MFC r365284:

Always report ENOSYS in init

While rare, encountering an unimplemented system call early in init is
catastrophic and difficult to debug. Even after a SIGSYS handler is
registered, such configurations are problematic. As such, always report
such events for pid 1 (following kern.lognosys if non-zero).

Reviewed by: kevans, imp
Obtained from: CheriBSD (plus suggestions from kevans)
Sponsored by: DARPA
Differential Revision: https://reviews.freebsd.org/D26288

MFC r355146:
Ease the life of PT_TO_SCE/PT_TO_SCX users when debuggee sleeps in
sigsuspend(2)/sig{timed,}wait(2).

MFC r352711-r352712: Address posix_spawn(3) signal issues

r352711:
rfork(2): add RFSPAWN flag

When RFSPAWN is passed, rfork exhibits vfork(2) semantics but also resets
signal handlers in the child during creation to avoid a point of corruption
of parent state from the child.

This flag will be used by posix_spawn(3) to handle potential signal issues.

Reviewed by: jilles, kib
Differential Revision: https://reviews.freebsd.org/D19058

r352712:
posix_spawn(3): handle potential signal issues with vfork

Described in [1], signal handlers running in a vfork child have
opportunities to corrupt the parent's state. Address this by adding a new
rfork(2) flag, RFSPAWN, that has vfork(2) semantics but also resets signal
handlers in the child during creation.

x86 uses rfork_thread(3) instead of a direct rfork(2) because rfork with
RFMEM/RFSPAWN cannot work when the return address is stored on the stack --
further information about this problem is described under RFMEM in the
rfork(2) man page.

Addressing this has been identified as a prerequisite to using posix_spawn
in subprocess on FreeBSD [2].

[1] https://ewontfix.com/7/
[2] https://bugs.python.org/issue35823

MFC r348360:
Do not go into sleep in sleepq_catch_signals() when SIGSTOP from
PT_ATTACH was consumed.

PR: 231445

MFC r349320, r349324:
coredump: avoid writing to core files not owned by the effective user.

PR: 68905
admbugs: 358

MFC r342591,342599:

Make kernel print jail ID when logging a process exit

Kernel now includes jail ID when logging a process exit. jid is 0 for unjailed
processes.

Submitted by: Marie Helene Kvello-Aune <freebsd@mhka.no>
Relnotes: yes
Sponsored by: Modirum MDPay

MFC 341800: Don't report stale signal information in ptrace_lwpinfo.

Once a signal's siginfo was copied to 'td_si' as part of the signal
exchange in issignal(), it was never cleared. This caused future
thread events that are reported as SIGTRAP events without signal
information to report the stale siginfo in 'td_si'. For example, if a
debugger created a new process and used SIGSTOP to stop it after
PT_ATTACH, future system call entry / exit events would set PL_FLAG_SI
with the SIGSTOP siginfo in pl_siginfo. This broke 'catch syscall' in
current versions of gdb as it assumed PL_FLAG_SI with SIGTRAP
indicates a breakpoint or single step trap.

MFC r341094:
Improve sigonstack().

MFC r335844:

core(5): overwrite the oldest core dump

The '%I' format in the kern.corefile sysctl limits the number of
core files that a process can generate to the number stored in the
debug.ncores sysctl. The '%I' format is replaced by the single digit
index. Previously, if all indexes were taken the kernel would overwrite
only a core file with the highest index in a filename.
Currently the system will create a new core file if there is a free
index or if all slots are taken it will overwrite the oldest one.

Reviewed by: kib(code), bcr (updating)
Differential Revision: https://reviews.freebsd.org/D15991
Differential Revision: https://reviews.freebsd.org/D16084

MFC r337330:
Swap in WKILLED processes.

MFC r335504:
fork: avoid endless wait with PTRACE_FORK and RFSTOPPED.

MFC r331640:
Fix several leaks of kernel stack data through paddings.

Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

MFC r314568 (by emaste):

kern_sig.c: ANSIfy and remove archaic register keyword

Sponsored by: The FreeBSD Foundation

MFC r318389 (by emaste):

Remove register keyword from sys/ and ANSIfy prototypes

A long long time ago the register keyword told the compiler to store
the corresponding variable in a CPU register, but it is not relevant
for any compiler used in the FreeBSD world today.

ANSIfy related prototypes while here.

Reviewed by: cem, jhb
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D10193

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

MFC r324671:
Re-evaluate thread' signal mask after ptracestop().

MFC r316286:

Add support for capturing 'struct ptrace_lwpinfo' for signals resulting in a
process dumping core in the corefile.

Direct stable changed: Padding added to struct thread and td_si added to end
with explicit bzeroing when forking/initializing a thread to preserve KBI.

MFC r324670:
Improve assertion that an ignored or blocked signal is not delivered.

MFC r324669:
Style.

MFC r321627:
Make it possible to request nosys logging to console.

MFC r319874:
Print unimplemented syscall number to the ctty on SIGSYS, if enabled
by the knob kern.lognosys.

MFC r318191:
Let ptracestop() suspend threads sleeping in an SBDRY section.

MFC r318243:
Do not wake up sleeping thread in reschedule_signals() if the signal
is blocked. The spurious wakeup might result in spurious EINTR.

PR: 219228

MFC r317845-r317846

r317845:
Provide a freebsd32 implementation of sigqueue()

The previous misuse of sys_sigqueue() was sending random register or
stack garbage to 64-bit targets. The freebsd32 implementation preserves
the sival_int member of value when signaling a 64-bit process.

Document the mixed ABI implementation of union sigval and the
incompability of sival_ptr with pointer integrity schemes.

Reviewed by: kib, wblock
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D10605

r317846:
Regen post r317845.

MFC with: r317845
Sponsored by: DARPA, AFRL

MFC r315412, r314852:

r315412:
Don't clear p_ptevents on normal SIGKILL delivery

The ptrace() user has the option of discarding the signal. In such a
case, p_ptevents should not be modified. If the ptrace() user decides to
send a SIGKILL, ptevents will be cleared in ptracestop(). procfs events
do not have the capability to discard the signal, so continue to clear
the mask in that case.

r314852:
don't stop in issignal() if P_SINGLE_EXIT is set

Suppose a traced process is stopped in ptracestop() due to receipt of a
SIGSTOP signal, and is awaiting orders from the tracing process on how
to handle the signal. Before sending any such orders, the tracing
process exits. This should kill the traced process. But suppose a second
thread handles the SIGKILL and proceeds to exit1(), calling
thread_single(). The first thread will now awaken and will have a chance
to check once more if it should go to sleep due to the SIGSTOP. It must
not sleep after P_SINGLE_EXIT has been set; this would prevent the
SIGKILL from taking effect, leaving a stopped orphan behind after the
tracing process dies.

Also add new tests for this condition.

Sponsored by: Dell EMC

MFC r313992, r314075, r314118, r315484:

r315484:
ptrace_test: eliminate assumption about thread scheduling

A couple of the ptrace tests make assumptions about which thread in a
multithreaded process will run after a halt. This makes the tests less
portable across branches, and susceptible to future breakage. Instead,
twiddle thread scheduling and priorities to match the tests'
expectation.

r314118:
Actually fix buildworlds other than i386/amd64/sparc64 after r313992

Disable offending test for platforms without a userspace visible
breakpoint().

r314075:
Fix world build for archs where __builtin_debugtrap() does not work.

The offending code was introduced in r313992.

r313992:
Defer ptracestop() signals that cannot be delivered immediately

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
Sponsored by: Dell EMC

MFC r315453:
When clearing altsigstack settings on exec, do it to the right thread.

MFC r304440, r304487:
Fix some handling of P2_PTRACE_FSTP.

MFC r303423:
Force SIGSTOP to be the first signal reported after the attach.

MFC 302900,302902,302921,303461,304009:
Add a mask of optional ptrace() events.

302900:
Add a test for user signal delivery.

This test verifies we get the correct ptrace event details when a signal
is posted to a traced process from userland.

302902:
Add a mask of optional ptrace() events.

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.

302921:
Rename PTRACE_SYSCALL to LINUX_PTRACE_SYSCALL.

303461:
Note that not all optional ptrace events use SIGTRAP.

New child processes attached due to PTRACE_FORK use SIGSTOP instead of
SIGTRAP. All other ptrace events use SIGTRAP.

304009:
Remove description of P_FOLLOWFORK as this flag was removed.