reported and tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
further refinement is required as some device drivers intended to be
portable over FreeBSD versions rely on __FreeBSD_version to decide whether
to include capability.h.
MFC after: 3 weeks
