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  1. 06 4月, 2015 3 次提交
    • B
      x86/alternatives: Guard NOPs optimization · 69df353f
      由 Borislav Petkov 提交于 
      Take a look at the first instruction byte before optimizing the NOP -
there might be something else there already, like the ALTERNATIVE_2()
in rdtsc_barrier() which NOPs out on AMD even though we just
patched in an MFENCE.

This happens because the alternatives sees X86_FEATURE_MFENCE_RDTSC,
AMD CPUs set it, we patch in the MFENCE and right afterwards it sees
X86_FEATURE_LFENCE_RDTSC which AMD CPUs don't set and we blindly
optimize the NOP.

Checking whether at least the first byte is 0x90 prevents that.
Signed-off-by: NBorislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1428181662-18020-1-git-send-email-bp@alien8.deSigned-off-by: NIngo Molnar <mingo@kernel.org>
      69df353f
    • D
      x86/asm/entry: Clear EXTRA_REGS for all executable formats · fc3e958a
      由 Denys Vlasenko 提交于 
      On failure, sys_execve() does not clobber EXTRA_REGS, so we can
just return to userpsace without saving/restoring them.

On success, ELF_PLAT_INIT() in sys_execve() clears all these
registers.

On other executable formats:

  - binfmt_flat.c has similar FLAT_PLAT_INIT, but x86 (and everyone
    else except sh) doesn't define it.

  - binfmt_elf_fdpic.c has ELF_FDPIC_PLAT_INIT, but x86 (and most
    others) doesn't define it.

  - There are no such hooks in binfmt_aout.c et al. We inherit
    EXTRA_REGS from the prior executable.

This inconsistency was not intended.

This change removes SAVE/RESTORE_EXTRA_REGS in stub_execve,
removes register clearing in ELF_PLAT_INIT(),
and instead simply clears them on success in stub_execve.

Run-tested.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1428173719-7637-1-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      fc3e958a
    • B
      x86/signal: Remove pax argument from restore_sigcontext · 6a3713f0
      由 Brian Gerst 提交于 
      The 'pax' argument is unnecesary.  Instead, store the RAX value
directly in regs.

This pattern goes all the way back to 2.1.106pre1, when restore_sigcontext()
was changed to return an error code instead of EAX directly:

  https://git.kernel.org/cgit/linux/kernel/git/history/history.git/diff/arch/i386/kernel/signal.c?id=9a8f8b7ca3f319bd668298d447bdf32730e51174

In 2007 sigaltstack syscall support was added, where the return
value of restore_sigcontext() was changed to carry the memory-copying
failure code.

But instead of putting 'ax' into regs->ax directly, it was carried
in via a pointer and then returned, where the generic syscall return
code copied it to regs->ax.

So there was never any deeper reason for this suboptimal pattern, it
was simply never noticed after being introduced.
Signed-off-by: NBrian Gerst <brgerst@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1428152303-17154-1-git-send-email-brgerst@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      6a3713f0
  3. 04 4月, 2015 1 次提交
    • B
      x86/alternatives: Fix ALTERNATIVE_2 padding generation properly · dbe4058a
      由 Borislav Petkov 提交于 
      Quentin caught a corner case with the generation of instruction
padding in the ALTERNATIVE_2 macro: if len(orig_insn) <
len(alt1) < len(alt2), then not enough padding gets added and
that is not good(tm) as we could overwrite the beginning of the
next instruction.

Luckily, at the time of this writing, we don't have
ALTERNATIVE_2() invocations which have that problem and even if
we did, a simple fix would be to prepend the instructions with
enough prefixes so that that corner case doesn't happen.

However, best it would be if we fixed it properly. See below for
a simple, abstracted example of what we're doing.

So what we ended up doing is, we compute the

	max(len(alt1), len(alt2)) - len(orig_insn)

and feed that value to the .skip gas directive. The max() cannot
have conditionals due to gas limitations, thus the fancy integer
math.

With this patch, all ALTERNATIVE_2 sites get padded correctly;
generating obscure test cases pass too:

  #define alt_max_short(a, b)    ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))

  #define gen_skip(orig, alt1, alt2, marker)	\
  	.skip -((alt_max_short(alt1, alt2) - (orig)) > 0) * \
  		(alt_max_short(alt1, alt2) - (orig)),marker

  	.pushsection .text, "ax"
  .globl main
  main:
  	gen_skip(1, 2, 4, 0x09)
  	gen_skip(4, 1, 2, 0x10)
  	...
  	.popsection

Thanks to Quentin for catching it and double-checking the fix!
Reported-by: NQuentin Casasnovas <quentin.casasnovas@oracle.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150404133443.GE21152@pd.tnicSigned-off-by: NIngo Molnar <mingo@kernel.org>
      dbe4058a
  5. 03 4月, 2015 8 次提交
  7. 02 4月, 2015 3 次提交
  9. 01 4月, 2015 7 次提交
    • D
      x86/asm/entry/64: Use local label to skip around sycall dispatch · a6de5a21
      由 Denys Vlasenko 提交于 
      Logically, we just want to jump around the following instruction
and its prologue/epilogue:

  call *sys_call_table(,%rax,8)

if the syscall number is too big - we do not specifically target
the "int_ret_from_sys_call" label.

Use a local, numerical label for this jump, for more clarity.

This also makes the code smaller:

 -ffffffff8187756b:      0f 87 0f 00 00 00       ja     ffffffff81877580 <int_ret_from_sys_call>
 +ffffffff8187756b:      77 0f                   ja     ffffffff8187757c <int_ret_from_sys_call>

because jumps to global labels are never translated to short jump
instructions by GAS.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427821211-25099-9-git-send-email-dvlasenk@redhat.com
[ Improved the changelog. ]
Signed-off-by: NIngo Molnar <mingo@kernel.org>
      a6de5a21
    • D
      x86/asm: Replace "MOVQ $imm, %reg" with MOVL · a734b4a2
      由 Denys Vlasenko 提交于 
      There is no reason to use MOVQ to load a non-negative immediate
constant value into a 64-bit register. MOVL does the same, since
the upper 32 bits are zero-extended by the CPU.

This makes the code a bit smaller, while leaving functionality
unchanged.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427821211-25099-8-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      a734b4a2
    • D
      x86/asm/entry/64: Simplify looping around preempt_schedule_irq() · 36acef25
      由 Denys Vlasenko 提交于 
      At the 'exit_intr' label we test whether interrupt/exception was in
kernel. If it did, we jump to the preemption check. If preemption
does happen (IOW if we call preempt_schedule_irq()), we go back to
'exit_intr'.

But it's pointless, we already know that the test succeeded last
time, preemption doesn't change the fact that interrupt/exception
was in the kernel.

We can go back directly to checking PER_CPU_VAR(__preempt_count) instead.

This makes the 'exit_intr' label unused, drop it.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427821211-25099-5-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      36acef25
    • D
      x86/asm/entry/64: Remove redundant DISABLE_INTERRUPTS() · 32a04077
      由 Denys Vlasenko 提交于 
      At this location, we already have interrupts off, always.
To be more specific, we already disabled them here:

    ret_from_intr:
	    DISABLE_INTERRUPTS(CLBR_NONE)
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427821211-25099-4-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      32a04077
    • D
      x86/asm/entry/64: Simplify retint_kernel label usage, make retint_restore_args label local · 6ba71b76
      由 Denys Vlasenko 提交于 
      Get rid of #define obfuscation of retint_kernel in
CONFIG_PREEMPT case by defining retint_kernel label always, not
only for CONFIG_PREEMPT.

Strip retint_kernel of .global-ness (ENTRY macro) - it has no
users outside of this file.

This looks like cosmetics, but it is not:
"je LABEL" can be optimized to short jump by assember
only if LABEL is not global, for global labels jump is always
a near one with relocation.

Convert retint_restore_args to a local numeric label, making it
clearer that it is not used elsewhere in the file.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427821211-25099-3-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      6ba71b76
    • D
      x86/asm/entry/32: Use smaller PUSH instructions instead of MOV, to build 'pt_regs' on stack · 4c9c0e91
      由 Denys Vlasenko 提交于 
      This mimics the recent similar 64-bit change.
Saves ~110 bytes of code.

Patch was run-tested on 32 and 64 bits, Intel and AMD CPU.
I also looked at the diff of entry_64.o disassembly, to have
a different view of the changes.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427821211-25099-2-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      4c9c0e91
    • D
      x86/asm/entry/64: Do not TRACE_IRQS fast SYSRET64 path · 4416c5a6
      由 Denys Vlasenko 提交于 
      SYSRET code path has a small irq-off block.
On this code path, TRACE_IRQS_ON can't be called right before
interrupts are enabled for real, we can't clobber registers
there. So current code does it earlier, in a safe place.

But with this, TRACE_IRQS_OFF/ON frames just two fast
instructions, which is ridiculous: now most of irq-off block is
_outside_ of the framing.

Do the same thing that we do on SYSCALL entry: do not track this
irq-off block, it is very small to ever cause noticeable irq
latency.

Be careful: make sure that "jnz int_ret_from_sys_call_irqs_off"
now does invoke TRACE_IRQS_OFF - move
int_ret_from_sys_call_irqs_off label before TRACE_IRQS_OFF.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427821211-25099-1-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      4416c5a6
  11. 31 3月, 2015 3 次提交
    • I
      x86/asm/entry: Remove user_mode_ignore_vm86() · 55474c48
      由 Ingo Molnar 提交于 
      user_mode_ignore_vm86() can be used instead of user_mode(), in
places where we have already done a v8086_mode() security
check of ptregs.

But doing this check in the wrong place would be a bug that
could result in security problems, and also the naming still
isn't very clear.

Furthermore, it only affects 32-bit kernels, while most
development happens on 64-bit kernels.

If we replace them with user_mode() checks then the cost is only
a very minor increase in various slowpaths:

   text             data   bss     dec              hex    filename
   10573391         703562 1753042 13029995         c6d26b vmlinux.o.before
   10573423         703562 1753042 13030027         c6d28b vmlinux.o.after

So lets get rid of this distinction once and for all.
Acked-by: NBorislav Petkov <bp@suse.de>
Acked-by: NAndy Lutomirski <luto@kernel.org>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brad Spengler <spender@grsecurity.net>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150329090233.GA1963@gmail.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      55474c48
    • D
      x86/asm/entry/64: Do not GET_THREAD_INFO() too early · a3675b32
      由 Denys Vlasenko 提交于 
      At exit_intr, we GET_THREAD_INFO(%rcx) and then jump to
retint_kernel if saved CS was from kernel. But the code at
retint_kernel doesn't need %rcx.

Move GET_THREAD_INFO(%rcx) down, after CS check and branch.

While at it, remove "has a correct top of stack" comment.
After recent changes which eliminated FIXUP_TOP_OF_STACK,
we always have a correct pt_regs layout.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427738975-7391-5-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      a3675b32
    • D
      x86/asm/entry/64: Move retint_kernel code block closer to its user · 627276cb
      由 Denys Vlasenko 提交于 
      The "retint_kernel" code block is misplaced. Since its logical
continuation is "retint_restore_args", it is more natural to
place it above that label. This also makes two jumps "short".

This change only moves code block around, without changing
logic.

This enables the next simplification: making
"retint_restore_args" label a local numeric one.
Signed-off-by: NDenys Vlasenko <dvlasenk@redhat.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Will Drewry <wad@chromium.org>
Link: http://lkml.kernel.org/r/1427738975-7391-2-git-send-email-dvlasenk@redhat.comSigned-off-by: NIngo Molnar <mingo@kernel.org>
      627276cb
  13. 27 3月, 2015 9 次提交
  15. 25 3月, 2015 6 次提交