On the 80486 DX, it seems that some exceptions may leave garbage in
the high bits of CS. This causes sporadic failures in which
early_fixup_exception() refuses to fix up an exception.
As far as I can tell, this has been buggy for a long time, but the
problem seems to have been exacerbated by commits:
1e02ce4ccc ("x86: Store a per-cpu shadow copy of CR4")
e1bfc11c5a ("x86/init: Fix cr4_init_shadow() on CR4-less machines")
This appears to have broken for as long as we've had early
exception handling.
[ Note to stable maintainers: This patch is needed all the way back to 3.4,
but it will only apply to 4.6 and up, as it depends on commit:
0e861fbb5b ("x86/head: Move early exception panic code into early_fixup_exception()")
If you want to backport to kernels before 4.6, please don't backport the
prerequisites (there was a big chain of them that rewrote a lot of the
early exception machinery); instead, ask me and I can send you a one-liner
that will apply. ]
Reported-by: Matthew Whitehead <tedheadster@gmail.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
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: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Fixes: 4c5023a3fa ("x86-32: Handle exception table entries during early boot")
Link: http://lkml.kernel.org/r/cb32c69920e58a1a58e7b5cad975038a69c0ce7d.1479609510.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
These files were only including module.h for exception table related
functions. We've now separated that content out into its own file
"extable.h" so now move over to that and avoid all the extra header content
in module.h that we don't really need to compile these files.
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Link: http://lkml.kernel.org/r/20160919210418.30243-1-paul.gortmaker@windriver.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Pull x86 stackdump update from Ingo Molnar:
"A number of stackdump enhancements"
* 'x86-debug-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
x86/dumpstack: Add show_stack_regs() and use it
printk: Make the printk*once() variants return a value
x86/dumpstack: Honor supplied @regs arg
struct thread_info is a legacy mess. To prepare for its partial removal,
move the uaccess control fields out -- they're straightforward.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
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: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/d0ac4d01c8e4d4d756264604e47445d5acc7900e.1468527351.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Add a helper to dump supplied pt_regs and use it in the MSR exception
handling code to have precise stack traces pointing to the actual
function causing the MSR access exception and not the stack frame of the
exception handler itself.
The new output looks like this:
unchecked MSR access error: RDMSR from 0xdeadbeef at rIP: 0xffffffff8102ddb6 (early_init_intel+0x16/0x3a0)
00000000756e6547 ffffffff81c03f68 ffffffff81dd0940 ffffffff81c03f10
ffffffff81d42e65 0000000001000000 ffffffff81c03f58 ffffffff81d3e5a3
0000800000000000 ffffffff81800080 ffffffffffffffff 0000000000000000
Call Trace:
[<ffffffff81d42e65>] early_cpu_init+0xe7/0x136
[<ffffffff81d3e5a3>] setup_arch+0xa5/0x9df
[<ffffffff81d38bb9>] start_kernel+0x9f/0x43a
[<ffffffff81d38294>] x86_64_start_reservations+0x2f/0x31
[<ffffffff81d383fe>] x86_64_start_kernel+0x168/0x176
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
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: Frederic Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1467671487-10344-4-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
On AMD CPUs, a failed loadsegment currently may not clear the FS
base. Fix it.
While we're at it, prevent loadsegment(gs, xyz) from even compiling
on 64-bit kernels. It shouldn't be used.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
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: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/a084c1b93b7b1408b58d3fd0b5d6e47da8e7d7cf.1461698311.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Borislav asked for a comment explaining why all exception handlers are
allowed early.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Reviewed-by: Borislav Petkov <bp@suse.de>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/5f1dcd6919f4a5923959a8065cb2c04d9dac1412.1459784772.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This demotes an OOPS and likely panic due to a failed non-"safe" MSR
access to a WARN_ONCE() and, for RDMSR, a return value of zero.
To be clear, this type of failure should *not* happen. This patch
exists to minimize the chance of nasty undebuggable failures
happening when a CONFIG_PARAVIRT=y bug in the non-"safe" MSR helpers
gets fixed.
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/26567b216aae70e795938f4b567eace5a0eb90ba.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Now that early_fixup_exception() has pt_regs, we can just call
fixup_exception() from it. This will make fancy exception handlers
work early.
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/20fc047d926150cb08cb9b9f2923519b07ec1a15.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This removes a bunch of assembly and adds some C code instead. It
changes the actual printouts on both 32-bit and 64-bit kernels, but
they still seem okay.
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/4085070316fc3ab29538d3fcfe282648d1d4ee2e.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
C is nicer than asm.
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/dd068269f8d59fe44e9e43a50d0efd67da65c2b5.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
early_fixup_exception() is limited by the fact that it doesn't have a
real struct pt_regs. Change both the 32-bit and 64-bit asm and the
C code to pass and accept a real pt_regs.
Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/e3fb680fcfd5e23e38237e8328b64a25cc121d37.1459605520.git.luto@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Replace the arch specific versions of search_extable() and
sort_extable() with calls to the generic ones, which now support
relative exception tables as well.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: H. Peter Anvin <hpa@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Huge amounts of help from Andy Lutomirski and Borislav Petkov to
produce this. Andy provided the inspiration to add classes to the
exception table with a clever bit-squeezing trick, Boris pointed
out how much cleaner it would all be if we just had a new field.
Linus Torvalds blessed the expansion with:
' I'd rather not be clever in order to save just a tiny amount of space
in the exception table, which isn't really criticial for anybody. '
The third field is another relative function pointer, this one to a
handler that executes the actions.
We start out with three handlers:
1: Legacy - just jumps the to fixup IP
2: Fault - provide the trap number in %ax to the fixup code
3: Cleaned up legacy for the uaccess error hack
Signed-off-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Borislav Petkov <bp@suse.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/f6af78fcbd348cf4939875cfda9c19689b5e50b8.1455732970.git.tony.luck@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Switch to using relative exception table entries on x86. On i386,
this has the advantage that the exception table entries don't need to
be relocated; on x86-64 this means the exception table entries take up
only half the space.
In either case, a 32-bit delta is sufficient, as the range of kernel
code addresses is limited.
Since part of the goal is to avoid needing to adjust the entries when
the kernel is relocated, the old trick of using addresses in the NULL
pointer range to indicate uaccess_err no longer works (and unlike RISC
architectures we can't use a flag bit); instead use an delta just
below +2G to indicate these special entries. The reach is still
limited to a single instruction.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Cc: David Daney <david.daney@cavium.com>
Link: http://lkml.kernel.org/r/CA%2B55aFyijf43qSu3N9nWHEBwaGbb7T2Oq9A=9EyR=Jtyqfq_cQ@mail.gmail.com
Add a restricted version of fixup_exception() to be used during early
boot only. In particular, this doesn't support the try..catch variant
since we may not have a thread_info set up yet.
This relies on the exception table being sorted already at build time.
Link: http://lkml.kernel.org/r/1334794610-5546-1-git-send-email-hpa@zytor.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
To make this work, we teach the page fault handler how to send
signals on failed uaccess. This only works for user addresses
(kernel addresses will never hit the page fault handler in the
first place), so we need to generate signals for those
separately.
This gets the tricky case right: if the user buffer spans
multiple pages and only the second page is invalid, we set
cr2 and si_addr correctly. UML relies on this behavior to
"fault in" pages as needed.
We steal a bit from thread_info.uaccess_err to enable this.
Before this change, uaccess_err was a 32-bit boolean value.
This fixes issues with UML when vsyscall=emulate.
Reported-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: richard -rw- weinberger <richard.weinberger@gmail.com>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/4c8f91de7ec5cd2ef0f59521a04e1015f11e42b4.1320712291.git.luto@amacapital.net
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Move the handling of truncated %rip from an iret fault to the fault
entry path.
This allows x86-64 to use the standard search_extable() function.
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Jan Beulich <jbeulich@novell.com>
LKML-Reference: <1255357103-5418-1-git-send-email-brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Impact: introduce new uaccess exception handling framework
Introduce {get|put}_user_try and {get|put}_user_catch as new uaccess exception
handling framework.
{get|put}_user_try begins exception block and {get|put}_user_catch(err) ends
the block and gets err if an exception occured in {get|put}_user_ex() in the
block. The exception is stored thread_info->uaccess_err.
The example usage of this framework is below;
int func()
{
int err = 0;
get_user_try {
get_user_ex(...);
get_user_ex(...);
:
} get_user_catch(err);
return err;
}
Note: get_user_ex() is not clear the value when an exception occurs, it's
different from the behavior of __get_user(), but I think it doesn't matter.
Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Introduce fixup_exception() on 64-bit and use it in kprobes to
eliminate an #ifdef.
Only 64-bit needs search_extable() due to a stepping bug.
Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
