This selects the THREAD_INFO_IN_TASK option for UM and changes the way
that the current task is discovered. This is trivial though, as UML
already tracks the current task in cpu_tasks[] and this can be used to
retrieve it.
Also remove the signal handler code that copies the thread information
into the IRQ stack. It is obsolete now, which also means that the
mentioned race condition cannot happen anymore.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Reviewed-by: Hajime Tazaki <thehajime@gmail.com>
Link: https://patch.msgid.link/20241111102910.46512-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The show_stack function had some code to detect double faults. However,
the logic is wrong and it would e.g. trigger if a WARNING happened
inside an IRQ.
Remove it without trying to add a new logic. The current behaviour,
which will just fault repeatedly until the IRQ stack is used up and the
host kills UML, seems to be good enough.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241103150506.1367695-5-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
There is no need to sync the stub code to "disk" for the other process
to see the correct memory. Drop the fsync there and remove the helper
function.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241103150506.1367695-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Since commit a95b37e20d ("kbuild: get <linux/compiler_types.h> out of
<linux/kconfig.h>") we can safely include these files in userspace code.
Doing so simplifies matters as options do not need to be exported via
asm-offsets.h anymore.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241103150506.1367695-2-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
There is no point in either dumping the KASAN shadow memory or doing
copy-on-write after a fork on these memory regions.
This considerably speeds up coredump generation.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241103150506.1367695-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The write_sigio thread is not really a traditional thread. Set
the parent-death signal for it to ensure that it will be killed
if the UML kernel dies unexpectedly without proper cleanup.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241024142828.2612828-4-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This helper can be used to set the parent-death signal of the calling
process to SIGKILL to ensure that the process will be killed if the
UML kernel dies unexpectedly without proper cleanup. This helper will
be used in the follow-up patches.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241024142828.2612828-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Evidently, PATH_MAX isn't always defined, at least not via <limits.h>.
Simply remove the use and replace it by a constant 4k. As stat::st_size
is zero for /proc/self/exe we can't even size it automatically, and it
seems unlikely someone's going to try to run UML with such a path.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410240553.gYNIXN8i-lkp@intel.com/
Fixes: 031acdcfb5 ("um: restore process name")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The PTRACE_GETREGSET API has now existed since Linux 2.6.33. The XSAVE
CPU feature should also be sufficiently common to be able to rely on it.
With this, define our internal FP state to be the hosts XSAVE data. Add
discovery for the hosts XSAVE size and place the FP registers at the end
of task_struct so that we can adjust the size at runtime.
Next we can implement the regset API on top and update the signal
handling as well as ptrace APIs to use them. Also switch coredump
creation to use the regset API and finally set HAVE_ARCH_TRACEHOOK.
This considerably improves the signal frames. Previously they might not
have contained all the registers (i386) and also did not have the
sizes and magic values set to the correct values to permit userspace to
decode the frame.
As a side effect, this will permit UML to run on hosts with newer CPU
extensions (such as AMX) that need even more register state.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241023094120.4083426-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
In time-travel mode userspace can do a lot of work without any time
passing. Unfortunately, this can result in OOM situations as the RCU
core code will never be run.
Work around this by keeping track of userspace processes that do not
yield for a lot of operations. When this happens, insert a jiffie into
the sched_clock clock to account time against the process and cause the
bookkeeping to run.
As sched_clock is used for tracing, it is useful to keep it in sync
between the different VMs. As such, try to remove added ticks again when
the actual clock ticks.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241010142537.1134685-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
When a PTE is updated in the page table, the _PAGE_NEWPAGE bit will
always be set. And the corresponding page will always be mapped or
unmapped depending on whether the PTE is present or not. The check
on the _PAGE_NEWPROT bit is not really reachable. Abandoning it will
allow us to simplify the code and remove the unreachable code.
Reviewed-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241011102354.1682626-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This parameter is UML specific and is unknown to kernel. It should not
be propagated to kernel, otherwise it could be passed to user space as
a command line option by kernel with a warning like:
Unknown kernel command line parameters "noreboot", will be passed to user space.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241011040441.1586345-6-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This parameter is UML specific and is unknown to kernel. It should not
be propagated to kernel, otherwise it will be passed to user space as
an environment option by kernel with a warning like:
Unknown kernel command line parameters "uml_dir=/foo", will be passed to user space.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20241011040441.1586345-4-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This was perhaps intended to do _nofault copies, but the
real reason is lost to history. Remove this, it's not
needed, and using longjmp() out of the middle of the
signal handler with all the state it has modified is
not going to be a good idea anyway.
Link: https://patch.msgid.link/20241010224513.901c4d390b3e.Ia74742668b44603c1ca23dd36f90e964e6e7ee55@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
After the execve() to disable ASLR, comm is now "exe",
which is a bit confusing. Use readlink() to get this
to the right name again.
Disable stack frame size warnings on main.o since it's
part of the initial userspace and can use larger stack.
Fixes: 68b9883cc1 ("um: Discover host_task_size from envp")
Link: https://patch.msgid.link/20241010161411.c576e2aeb3e5.I244d4f34b8a8555ee5bec0e1cf5027bce4cc491b@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
When loading the UML binary, the host kernel will place the stack at the
highest possible address. It will then map the program name and
environment variables onto the start of the stack.
As such, an easy way to figure out the host_task_size is to use the
highest pointer to an environment variable as a reference.
Ensure that this works by disabling address layout randomization and
re-executing UML in case it was enabled.
This increases the available TASK_SIZE for 64 bit UML considerably.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240919124511.282088-9-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Using clone will not undo features that have been enabled by libc. An
example of this already happening is rseq, which could cause the kernel
to read/write memory of the userspace process. In the future the
standard library might also use mseal by default to protect itself,
which would also thwart our attempts at unmapping everything.
Solve all this by taking a step back and doing an execve into a tiny
static binary that sets up the minimal environment required for the
stub without using any standard library. That way we have a clean
execution environment that is fully under the control of UML.
Note that this changes things a bit as the FDs are not anymore shared
with the kernel. Instead, we explicitly share the FDs for the physical
memory and all existing iomem regions. Doing this is fine, as iomem
regions cannot be added at runtime.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240919124511.282088-3-benjamin@sipsolutions.net
[use pipe() instead of pipe2(), remove unneeded close() calls]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
We do not need the extra save/restore of the FP registers when getting
the fault information. This was originally added in commit 2f56debd77
("uml: fix FP register corruption") but at that time the code was not
saving/restoring the FP registers when switching to userspace. This was
fixed in commit fbfe9c847e ("um: Save FPU registers between task
switches") and since then the auxiliary registers have not been useful.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20241004233821.2130874-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
high_physmem has already been declared in as-layout.h, so there is
no need to declare it explicitly in the .c file again.
While at it, group the declarations of __real_malloc and __real_free
together to make the code slightly more readable.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20240916045950.508910-2-tiwei.btw@antgroup.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
It's no longer used since the removal of the SKAS3/4 support.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
When generalizing this, I was in the mindset of this being
"userspace" code, but even there we should not use variable
arrays as the kernel is moving away from allowing that.
Simply reserve (but not use) enough space for the maximum
two descriptors we might need now, and return an error if
attempting to receive more than that.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407041459.3SYg4TEi-lkp@intel.com/
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Conceptually, we want the memory mappings to always be up to date and
represent whatever is in the TLB. To ensure that, we need to sync them
over in the userspace case and for the kernel we need to process the
mappings.
The kernel will call flush_tlb_* if page table entries that were valid
before become invalid. Unfortunately, this is not the case if entries
are added.
As such, change both flush_tlb_* and set_ptes to track the memory range
that has to be synchronized. For the kernel, we need to execute a
flush_tlb_kern_* immediately but we can wait for the first page fault in
case of set_ptes. For userspace in contrast we only store that a range
of memory needs to be synced and do so whenever we switch to that
process.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-13-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The HVC update was mostly used to compress consecutive calls into one.
This is mostly relevant for userspace where it is already handled by the
syscall stub code.
Simplify the whole logic and consolidate it for both kernel and
userspace. This does remove the sequential syscall compression for the
kernel, however that shouldn't be the main factor in most runs.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-12-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
As running the syscalls is expensive due to context switches, we should
do so as late as possible in case more syscalls need to be queued later
on. This will also benefit a later move to a SECCOMP enabled userspace
as in that case the need for extra context switches is removed entirely.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Link: https://patch.msgid.link/20240703134536.1161108-9-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The kernel flushes the memory ranges anyway for CoW and does not assume
that the userspace process has anything set up already. So, start with a
fresh process for the new mm context.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-8-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
The current LDT code has a few issues that mean it should be redone in a
different way once we always start with a fresh MM even when cloning.
In a new and better world, the kernel would just ensure its own LDT is
clear at startup. At that point, all that is needed is a simple function
to populate the LDT from another MM in arch_dup_mmap combined with some
tracking of the installed LDT entries for each MM.
Note that the old implementation was even incorrect with regard to
reading, as it copied out the LDT entries in the internal format rather
than converting them to the userspace structure.
Removal should be fine as the LDT is not used for thread-local storage
anymore.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-7-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
To keep the number of syscalls that the stub has to do lower, compress
two consecutive syscalls of the same type if the second is just a
continuation of the first.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-6-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Rework syscall handling to be platform independent. Also create a clean
split between queueing of syscalls and flushing them out, removing the
need to keep state in the code that triggers the syscalls.
The code adds syscall_data_len to the global mm_id structure. This will
be used later to allow surrounding code to track whether syscalls still
need to run and if errors occurred.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Link: https://patch.msgid.link/20240703134536.1161108-5-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
When we switch to use seccomp, we need both the signal stack and other
data (i.e. syscall information) to co-exist in the stub data. To
facilitate this, start by defining separate memory areas for the stack
and syscall data.
This moves the signal stack onto a new page as the memory area is not
sufficient to hold both signal stack and syscall information.
Only change the signal stack setup for now, as the syscall code will be
reworked later.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Link: https://patch.msgid.link/20240703134536.1161108-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
When signals are hard-blocked in order to do time-travel
socket processing, we set signals_blocked and then handle
SIGIO signals by setting the SIGIO bit in signals_pending.
When unblocking, we first set signals_blocked to 0, and
then handle all pending signals. We have to set it first,
so that we can again properly block/unblock inside the
unblock, if the time-travel handlers need to be processed.
Unfortunately, this is racy. We can get into this situation:
// signals_pending = SIGIO_MASK
unblock_signals_hard()
signals_blocked = 0;
if (signals_pending && signals_enabled) {
block_signals();
unblock_signals()
...
sig_handler_common(SIGIO, NULL, NULL);
sigio_handler()
...
sigio_reg_handler()
irq_do_timetravel_handler()
reg->timetravel_handler() ==
vu_req_interrupt_comm_handler()
vu_req_read_message()
vhost_user_recv_req()
vhost_user_recv()
vhost_user_recv_header()
// reads 12 bytes header of
// 20 bytes message
<-- receive SIGIO here <--
sig_handler()
int enabled = signals_enabled; // 1
if ((signals_blocked || !enabled) && (sig == SIGIO)) {
if (!signals_blocked && time_travel_mode == TT_MODE_EXTERNAL)
sigio_run_timetravel_handlers()
_sigio_handler()
sigio_reg_handler()
... as above ...
vhost_user_recv_header()
// reads 8 bytes that were message payload
// as if it were header - but aborts since
// it then gets -EAGAIN
...
--> end signal handler -->
// continue in vhost_user_recv()
// full_read() for 8 bytes payload busy loops
// entire process hangs here
Conceptually, to fix this, we need to ensure that the
signal handler cannot run while we hard-unblock signals.
The thing that makes this more complex is that we can be
doing hard-block/unblock while unblocking. Introduce a
new signals_blocked_pending variable that we can keep at
non-zero as long as pending signals are being processed,
then we only need to ensure it's decremented safely and
the signal handler will only increment it if it's already
non-zero (or signals_blocked is set, of course.)
Note also that only the outermost call to hard-unblock is
allowed to decrement signals_blocked_pending, since it
could otherwise reach zero in an inner call, and leave
the same race happening if the timetravel_handler loops,
but that's basically required of it.
Fixes: d6b399a0e0 ("um: time-travel/signals: fix ndelay() in interrupt")
Link: https://patch.msgid.link/20240703110144.28034-2-johannes@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Add a message type to the time-travel protocol to broadcast
a small (64-bit) value to all participants in a simulation.
The main use case is to have an identical message come to
all participants in a simulation, e.g. to separate out logs
for different tests running in a single simulation.
Down in the guts of time_travel_handle_message() we can't
use printk() and not even printk_deferred(), so just store
the message and print it at the start of the userspace()
function.
Unfortunately this means that other prints in the kernel
can actually bypass the message, but in most cases where
this is used, for example to separate test logs, userspace
will be involved. Also, even if we could use
printk_deferred(), we'd still need to flush it out in the
userspace() function since otherwise userspace messages
might cross it.
As a result, this is a reasonable compromise, there's no
need to have any core changes and it solves the main use
case we have for it.
Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Link: https://patch.msgid.link/20240702192118.c4093bc5b15e.I2ca8d006b67feeb866ac2017af7b741c9e06445a@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
When in time-travel mode (infinite-cpu or external) time should not pass
for writing to the console. As such, it makes sense to put the FD for
the output side into blocking mode and simply let any write to it hang.
If we did not do this, then time could pass waiting for the console to
become writable again. This is not desirable as it has random effects on
the clock between runs.
Implement this by duplicating the FD if output is active in a relevant
mode and setting the duplicate to be blocking. This avoids changing the
input channel to be blocking should it exists. After this, use the
blocking FD for all write operations and do not allocate an IRQ it is
set.
Without time-travel mode fd_out will always match fd_in and IRQs are
registered.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20231018123643.1255813-4-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Move relevant declarations to this header. This will address
below -Wmissing-prototypes warnings:
arch/um/os-Linux/elf_aux.c:26:13: warning: no previous prototype for ‘scan_elf_aux’ [-Wmissing-prototypes]
arch/um/os-Linux/mem.c:213:13: warning: no previous prototype for ‘check_tmpexec’ [-Wmissing-prototypes]
arch/um/os-Linux/skas/process.c:107:6: warning: no previous prototype for ‘wait_stub_done’ [-Wmissing-prototypes]
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
Make it match its definition (size_t vs unsigned long). And declare
it in a shared header to fix the -Wmissing-prototypes warning, as it
is defined in the user code and called in the kernel code.
Fixes: 5b301409e8 ("UML: add support for KASAN under x86_64")
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
These functions are not called explicitly. Let's just workaround
the -Wmissing-prototypes warnings by declaring them locally similar
to what was done in arch/x86/kernel/asm-offsets_32.c.
This will address below -Wmissing-prototypes warnings:
./arch/x86/um/shared/sysdep/kernel-offsets.h:9:6: warning: no previous prototype for ‘foo’ [-Wmissing-prototypes]
arch/um/os-Linux/main.c:187:7: warning: no previous prototype for ‘__wrap_malloc’ [-Wmissing-prototypes]
arch/um/os-Linux/main.c:208:7: warning: no previous prototype for ‘__wrap_calloc’ [-Wmissing-prototypes]
arch/um/os-Linux/main.c:222:6: warning: no previous prototype for ‘__wrap_free’ [-Wmissing-prototypes]
arch/x86/um/user-offsets.c:17:6: warning: no previous prototype for ‘foo’ [-Wmissing-prototypes]
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This will address below -Wmissing-prototypes warnings:
arch/um/kernel/initrd.c:18:12: warning: no previous prototype for ‘read_initrd’ [-Wmissing-prototypes]
arch/um/kernel/um_arch.c:408:19: warning: no previous prototype for ‘read_initrd’ [-Wmissing-prototypes]
arch/um/os-Linux/start_up.c:301:12: warning: no previous prototype for ‘parse_iomem’ [-Wmissing-prototypes]
arch/x86/um/ptrace_32.c:15:6: warning: no previous prototype for ‘arch_switch_to’ [-Wmissing-prototypes]
arch/x86/um/ptrace_32.c:101:5: warning: no previous prototype for ‘poke_user’ [-Wmissing-prototypes]
arch/x86/um/ptrace_32.c:153:5: warning: no previous prototype for ‘peek_user’ [-Wmissing-prototypes]
arch/x86/um/ptrace_64.c:111:5: warning: no previous prototype for ‘poke_user’ [-Wmissing-prototypes]
arch/x86/um/ptrace_64.c:171:5: warning: no previous prototype for ‘peek_user’ [-Wmissing-prototypes]
arch/x86/um/syscalls_64.c:48:6: warning: no previous prototype for ‘arch_switch_to’ [-Wmissing-prototypes]
arch/x86/um/tls_32.c:184:5: warning: no previous prototype for ‘arch_switch_tls’ [-Wmissing-prototypes]
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
This will also fix the warnings like:
warning: no previous prototype for ‘fork_handler’ [-Wmissing-prototypes]
140 | void fork_handler(void)
| ^~~~~~~~~~~~
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
The ARCH=um build has its own idea about strscpy()'s definition. Adjust
the callers to remove the redundant sizeof() arguments ahead of treewide
changes, since it needs a manual adjustment for the newly named
sized_strscpy() export.
Cc: Richard Weinberger <richard@nod.at>
Cc: linux-um@lists.infradead.org
Signed-off-by: Kees Cook <keescook@chromium.org>
These functions were only used when calling PTRACE_ARCH_PRCTL, but this
code has been removed.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
The trampoline is running in a cloned process. It is not safe to use
printk for error printing there.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
The threads allocated inside the kernel have only a single page of
stack. Unfortunately, the vfprintf function in standard glibc may use
too much stack-space, overflowing it.
To make os_info safe to be used by helper threads, use the kernel
vscnprintf function into a smallish buffer and write out the information
to stderr.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
For the detection code to check whether SYSEMU_SINGLESTEP works
correctly we needed some error cases while stopping to be non-fatal.
However, at this point stop_ptraced_child must always succeed, and we
can therefore simplify it slightly to exit immediately on error.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
start_userspace is only called from exactly one location, and the passed
pointer for the userspace process stack cannot be NULL.
Remove the check, without changing the control flow.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Richard Weinberger <richard@nod.at>
These features have existed since Linux 2.6.14 and can be considered
widely available at this point. Also drop the backward compatibility
code for PTRACE_SETOPTIONS.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
----
v2:
* Continue to define PTRACE_SYSEMU_SINGLESTEP as glibc only added it in
version 2.27.
Signed-off-by: Richard Weinberger <richard@nod.at>
