Commit ee3d9bd4de ("uml: simplify SIGSEGV
handling"), while greatly simplifying the kernel SIGSEGV handler that
runs in the process address space, introduced a bug which corrupts FP
state in the process.
Previously, the SIGSEGV handler called the sigreturn system call by hand - it
couldn't return through the restorer provided to it because that could try to
call the libc restorer which likely wouldn't exist in the process address
space. So, it blocked off some signals, including SIGUSR1, on entry to the
SIGSEGV handler, queued a SIGUSR1 to itself, and invoked sigreturn. The
SIGUSR1 was delivered, and was visible to the UML kernel after sigreturn
finished.
The commit eliminated the signal masking and the call to sigreturn. The
handler simply hits itself with a SIGTRAP to let the UML kernel know that it
is finished. UML then restores the process registers, which effectively
longjmps the process out of the signal handler, skipping sigreturn's restoring
of register state and the signal mask.
The bug is that the host apparently sets used_fp to 0 when it saves the
process FP state in the sigcontext on the process signal stack. Thus, when
the process is longjmped out of the handler, its FP state is corrupt because
it wasn't saved on the context switch to the UML kernel.
This manifested itself as sleep hanging. For some reason, sleep uses floating
point in order to calculate the sleep interval. When a page fault corrupts
its FP state, it is faked into essentially sleeping forever.
This patch saves the FP state before entering the SIGSEGV handler and restores
it afterwards.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
[ Spotted by Miklos ]
Fix a memory leak in init_new_context. The struct page ** buffer allocated
for install_special_mapping was never recorded, and thus leaked when the
mm_struct was freed. Fix it by saving the pointer in mm_context_t and freeing
it in arch_exit_mmap.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Style changes under arch/um/os-Linux:
include trimming
CodingStyle fixes
some printks needed severity indicators
make_tempfile turns out not to be used outside of mem.c, so it is now static.
Its declaration in tempfile.h is no longer needed, and tempfile.h itself is no
longer needed.
create_tmp_file was also made static.
checkpatch moans about an EXPORT_SYMBOL in user_syms.c which is part of a
macro definition - this is copying a bit of kernel infrastructure into the
libc side of UML because the kernel headers can't be included there.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Calculate TASK_SIZE at run-time by figuring out the host's VMSPLIT - this is
needed on i386 if UML is to run on hosts with varying VMSPLITs without
recompilation.
TASK_SIZE is now defined in terms of a variable, task_size. This gets rid of
an include of pgtable.h from processor.h, which can cause include loops.
On i386, task_size is calculated early in boot by probing the address space in
a binary search to figure out where the boundary between usable and non-usable
memory is. This tries to make sure that a page that is considered to be in
userspace is, or can be made, read-write. I'm concerned about a system-global
VDSO page in kernel memory being hit and considered to be a userspace page.
On x86_64, task_size is just the old value of CONFIG_TOP_ADDR.
A bunch of config variable are gone now. CONFIG_TOP_ADDR is directly replaced
by TASK_SIZE. NEST_LEVEL is gone since the relocation of the stubs makes it
irrelevant. All the HOST_VMSPLIT stuff is gone. All references to these in
arch/um/Makefile are also gone.
I noticed and fixed a missing extern in os.h when adding os_get_task_size.
Note: This has been revised to fix the 32-bit UML on 64-bit host bug that
Miklos ran into.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Redo the calculation of NR_syscalls since that disappeared from i386 and
use a similar mechanism on x86_64.
We now figure out the size of the system call table in arch code and stick
that in syscall_table_size. arch/um/kernel/skas/syscall.c defines
NR_syscalls in terms of that since its the only thing that needs to know
how many system calls there are.
The old mechananism that was used on x86_64 is gone.
arch/um/include/sysdep-i386/syscalls.h got some formatting since I was
looking at it.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: WANG Cong <xiyou.wangcong@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Style fixes in arch/um/sys-x86_64:
updated copyrights
CodingStyle fixes
added severities to printks which needed them
A bunch of functions in sys-*/ptrace_user.c turn out to be unused, so they and
their declarations are gone.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Add some more commentary about various pieces of global data not needing
locking.
Also got rid of unmap_physmem since that is no longer used.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
init_irq_signals doesn't need to be called from the context of a new process.
It initializes handlers, which are useless in process context. With that call
gone, init_irq_signals has only one caller, so it can be inlined into
init_new_thread_signals.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch moves sig_handler_common_skas from
arch/um/os-Linux/skas/trap.c to its only caller in
arch/um/os-Linux/signal.c. trap.c is now empty, so it can be removed.
This is code movement only - the significant cleanup needed here is
done in the next patch.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Style fixes to arch/um/os/helper.c and tidying up the breakpoint fix a
bit.
helper.c gets all the usual style fixes -
updated copyright
all printks get severities
Also -
errval changes to err in helper_child
fixed an obsolete comment
run_helper was killing a child process which is guaranteed to
be dead or dying anyway
Removed the nohang and pname arguments from helper_wait and fixed the
declaration and callers. nohang was used only in the slirp driver and
I don't think it was needed. I think pname was a bit of overkill in
putting out an error message when something goes wrong.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
It turns out that if there's a panic early enough, UML will just sit there in
the LED-blinking loop because the panic notifier hadn't been installed yet.
This patch installs it earlier.
It also fixes the problem which exposed the hang, namely that if you give UML
a zero-sized initrd, it will ask alloc_bootmem for zero bytes, and that will
cause the panic.
While I was in initrd.c, I gave it a style makeover.
Prompted by checkpatch, I moved a couple extern declarations of uml_exitcode
to kern_util.h.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
setjmp_wrapper existed to provide setjmp to kernel code when UML used libc's
setjmp and longjmp. Now that UML has its own implementation, this isn't
needed and kernel code can invoke setjmp directly.
do_buffer_op is massively cleaned up since it is no longer a callback from
setjmp_wrapper and given a va_list from which it must extract its arguments.
The actual setjmp is moved from buffer_op to do_op_one_page because the copy
operation is inside an atomic section (kmap_atomic to kunmap_atomic) and it
shouldn't be longjmp-ed out of.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
arch/um/os-Linux/file.c needed some style work -
updated the copyright
cleaned up the includes
CodingStyle fixes
added some missing CATCH_EINTRs
os_set_owner was unused, so it is gone
all printks now have severities
fcntl(F_GETFL) was being called without checking the return
removed an obsolete comment
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Code tidying -
the pid field of struct irq_fd isn't used, so it is removed
os_set_fd_async needed to read flags before changing them, it
doesn't need a pid passed in because it can call getpid itself, and a
block of unused code needed deleting
os_get_exec_close was unused, so it is removed
ptrace_child called _exit for historical reasons which are no
longer valid, so just calls exit instead
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Give the stubs a VMA. This allows the removal of a truly nasty kludge to make
sure that mm->nr_ptes was correct in exit_mmap. The underlying problem was
always that the stubs, which have ptes, and thus allocated a page table,
weren't covered by a VMA.
This patch fixes that by using install_special_mapping in arch_dup_mmap and
activate_context to create the VMA. The stubs have to be moved, since
shift_arg_pages seems to assume that the stack is the only VMA present at that
point during exec, and uses vma_adjust to fiddle its VMA. However, that
extends the stub VMA by the amount removed from the stack VMA.
To avoid this problem, the stubs were moved to a different fixed location at
the start of the address space.
The init_stub_pte calls were moved from init_new_context to arch_dup_mmap
because I was occasionally seeing arch_dup_mmap not being called, causing
exit_mmap to die. Rather than figure out what was really happening, I decided
it was cleaner to just move the calls so that there's no doubt that both the
pte and VMA creation happen, no matter what. arch_exit_mmap is used to clear
the stub ptes at exit time.
The STUB_* constants in as-layout.h no longer depend on UM_TASK_SIZE, that
that definition is removed, along with the comments complaining about gcc.
Because the stubs are no longer at the top of the address space, some care is
needed while flushing TLBs. update_pte_range checks for addresses in the stub
range and skips them. flush_thread now issues two unmaps, one for the range
before STUB_START and one for the range after STUB_END.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Clean up the calculation and use of the usable address space size on the host.
task_size is gone, replaced with TASK_SIZE, which is calculated from
CONFIG_TOP_ADDR. get_kmem_end and set_task_sizes_skas are also gone.
host_task_size, which refers to the entire address space usable by the UML
kernel and which may be larger than the address space usable by a UML process,
since that has to end on a pgdir boundary, is replaced by CONFIG_TOP_ADDR.
STACK_TOP is now TASK_SIZE minus the two stub pages.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
UML was panicing in the case of failures of libc calls which shouldn't happen.
This is an overreaction since a failure from libc doesn't normally mean that
kernel data structures are in an unknown state. Instead, the current process
should just be killed if there is no way to recover.
The case that prompted this was a failure of PTRACE_SETREGS restoring the same
state that was read by PTRACE_GETREGS. It appears that when a process tries
to load a bogus value into a segment register, it segfaults (as expected) and
the value is actually loaded and is seen by PTRACE_GETREGS (not expected).
This case is fixed by forcing a fatal SIGSEGV on the process so that it
immediately dies. fatal_sigsegv was added for this purpose. It was declared
as noreturn, so in order to pursuade gcc that it actually does not return, I
added a call to os_dump_core (and declared it noreturn) so that I get a core
file if somehow the process survives.
All other calls in arch/um/os-Linux/skas/process.c got the same treatment,
with failures causing the process to die instead of a kernel panic, with some
exceptions.
userspace_tramp exits with status 1 if anything goes wrong there. That will
cause start_userspace to return an error. copy_context_skas0 and
map_stub_pages also now return errors instead of panicing. Callers of thes
functions were changed to check for errors and do something appropriate.
Usually that's to return an error to their callers.
check_skas3_ptrace_faultinfo just exits since that's too early to do anything
else.
save_registers, restore_registers, and init_registers now return status
instead of panicing on failure, with their callers doing something
appropriate.
There were also duplicate declarations of save_registers and restore_registers
in os.h - these are gone.
I noticed and fixed up some whitespace damage.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Some register accessor cleanups -
userspace() was calling restore_registers and save_registers for no
reason, since userspace() is on the libc side of the house, and these
add no value over calling ptrace directly
init_thread_registers and get_safe_registers were the same thing,
so init_thread_registers is gone
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Untangle UML headers somewhat and add some includes where they were
needed explicitly, but gotten accidentally via some other header.
arch/um/include/um_uaccess.h loses asm/fixmap.h because it uses no
fixmap stuff and gains elf.h, because it needs FIXADDR_USER_*, and
archsetjmp.h, because it needs jmp_buf.
pmd_alloc_one is uninlined because it needs mm_struct, and that's
inconvenient to provide in asm-um/pgtable-3level.h.
elf_core_copy_fpregs is also uninlined from elf-i386.h and
elf-x86_64.h, which duplicated the code anyway, to
arch/um/kernel/process.c, so that the reference to current_thread
doesn't pull sched.h or anything related into asm/elf.h.
arch/um/sys-i386/ldt.c, arch/um/kernel/tlb.c and
arch/um/kernel/skas/uaccess.c got sched.h because they dereference
task_structs. Its includes of linux and asm headers got turned from
"" to <>.
arch/um/sys-i386/bug.c gets asm/errno.h because it needs errno
constants.
asm/elf-i386 gets asm/user.h because it needs user_regs_struct.
asm/fixmap.h gets page.h because it needs PAGE_SIZE and PAGE_MASK and
system.h for BUG_ON.
asm/pgtable doesn't need sched.h.
asm/processor-generic.h defined mm_segment_t, but didn't use it. So,
that definition is moved to uaccess.h, which defines a bunch of
mm_segment_t-related stuff. thread_info.h uses mm_segment_t, and
includes uaccess.h, which causes a recursion. So, the definition is
placed above the include of thread_info. in uaccess.h. thread_info.h
also gets page.h because it needs PAGE_SIZE.
ObCheckpatchViolationJustification - I'm not adding a typedef; I'm
moving mm_segment_t from one place to another.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This patch changes a few functions into returning void. The return values
were not used anyway, so I think it should not be a problem. Also removed a
little leftover bit from TT mode.
Signed-off-by: Karol Swietlicki <magotari@gmail.com>
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Tidy kern_util.h. It turns out that most of the function declarations
aren't used, so they can go away. os.h no longer includes
kern_util.h, so files which got it through os.h now need to include it
directly. A number of other files never needed it, so these includes
are deleted.
The structure which was used to pass signal handlers from the kernel
side to the userspace side is gone. Instead, the handlers are
declared here, and used directly from libc code. This allows
arch/um/os-Linux/trap.c to be deleted, with its remnants being moved
to arch/um/os-Linux/skas/trap.c.
arch/um/os-Linux/tty.c had its inclusions changed, and it needed some
style attention, so it got tidied.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Suggested by Geert Uytterhoeven - use const.h to get constants that are usable
in both C and assembly. I can't include it directly since this code can't
include kernel headers. const.h is also for numeric constants that can be
typed by tacking a "UL" or similar on the end. The constants here have to be
typed by casting them.
So, the relevant parts of const.h are copied here and modified in order to
allow the constants to be uncasted in assembly and casted in C.
Signed-off-by: Jeff Dike <jdike@linux.intel.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
