Commit Graph

14 Commits

Author SHA1 Message Date
Paolo 'Blaisorblade' Giarrusso aa6758d486 [PATCH] uml: implement {get,set}_thread_area for i386
Implement sys_[gs]et_thread_area and the corresponding ptrace operations for
UML.  This is the main chunk, additional parts follow.  This implementation is
now well tested and has run reliably for some time, and we've understood all
the previously existing problems.

Their implementation saves the new GDT content and then forwards the call to
the host when appropriate, i.e.  immediately when the target process is
running or on context switch otherwise (i.e.  on fork and on ptrace() calls).

In SKAS mode, we must switch registers on each context switch (because SKAS
does not switches tls_array together with current->mm).

Also, added get_cpu() locking; this has been done for SKAS mode, since TT does
not need it (it does not use smp_processor_id()).

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Acked-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-31 12:18:52 -08:00
Al Viro 7b99edc78d [PATCH] uml: clean up remapping code build magic
kills unmap magic

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-31 12:18:51 -08:00
Al Viro de2fe5e07d [PATCH] uml: eliminate symlinks to host arch
kills symlinks in arch/um/sys-*

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-31 12:18:50 -08:00
Paolo 'Blaisorblade' Giarrusso 63b4444241 [PATCH] uml: fix compilation with CONFIG_MODE_TT disabled
Fix UML compilation when SKAS mode is disabled. Indeed, we were compiling
SKAS-only object files, which failed due to some SKAS-only headers being
excluded from the search path.

Thanks to the bug report from Pekka J Enberg.

Acked-by: Pekka J Enberg <penberg (at) cs ! helsinki ! fi>
Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-12-29 09:48:15 -08:00
Jeff Dike 17d469715c [PATCH] uml: properly invoke x86_64 system calls
This patch makes stub_segv use the stub_syscall macros.  This was needed
anyway, but the bug that prompted this was the discovery that gcc was storing
stuff in RCX, which is trashed across a system call.  This is exactly the sort
of problem that the new macros fix.

There is a stub_syscall0 for getpid.  stub_segv was changed to be a libc file,
and that caused some include changes.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-11-22 09:13:41 -08:00
Al Viro ecba97d4aa [PATCH] uml makefiles sanitized
UML makefiles sanitized:
 - number of generated headers reduced to 2 (from user-offsets.c and
   kernel-offsets.c resp.).  The rest is made constant and simply
   includes those two.
 - mk_... helpers are gone now that we don't need to generate these
   headers
 - arch/um/include2 removed since everything under arch/um/include/sysdep
   is constant now and symlink can point straight to source tree.
 - dependencies seriously simplified.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-29 08:46:26 -07:00
Al Viro 30f7dabb08 [PATCH] uml: build cleanups
Added missing include list to uml AFLAGS

Killed magic for stubs.  [So] - it was needed only because of messed AFLAGS
Switched segv_stubs.c to kernel CFLAGS sans profile, instead of user ones
Killed STUBS_CFLAGS - it's not needed and the only remaining use had been
gratitious - it only polluted CFLAGS

Signed-off-by: Al Viro <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-05 00:06:23 -07:00
Al Viro 93ea5a5b5c [PATCH] uml: build cleanup
Build cleanups

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: Paolo Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-09-05 00:06:22 -07:00
Jeff Dike d67b569f5f [PATCH] uml: skas0 - separate kernel address space on stock hosts
UML has had two modes of operation - an insecure, slow mode (tt mode) in
which the kernel is mapped into every process address space which requires
no host kernel modifications, and a secure, faster mode (skas mode) in
which the UML kernel is in a separate host address space, which requires a
patch to the host kernel.

This patch implements something very close to skas mode for hosts which
don't support skas - I'm calling this skas0.  It provides the security of
the skas host patch, and some of the performance gains.

The two main things that are provided by the skas patch, /proc/mm and
PTRACE_FAULTINFO, are implemented in a way that require no host patch.

For the remote address space changing stuff (mmap, munmap, and mprotect),
we set aside two pages in the process above its stack, one of which
contains a little bit of code which can call mmap et al.

To update the address space, the system call information (system call
number and arguments) are written to the stub page above the code.  The
%esp is set to the beginning of the data, the %eip is set the the start of
the stub, and it repeatedly pops the information into its registers and
makes the system call until it sees a system call number of zero.  This is
to amortize the cost of the context switch across multiple address space
updates.

When the updates are done, it SIGSTOPs itself, and the kernel process
continues what it was doing.

For a PTRACE_FAULTINFO replacement, we set up a SIGSEGV handler in the
child, and let it handle segfaults rather than nullifying them.  The
handler is in the same page as the mmap stub.  The second page is used as
the stack.  The handler reads cr2 and err from the sigcontext, sticks them
at the base of the stack in a faultinfo struct, and SIGSTOPs itself.  The
kernel then reads the faultinfo and handles the fault.

A complication on x86_64 is that this involves resetting the registers to
the segfault values when the process is inside the kill system call.  This
breaks on x86_64 because %rcx will contain %rip because you tell SYSRET
where to return to by putting the value in %rcx.  So, this corrupts $rcx on
return from the segfault.  To work around this, I added an
arch_finish_segv, which on x86 does nothing, but which on x86_64 ptraces
the child back through the sigreturn.  This causes %rcx to be restored by
sigreturn and avoids the corruption.  Ultimately, I think I will replace
this with the trick of having it send itself a blocked signal which will be
unblocked by the sigreturn.  This will allow it to be stopped just after
the sigreturn, and PTRACE_SYSCALLed without all the back-and-forth of
PTRACE_SYSCALLing it through sigreturn.

This runs on a stock host, so theoretically (and hopefully), tt mode isn't
needed any more.  We need to make sure that this is better in every way
than tt mode, though.  I'm concerned about the speed of address space
updates and page fault handling, since they involve extra round-trips to
the child.  We can amortize the round-trip cost for large address space
updates by writing all of the operations to the data page and having the
child execute them all at the same time.  This will help fork and exec, but
not page faults, since they involve only one page.

I can't think of any way to help page faults, except to add something like
PTRACE_FAULTINFO to the host.  There is PTRACE_SIGINFO, but UML doesn't use
siginfo for SIGSEGV (or anything else) because there isn't enough
information in the siginfo struct to handle page faults (the faulting
operation type is missing).  Adding that would make PTRACE_SIGINFO a usable
equivalent to PTRACE_FAULTINFO.

As for the code itself:

- The system call stub is in arch/um/kernel/sys-$(SUBARCH)/stub.S.  It is
  put in its own section of the binary along with stub_segv_handler in
  arch/um/kernel/skas/process.c.  This is manipulated with run_syscall_stub
  in arch/um/kernel/skas/mem_user.c.  syscall_stub will execute any system
  call at all, but it's only used for mmap, munmap, and mprotect.

- The x86_64 stub calls sigreturn by hand rather than allowing the normal
  sigreturn to happen, because the normal sigreturn is a SA_RESTORER in
  UML's address space provided by libc.  Needless to say, this is not
  available in the child's address space.  Also, it does a couple of odd
  pops before that which restore the stack to the state it was in at the
  time the signal handler was called.

- There is a new field in the arch mmu_context, which is now a union.
  This is the pid to be manipulated rather than the /proc/mm file
  descriptor.  Code which deals with this now checks proc_mm to see whether
  it should use the usual skas code or the new code.

- userspace_tramp is now used to create a new host process for every UML
  process, rather than one per UML processor.  It checks proc_mm and
  ptrace_faultinfo to decide whether to map in the pages above its stack.

- start_userspace now makes CLONE_VM conditional on proc_mm since we need
  separate address spaces now.

- switch_mm_skas now just sets userspace_pid[0] to the new pid rather
  than PTRACE_SWITCH_MM.  There is an addition to userspace which updates
  its idea of the pid being manipulated each time around the loop.  This is
  important on exec, when the pid will change underneath userspace().

- The stub page has a pte, but it can't be mapped in using tlb_flush
  because it is part of tlb_flush.  This is why it's required for it to be
  mapped in by userspace_tramp.

Other random things:

- The stub section in uml.lds.S is page aligned.  This page is written
  out to the backing vm file in setup_physmem because it is mapped from
  there into user processes.

- There's some confusion with TASK_SIZE now that there are a couple of
  extra pages that the process can't use.  TASK_SIZE is considered by the
  elf code to be the usable process memory, which is reasonable, so it is
  decreased by two pages.  This confuses the definition of
  USER_PGDS_IN_LAST_PML4, making it too small because of the rounding down
  of the uneven division.  So we round it to the nearest PGDIR_SIZE rather
  than the lower one.

- I added a missing PT_SYSCALL_ARG6_OFFSET macro.

- um_mmu.h was made into a userspace-usable file.

- proc_mm and ptrace_faultinfo are globals which say whether the host
  supports these features.

- There is a bad interaction between the mm.nr_ptes check at the end of
  exit_mmap, stack randomization, and skas0.  exit_mmap will stop freeing
  pages at the PGDIR_SIZE boundary after the last vma.  If the stack isn't
  on the last page table page, the last pte page won't be freed, as it
  should be since the stub ptes are there, and exit_mmap will BUG because
  there is an unfreed page.  To get around this, TASK_SIZE is set to the
  next lowest PGDIR_SIZE boundary and mm->nr_ptes is decremented after the
  calls to init_stub_pte.  This ensures that we know the process stack (and
  all other process mappings) will be below the top page table page, and
  thus we know that mm->nr_ptes will be one too many, and can be
  decremented.

Things that need fixing:

- We may need better assurrences that the stub code is PIC.

- The stub pte is set up in init_new_context_skas.

- alloc_pgdir is probably the right place.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-07-07 18:23:44 -07:00
Paolo 'Blaisorblade' Giarrusso 60b2737de1 [PATCH] uml: fix linkage of tt mode against NPTL
With Al Viro <viro@parcelfarce.linux.theplanet.co.uk>

To make sure switcheroo() can execute when we remap all the executable
image, we used a trick to make it use a local copy of errno...  this trick
does not work with NPTL glibc, only with LinuxThreads, so use another
(simpler) one to make it work anyway.

Hopefully, a lot improved thanks to merging with the version of Al Viro
(which had his part of problems, though, i.e.  removing a fix to another
bug and not fixing the problem on i386).

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-06-21 19:07:32 -07:00
Jeff Dike ba9950c820 [PATCH] uml: small fixes left over from rc4
Some changes that I sent in didn't make 2.6.12-rc4 for some reason.  This
adds them back.  We have
	an x86_64 definition of TOP_ADDR
	a reimplementation of the x86_64 csum_partial_copy_from_user
	some syntax fixes in arch/um/kernel/ptrace.c
	removal of a CFLAGS definition in the x86_64 Makefile
	some include changes in the x86_64 ptrace.c and user-offsets.h
	a syntax fix in elf-x86_64.h
Also moved an include in the i386 and x86_64 Makefiles to make the symlinks
work, and some small fixes from Al Viro.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Cc: <viro@parcelfarce.linux.theplanet.co.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-20 15:48:17 -07:00
Paolo 'Blaisorblade' Giarrusso 776cfebb43 [PATCH] uml kbuild: avoid useless rebuilds
- Fix some problems with usage of $(targets) (sometimes missing, sometimes
  used badly) that trigger partial rebuilds when doing a rebuild.

- At that purpose, also factor out some common code for symlinks creation.

- Fix a x86-64 build warning, caused by -L/usr/lib, which is anyway useless,
  and invalid in the x86-64 case.

Tested on x86_64 and x86.

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-05 16:36:33 -07:00
Paolo 'Blaisorblade' Giarrusso 5e7b83ffc6 [PATCH] uml: fix syscall table by including $(SUBARCH)'s one, for i386
Split the i386 entry.S files into entry.S and syscall_table.S which is
included in the previous one (so actually there is no difference between them)
and use the syscall_table.S in the UML build, instead of tracking by hand the
syscall table changes (which is inherently error-prone).

We must only insert the right #defines to inject the changes we need from the
i386 syscall table (for instance some different function names); also, we
don't implement some i386 syscalls, as ioperm(), nor some TLS-related ones
(yet to provide).

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-01 08:58:55 -07:00
Linus Torvalds 1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00