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Since first moving __init text into the right place in commit
8966ed0b2d48 ("um: move init text between __init_begin/end")
and then making all init sections inaccessible, shutdown and
reboot crash instead of working correctly, for the obvious
reason that the functions are __init but run on the way out.
Removing the __init markers would work in some way, but that
would bubble through a lot of functions.
Instead, mark the relevant functions __noreturn (including
longjmp() since that's now needed so start_idle_thread() can
be __noreturn), and split out the part of main() that's done
on the way out into a new os_exit() function that's called
directly.
Reported-by: Hajime Tazaki <thehajime@gmail.com>
Closes: https://lore.kernel.org/linux-um/m24ifc4v6m.wl-thehajime@gmail.com/
Fixes: a418ab8fddea ("um: mprotect() __init memory")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Tested-by: Hajime Tazaki <thehajime@gmail.com>
Link: https://patch.msgid.link/20260928093934.ca7af44c59ca.I470ece16d176ea704aa6e5767b755055d106da35@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Just incrementing tt_extra_sched_jiffies can make this
drift enough to hit the softlockup detector, e.g. with
ping using sched_yield() in a loop to measure short
intervals. Make the simulation actually pass time, this
requires going to the external scheduler but actually
makes this sort of thing behave much better and avoids
the soft lockup.
Fixes: 887c5c12e80c ("um: work around sched_yield not yielding in time-travel mode")
Link: https://patch.msgid.link/20260924134223.1672004-2-johannes@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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With clang, stub compilation could result in getting stack
frames where none are allowed, or ways of making it be not
relocatable. Set -ftrivial-auto-var-init=uninitialized for
more code, and -fomit-frame-pointer as well to avoid these
issues.
Link: https://patch.msgid.link/20260923173523.9cb03214335b.Ie1487657bc0f464f4911e95f532ab010b32864b8@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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For NOMMU there are not separate address spaces for
each userspace process group, which on the one hand
means we cannot start them on demand, but on the
other means we can just have one for each (virtual)
CPU, and map all of the memory into them.
Implement such processes, and the remaining bits
needed to compile the kernel without CONFIG_MMU.
Link: https://patch.msgid.link/20260723113633.2184dce9413e.I9f810f3ed177d6dc980cad36c231f8c745dee48f@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Since this approach shares more code with the MMU version
in nommu, further move some code around to be able to use
it in nommu (report_enomem) or be able to replace it (this
applies to mm_id, stack, sync). Also add empty inlines for
the TLB flushing and decouple trap.c code.
Link: https://patch.msgid.link/20260723113633.163686eb0863.Ibb7f37d5645cbd566ae5b74fbb19c54c7327ba68@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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The futex operations are both now wrong, neither have proper
atomic semantics, which are needed for SMP. Even if we don't
have SMP across threads of a process yet, multiple processes
can use futexes to synchronize.
Also remove the documentation that's duplicated (and wrong,
as this implementation never returns -EAGAIN).
Acked-By: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Link: https://patch.msgid.link/20260723113137.9f16fc4d0c83.I76c3b1c4de6591fa277db8da39e5a24a62361694@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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The return value of __secure_computing() currently uses 0 to indicate
that a system call should be allowed, and -1 to indicate that it should
be blocked/killed. This 0/-1 pattern is non-intuitive for a security
check function and makes the control flow at the call sites less readable.
Furthermore, any potential future changes to these return values would
require a high-risk, error-prone audit of all its users across different
architectures.
Sanitize this logic by converting the return type of __secure_computing()
to a proper boolean, where 'true' explicitly means 'allow' and 'false'
means 'fail/deny'.
Update all the two dozen or so call sites across the tree to align with
this new boolean semantic. No functional changes are intended, as the
callers still return -1 to the lower-level assembly entry code upon
seccomp denial.
Rename the function to __seccomp_permit_syscall() so that the purpose is
entirely clear.
[ tglx: Rename the function ]
Suggested-by: Thomas Gleixner <tglx@kernel.org>
Suggested-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Thomas Gleixner <tglx@kernel.org>
Tested-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
Reviewed-by: Mukesh Kumar Chaurasiya (IBM) <mkchauras@gmail.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Link: https://patch.msgid.link/20260707190254.230735780@kernel.org
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strncpy_chunk_from_user()
Replace the deprecated[1] strncpy() with strnlen() on the source
followed by memcpy_and_pad().
This function is a chunk callback for UML's strncpy_from_user()
implementation, called by buffer_op() to process userspace memory one
page at a time. The source is a kernel-mapped userspace address that
is not guaranteed to be NUL-terminated; "len" bounds how many bytes
to read from it.
By measuring the source string length first with strnlen(), we avoid
reading past the NUL terminator in the source. memcpy_and_pad() then
copies the string content and zero-fills the remainder of the chunk,
preserving the original strncpy() behavior exactly: copy up to the
first NUL, then pad with zeros to the full length.
strtomem_pad() would be the idiomatic helper for this strnlen() +
memcpy_and_pad() pattern, but it requires a compile-time-determinable
destination size (via ARRAY_SIZE()). Here the destination is a char *
into a caller-provided buffer and the chunk length is a runtime value,
so the explicit two-step is necessary.
No behavioral change: the same bytes are written to the destination
(string content followed by zero padding), the pointer advances by
the same amount, and the NUL-found return condition is unchanged.
Link: https://github.com/KSPP/linux/issues/90 [1]
Signed-off-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/20260323171713.work.839-kees@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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The UML stub takes the address of CMSG_DATA(fd_msg):
fd_map = (void *)&CMSG_DATA(fd_msg);
CMSG_DATA() is specified by POSIX to return unsigned char *. Taking
its address is semantically wrong -- the intent is to get a pointer
to the control message data, which is exactly what CMSG_DATA()
already returns.
This happens to compile with glibc because glibc's primary
CMSG_DATA definition accesses a flexible array member:
#define CMSG_DATA(cmsg) ((cmsg)->__cmsg_data)
An array lvalue can have its address taken, and &array yields the
same address as array. However, glibc also has an alternative
definition that uses pointer arithmetic (returning an rvalue), and
musl's definition always uses pointer arithmetic:
/* musl */
#define CMSG_DATA(cmsg) \
((unsigned char *)(((struct cmsghdr *)(cmsg)) + 1))
Taking the address of an rvalue is a hard error in C, so the
current code fails to compile with musl libc.
Remove the erroneous & operator. The resulting code is correct
regardless of the CMSG_DATA implementation -- it simply assigns the
data pointer, which is what the subsequent code (fd_map[--num_fds])
expects.
No functional change with glibc; fixes the build with musl.
Signed-off-by: Marcel W. Wysocki <maci.stgn@gmail.com>
Link: https://patch.msgid.link/20260215142803.1455757-1-maci.stgn@gmail.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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With Clang's context analysis, the compiler is a bit more strict about
what goes into the __acquires/__releases annotations and can't refer to
non-existent variables.
On an UM build, mm_id.h is transitively included into mm_types.h, and we
can observe the following error (if context analysis is enabled in e.g.
stackdepot.c):
In file included from lib/stackdepot.c:17:
In file included from include/linux/debugfs.h:15:
In file included from include/linux/fs.h:5:
In file included from include/linux/fs/super.h:5:
In file included from include/linux/fs/super_types.h:7:
In file included from include/linux/list_lru.h:14:
In file included from include/linux/xarray.h:16:
In file included from include/linux/gfp.h:7:
In file included from include/linux/mmzone.h:22:
In file included from include/linux/mm_types.h:26:
In file included from arch/um/include/asm/mmu.h:12:
>> arch/um/include/shared/skas/mm_id.h:24:54: error: use of undeclared identifier 'turnstile'
24 | void enter_turnstile(struct mm_id *mm_id) __acquires(turnstile);
| ^~~~~~~~~
arch/um/include/shared/skas/mm_id.h:25:53: error: use of undeclared identifier 'turnstile'
25 | void exit_turnstile(struct mm_id *mm_id) __releases(turnstile);
| ^~~~~~~~~
One (discarded) option was to use token_context_lock(turnstile) to just
define a token with the already used name, but that would not allow the
compiler to distinguish between different mm_id-dependent instances.
Another constraint is that struct mm_id is only declared and incomplete
in the header, so even if we tried to construct an expression to get to
the mutex instance, this would fail (including more headers transitively
everywhere should also be avoided).
Instead, just declare an mm_id-dependent helper to return the mutex, and
use the mm_id-dependent call expression in the __acquires/__releases
attributes; the compiler will consider the identity of the mutex to be
the call expression. Then using __get_turnstile() in the lock/unlock
wrappers (with context analysis enabled for mmu.c) the compiler will be
able to verify the implementation of the wrappers as-is.
We leave context analysis disabled in arch/um/kernel/skas/ for now. This
change is a preparatory change to allow enabling context analysis in
subsystems that include any of the above headers.
No functional change intended.
Closes: https://lore.kernel.org/oe-kbuild-all/202512171220.vHlvhpCr-lkp@intel.com/
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20251219154418.3592607-23-elver@google.com
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Add initial symmetric multi-processing (SMP) support to UML. With
this support enabled, users can tell UML to start multiple virtual
processors, each represented as a separate host thread.
In UML, kthreads and normal threads (when running in kernel mode)
can be scheduled and executed simultaneously on different virtual
processors. However, the userspace code of normal threads still
runs within their respective single-threaded stubs.
That is, SMP support is currently available both within the kernel
and across different processes, but still remains limited within
threads of the same process in userspace.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20251027001815.1666872-6-tiwei.bie@linux.dev
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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The PID of the stub process can be obtained from current_mm_id().
There is no need to track it via userspace_pid[]. Stop doing that
to simplify the code.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20250711065021.2535362-4-tiwei.bie@linux.dev
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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They are only used within mmu.c. Make them static.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Link: https://patch.msgid.link/20250708090403.1067440-3-tiwei.bie@linux.dev
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Since Thomas's recent commit 2af10530639b ("um/x86: Add
system call table to header file") , we now have two
extern declarations of the syscall table, one internal
and one external, and they don't even match on 32-bit.
Clean this up and remove all the extra code.
Reviewed-by: Thomas Weißschuh <thomas.weissschuh@linutronix.de>
Link: https://patch.msgid.link/20250704141243.a68366f6acc3.If8587a4aafdb90644fc6d0b2f5e31a2d1887915f@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Instead of always sharing the FDs with the userspace process, only hand
over the FDs needed for mmap when required. The idea is that userspace
might be able to force the stub into executing an mmap syscall, however,
it will not be able to manipulate the control flow sufficiently to have
access to an FD that would allow mapping arbitrary memory.
Security wise, we need to be sure that only the expected syscalls are
executed after the kernel sends FDs through the socket. This is
currently not the case, as userspace can trivially jump to the
rt_sigreturn syscall instruction to execute any syscall that the stub is
permitted to do. With this, it can trick the kernel to send the FD,
which in turn allows userspace to freely map any physical memory.
As such, this is currently *not* secure. However, in principle the
approach should be fine with a more strict SECCOMP filter and a careful
review of the stub control flow (as userspace can prepare a stack). With
some care, it is likely possible to extend the security model to SMP if
desired.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250602130052.545733-8-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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This adds the kernel side of the seccomp based process handling.
Co-authored-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250602130052.545733-6-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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When in seccomp mode, we would hang forever on the futex if a child has
died unexpectedly. In contrast, ptrace mode will notice it and kill the
corresponding thread when it fails to run it.
Fix this issue using a new IRQ that is fired after a SIGCHLD and keeping
an (internal) list of all MMs. In the IRQ handler, find the affected MM
and set its PID to -1 as well as the futex variable to FUTEX_IN_KERN.
This, together with futex returning -EINTR after the signal is
sufficient to implement a race-free detection of a child dying.
Note that this also enables IRQ handling while starting a userspace
process. This should be safe and SECCOMP requires the IRQ in case the
process does not come up properly.
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250602130052.545733-5-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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This adds the stub side for the new seccomp process management code. In
this case we do register save/restore through the signal handler
mcontext.
Add special code for handling TLS, which for x86_64 means setting the
FS_BASE/GS_BASE registers while for i386 it means calling the
set_thread_area syscall.
Co-authored-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Benjamin Berg <benjamin@sipsolutions.net>
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250602130052.545733-3-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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sched_yield by a userspace may not actually cause scheduling in
time-travel mode as no time has passed. In the case seen it appears to
be a badly implemented userspace spinlock in ASAN. Unfortunately, with
time-travel it causes an extreme slowdown or even deadlock depending on
the kernel configuration (CONFIG_UML_MAX_USERSPACE_ITERATIONS).
Work around it by accounting time to the process whenever it executes a
sched_yield syscall.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20250314130815.226872-1-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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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>
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free_pages() performs a parameter null check inside
therefore remove double zero check here.
Signed-off-by: Shaojie Dong <quic_shaojied@quicinc.com>
Link: https://patch.msgid.link/20241025-upstream_branch-v5-1-b8998beb2c64@quicinc.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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CONFIG_GCOV is special and only in UML since it builds the
kernel with a "userspace" option. This is fine, but the stub
is even more special and not really a full userspace process,
so it then fails to link as reported.
Remove the GCOV options from the stub build.
For good measure, also remove the GPROF options, even though
they don't seem to cause build failures now.
To be able to do this, export the specific options (GCOV_OPT
and GPROF_OPT) but rename them so there's less chance of any
conflicts.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202410242238.SXhs2kQ4-lkp@intel.com/
Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Link: https://patch.msgid.link/20241025102700.9fbb9c34473f.I7f1537fe075638f8da64beb52ef6c9e5adc51bc3@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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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>
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Since __attribute__((naked)) cannot be used with functions
containing C statements, just generate the few instructions
it needs in assembly directly.
While at it, fix the stack usage ("1 + 2*x - 1" is odd) and
document what it must do, and why it must adjust the stack.
Fixes: 8508a5e0e9db ("um: Fix misaligned stack in stub_exe")
Link: https://lore.kernel.org/linux-um/CABVgOSntH-uoOFMP5HwMXjx_f1osMnVdhgKRKm4uz6DFm2Lb8Q@mail.gmail.com/
Reviewed-by: David Gow <davidgow@google.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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The stub_exe could segfault when built with some compilers (e.g. gcc
13.2.0), as SSE instructions which relied on stack alignment could be
generated, but the stack was misaligned.
This seems to be due to the __start entry point being run with a 16-byte
aligned stack, but the x86_64 SYSV ABI wanting the stack to be so
aligned _before_ a function call (so it is misaligned when the function
is entered due to the return address being pushed). The function
prologue then realigns it. Because the entry point is never _called_,
and hence there is no return address, the prologue is therefore actually
misaligning it, and causing the generated movaps instructions to
SIGSEGV. This results in the following error:
start_userspace : expected SIGSTOP, got status = 139
Don't generate this prologue for __start by using
__attribute__((naked)), which resolves the issue.
Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Signed-off-by: David Gow <davidgow@google.com>
Link: https://lore.kernel.org/linux-um/CABVgOS=boUoG6=LHFFhxEd8H8jDP1zOaPKFEjH+iy2n2Q5S2aQ@mail.gmail.com/
Link: https://patch.msgid.link/20241017231007.1500497-2-davidgow@google.com
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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When automatic variable initialization is enabled via
CONFIG_INIT_STACK_ALL_{PATTERN,ZERO}, clang will insert a call to
memset() to initialize an object created with __builtin_alloca(). This
ultimately breaks the build when linking stub_exe because it is a
standalone executable that does not include or link against memset().
ld: arch/um/kernel/skas/stub_exe.o: in function `_start':
arch/um/kernel/skas/stub_exe.c:83:(.ltext+0x15): undefined reference to `memset'
Disable automatic variable initialization for stub_exe.c by passing the
default value of 'uninitialized' to '-ftrivial-auto-var-init', which
avoids generating the call to memset(). This code is small and runs
quickly as it is just designed to set up an environment, so stack
variable initialization is unnecessary overhead for little gain.
Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20241016-uml-fix-stub_exe-clang-v1-2-3d6381dc5a78@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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When building stub_exe with clang, there is an error because '-n' is not
a recognized flag by the clang driver (which is being used to invoke the
linker):
clang: error: unknown argument: '-n'
'-n' should be passed along to the linker, as it is the short flag for
'--nmagic', so prefix it with '-Wl,'.
Fixes: 32e8eaf263d9 ("um: use execveat to create userspace MMs")
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Link: https://patch.msgid.link/20241016-uml-fix-stub_exe-clang-v1-1-3d6381dc5a78@kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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With the change to use execve() we can now safely clear the memory up to
STUB_START as rseq will not be trying to use memory in that region. Also,
on 64 bit the previous changes should mean that there is no usable
memory range above the stub.
Make the change and remove the comment as it is not needed anymore.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240919124511.282088-10-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Enable PR_SET_PDEATHSIG so that the UML userspace process will be killed
when the kernel exits unexpectedly.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240919124511.282088-4-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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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>
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The schedule() call there really never did anything at
least since the introduction of the EEVDF scheduler,
but now I found a case where we permanently hang in a
loop of -ERESTARTNOINTR (due to locking.) Work around
it by making any syscalls with error return take time
(and then schedule after) so we cannot hang in such a
loop forever.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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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>
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These fields are no longer used since the removal of tt mode.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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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>
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There should be no need to flush the memory in flush_thread. Doing this
likely worked around some issue where memory was still incorrectly
mapped when creating or cloning an MM.
With the removal of the special clone path, that isn't relevant anymore.
However, add the flush into MM initialization so that any new userspace
MM is guaranteed to be clean.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Link: https://patch.msgid.link/20240703134536.1161108-10-benjamin@sipsolutions.net
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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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>
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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>
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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>
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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>
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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>
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The host PID tracked in 'cpu_tasks' is no longer used. Stopping
tracking it will also save some cycles.
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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This will address below -Wmissing-prototypes warnings:
arch/um/kernel/mem.c:202:8: warning: no previous prototype for ‘pgd_alloc’ [-Wmissing-prototypes]
arch/um/kernel/mem.c:215:7: warning: no previous prototype for ‘uml_kmalloc’ [-Wmissing-prototypes]
arch/um/kernel/process.c:207:6: warning: no previous prototype for ‘arch_cpu_idle’ [-Wmissing-prototypes]
arch/um/kernel/process.c:328:15: warning: no previous prototype for ‘arch_align_stack’ [-Wmissing-prototypes]
arch/um/kernel/reboot.c:45:6: warning: no previous prototype for ‘machine_restart’ [-Wmissing-prototypes]
arch/um/kernel/reboot.c:51:6: warning: no previous prototype for ‘machine_power_off’ [-Wmissing-prototypes]
arch/um/kernel/reboot.c:57:6: warning: no previous prototype for ‘machine_halt’ [-Wmissing-prototypes]
arch/um/kernel/skas/mmu.c:17:5: warning: no previous prototype for ‘init_new_context’ [-Wmissing-prototypes]
arch/um/kernel/skas/mmu.c:60:6: warning: no previous prototype for ‘destroy_context’ [-Wmissing-prototypes]
arch/um/kernel/skas/process.c:36:12: warning: no previous prototype for ‘start_uml’ [-Wmissing-prototypes]
arch/um/kernel/time.c:807:15: warning: no previous prototype for ‘calibrate_delay_is_known’ [-Wmissing-prototypes]
arch/um/kernel/tlb.c:594:6: warning: no previous prototype for ‘force_flush_all’ [-Wmissing-prototypes]
arch/x86/um/bugs_32.c:22:6: warning: no previous prototype for ‘arch_check_bugs’ [-Wmissing-prototypes]
arch/x86/um/bugs_32.c:44:6: warning: no previous prototype for ‘arch_examine_signal’ [-Wmissing-prototypes]
arch/x86/um/bugs_64.c:9:6: warning: no previous prototype for ‘arch_check_bugs’ [-Wmissing-prototypes]
arch/x86/um/bugs_64.c:13:6: warning: no previous prototype for ‘arch_examine_signal’ [-Wmissing-prototypes]
arch/x86/um/elfcore.c:10:12: warning: no previous prototype for ‘elf_core_extra_phdrs’ [-Wmissing-prototypes]
arch/x86/um/elfcore.c:15:5: warning: no previous prototype for ‘elf_core_write_extra_phdrs’ [-Wmissing-prototypes]
arch/x86/um/elfcore.c:42:5: warning: no previous prototype for ‘elf_core_write_extra_data’ [-Wmissing-prototypes]
arch/x86/um/elfcore.c:63:8: warning: no previous prototype for ‘elf_core_extra_data_size’ [-Wmissing-prototypes]
arch/x86/um/fault.c:18:5: warning: no previous prototype for ‘arch_fixup’ [-Wmissing-prototypes]
arch/x86/um/os-Linux/mcontext.c:7:6: warning: no previous prototype for ‘get_regs_from_mc’ [-Wmissing-prototypes]
arch/x86/um/os-Linux/tls.c:22:6: warning: no previous prototype for ‘check_host_supports_tls’ [-Wmissing-prototypes]
Signed-off-by: Tiwei Bie <tiwei.btw@antgroup.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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arch_futex_atomic_op_inuser was not documented correctly
resulting in build time warnings.
Signed-off-by: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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There's a lot of code here that hard-codes that the
data is a single page, and right now that seems to
be sufficient, but to make it easier to change this
in the future, add a new STUB_DATA_PAGES constant
and use it throughout the code.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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I added $(srctree)/ to some included Makefiles in the following commits:
- 3204a7fb98a3 ("kbuild: prefix $(srctree)/ to some included Makefiles")
- d82856395505 ("kbuild: do not require sub-make for separate output tree builds")
They were a preparation for removing --include-dir flag.
I have never thought --include-dir useful. Rather, it _is_ harmful.
For example, run the following commands:
$ make -s ARCH=x86 mrproper defconfig
$ make ARCH=arm O=foo dtbs
make[1]: Entering directory '/tmp/linux/foo'
HOSTCC scripts/basic/fixdep
Error: kernelrelease not valid - run 'make prepare' to update it
UPD include/config/kernel.release
make[1]: Leaving directory '/tmp/linux/foo'
The first command configures the source tree for x86. The next command
tries to build ARM device trees in the separate foo/ directory - this
must stop because the directory foo/ has not been configured yet.
However, due to --include-dir=$(abs_srctree), the top Makefile includes
the wrong include/config/auto.conf from the source tree and continues
building. Kbuild traverses the directory tree, but of course it does
not work correctly. The Error message is also pointless - 'make prepare'
does not help at all for fixing the issue.
This commit fixes more arch Makefile, and finally removes --include-dir
from the top Makefile.
There are more breakages under drivers/, but I do not volunteer to fix
them all. I just moved --include-dir to drivers/Makefile.
With this commit, the second command will stop with a sensible message.
$ make -s ARCH=x86 mrproper defconfig
$ make ARCH=arm O=foo dtbs
make[1]: Entering directory '/tmp/linux/foo'
SYNC include/config/auto.conf.cmd
***
*** The source tree is not clean, please run 'make ARCH=arm mrproper'
*** in /tmp/linux
***
make[2]: *** [../Makefile:646: outputmakefile] Error 1
/tmp/linux/Makefile:770: include/config/auto.conf.cmd: No such file or directory
make[1]: *** [/tmp/linux/Makefile:793: include/config/auto.conf.cmd] Error 2
make[1]: Leaving directory '/tmp/linux/foo'
make: *** [Makefile:226: __sub-make] Error 2
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking updates from Borislav Petkov:
"Lots of cleanups and preparation. Highlights:
- futex: Cleanup and remove runtime futex_cmpxchg detection
- rtmutex: Some fixes for the PREEMPT_RT locking infrastructure
- kcsan: Share owner_on_cpu() between mutex,rtmutex and rwsem and
annotate the racy owner->on_cpu access *once*.
- atomic64: Dead-Code-Elemination"
[ Description above by Peter Zijlstra ]
* tag 'locking_core_for_v5.17_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking/atomic: atomic64: Remove unusable atomic ops
futex: Fix additional regressions
locking: Allow to include asm/spinlock_types.h from linux/spinlock_types_raw.h
x86/mm: Include spinlock_t definition in pgtable.
locking: Mark racy reads of owner->on_cpu
locking: Make owner_on_cpu() into <linux/sched.h>
lockdep/selftests: Adapt ww-tests for PREEMPT_RT
lockdep/selftests: Skip the softirq related tests on PREEMPT_RT
lockdep/selftests: Unbalanced migrate_disable() & rcu_read_lock().
lockdep/selftests: Avoid using local_lock_{acquire|release}().
lockdep: Remove softirq accounting on PREEMPT_RT.
locking/rtmutex: Add rt_mutex_lock_nest_lock() and rt_mutex_lock_killable().
locking/rtmutex: Squash self-deadlock check for ww_rt_mutex.
locking: Remove rt_rwlock_is_contended().
sched: Trigger warning if ->migration_disabled counter underflows.
futex: Fix sparc32/m68k/nds32 build regression
futex: Remove futex_cmpxchg detection
futex: Ensure futex_atomic_cmpxchg_inatomic() is present
kernel/locking: Use a pointer in ww_mutex_trylock().
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Remove address space overrides using set_fs() for User Mode Linux.
Note that just like the existing kernel access case of the uaccess
routines the new nofault kernel handlers do not actually have any
exception handling. This is probably broken, but not change to the
status quo.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Richard Weinberger <richard@nod.at>
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Now that all architectures have a working futex implementation in any
configuration, remove the runtime detection code.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Acked-by: Vineet Gupta <vgupta@kernel.org>
Acked-by: Max Filippov <jcmvbkbc@gmail.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Link: https://lore.kernel.org/r/20211026100432.1730393-2-arnd@kernel.org
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git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml
Pull UML updates from Richard Weinberger:
- Support for VMAP_STACK
- Support for splice_write in hostfs
- Fixes for virt-pci
- Fixes for virtio_uml
- Various fixes
* tag 'for-linus-5.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml:
um: fix stub location calculation
um: virt-pci: fix uapi documentation
um: enable VMAP_STACK
um: virt-pci: don't do DMA from stack
hostfs: support splice_write
um: virtio_uml: fix memory leak on init failures
um: virtio_uml: include linux/virtio-uml.h
lib/logic_iomem: fix sparse warnings
um: make PCI emulation driver init/exit static
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In commit 9f0b4807a44f ("um: rework userspace stubs to not hard-code
stub location") I changed stub_segv_handler() to do a calculation with
a pointer to a stack variable to find the data page that we're using
for the stack and the rest of the data. This same commit was meant to
do it as well for stub_clone_handler(), but the change inadvertently
went into commit 84b2789d6115 ("um: separate child and parent errors
in clone stub") instead.
This was reported to not be compiled correctly by gcc 5, causing the
code to crash here. I'm not sure why, perhaps it's UB because the var
isn't initialized? In any case, this trick always seemed bad, so just
create a new inline function that does the calculation in assembly.
Reported-by: subashab@codeaurora.org
Fixes: 9f0b4807a44f ("um: rework userspace stubs to not hard-code stub location")
Fixes: 84b2789d6115 ("um: separate child and parent errors in clone stub")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Richard Weinberger <richard@nod.at>
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