linux.git/arch/powerpc/kernel/exceptions-64s.S, branch v3.18.64

powerpc/book3s64: Fix branching to OOL handlers in relocatable kernel

2016-06-03T15:30:27+00:00

[ Upstream commit 8ed8ab40047a570fdd8043a40c104a57248dd3fd ]

Some of the interrupt vectors on 64-bit POWER server processors are only
32 bytes long (8 instructions), which is not enough for the full
first-level interrupt handler. For these we need to branch to an
out-of-line (OOL) handler. But when we are running a relocatable kernel,
interrupt vectors till __end_interrupts marker are copied down to real
address 0x100. So, branching to labels (ie. OOL handlers) outside this
section must be handled differently (see LOAD_HANDLER()), considering
relocatable kernel, which would need at least 4 instructions.

However, branching from interrupt vector means that we corrupt the
CFAR (come-from address register) on POWER7 and later processors as
mentioned in commit 1707dd16. So, EXCEPTION_PROLOG_0 (6 instructions)
that contains the part up to the point where the CFAR is saved in the
PACA should be part of the short interrupt vectors before we branch out
to OOL handlers.

But as mentioned already, there are interrupt vectors on 64-bit POWER
server processors that are only 32 bytes long (like vectors 0x4f00,
0x4f20, etc.), which cannot accomodate the above two cases at the same
time owing to space constraint. Currently, in these interrupt vectors,
we simply branch out to OOL handlers, without using LOAD_HANDLER(),
which leaves us vulnerable when running a relocatable kernel (eg. kdump
case). While this has been the case for sometime now and kdump is used
widely, we were fortunate not to see any problems so far, for three
reasons:

  1. In almost all cases, production kernel (relocatable) is used for
     kdump as well, which would mean that crashed kernel's OOL handler
     would be at the same place where we end up branching to, from short
     interrupt vector of kdump kernel.
  2. Also, OOL handler was unlikely the reason for crash in almost all
     the kdump scenarios, which meant we had a sane OOL handler from
     crashed kernel that we branched to.
  3. On most 64-bit POWER server processors, page size is large enough
     that marking interrupt vector code as executable (see commit
     429d2e83) leads to marking OOL handler code from crashed kernel,
     that sits right below interrupt vector code from kdump kernel, as
     executable as well.

Let us fix this by moving the __end_interrupts marker down past OOL
handlers to make sure that we also copy OOL handlers to real address
0x100 when running a relocatable kernel.

This fix has been tested successfully in kdump scenario, on an LPAR with
4K page size by using different default/production kernel and kdump
kernel.

Also tested by manually corrupting the OOL handlers in the first kernel
and then kdump'ing, and then causing the OOL handlers to fire - mpe.

Fixes: c1fb6816fb1b ("powerpc: Add relocation on exception vector handlers")
Cc: stable@vger.kernel.org
Signed-off-by: Hari Bathini 
Signed-off-by: Mahesh Salgaonkar 
Signed-off-by: Michael Ellerman 
Signed-off-by: Sasha Levin

powerpc/book3s: Fix the MCE code to use CONFIG_KVM_BOOK3S_64_HANDLER

2015-04-17T00:13:16+00:00

[ Upstream commit 44d5f6f5901e996744858c175baee320ccf1eda3 ]

commit id 2ba9f0d has changed CONFIG_KVM_BOOK3S_64_HV to tristate to allow
HV/PR bits to be built as modules. But the MCE code still depends on
CONFIG_KVM_BOOK3S_64_HV which is wrong. When user selects
CONFIG_KVM_BOOK3S_64_HV=m to build HV/PR bits as a separate module the
relevant MCE code gets excluded.

This patch fixes the MCE code to use CONFIG_KVM_BOOK3S_64_HANDLER. This
makes sure that the relevant MCE code is included when HV/PR bits
are built as a separate modules.

Fixes: 2ba9f0d88750 ("kvm: powerpc: book3s: Support building HV and PR KVM as module")
Cc: stable@vger.kernel.org  # v3.14+
Signed-off-by: Mahesh Salgaonkar 
Acked-by: Paul Mackerras 
Signed-off-by: Michael Ellerman 
Signed-off-by: Sasha Levin

powerpc/book3s: Don't clear MSR_RI in hmi handler.

2014-10-10T06:25:25+00:00

In HMI interrupt handler we don't touch SRR0/SRR1, instead we touch
HSRR0/HSRR1. Hence we don't need to clear MSR_RI bit.

Signed-off-by: Mahesh Salgaonkar 
Signed-off-by: Michael Ellerman

powerpc: Fix "attempt to move .org backwards" error

2014-08-13T05:13:25+00:00

Once again, we see

arch/powerpc/kernel/exceptions-64s.S: Assembler messages:
arch/powerpc/kernel/exceptions-64s.S:865: Error: attempt to move .org backwards
arch/powerpc/kernel/exceptions-64s.S:866: Error: attempt to move .org backwards
arch/powerpc/kernel/exceptions-64s.S:890: Error: attempt to move .org backwards

when compiling ppc:allmodconfig.

This time the problem has been caused by to commit 0869b6fd209bda
("powerpc/book3s: Add basic infrastructure to handle HMI in Linux"),
which adds functions hmi_exception_early and hmi_exception_after_realmode
into a critical (size-limited) code area, even though that does not appear
to be necessary.

Move those functions to a non-critical area of the file.

Signed-off-by: Guenter Roeck 
Signed-off-by: Benjamin Herrenschmidt

powerpc/book3s: Add basic infrastructure to handle HMI in Linux.

2014-08-05T06:33:48+00:00

Handle Hypervisor Maintenance Interrupt (HMI) in Linux. This patch implements
basic infrastructure to handle HMI in Linux host. The design is to invoke
opal handle hmi in real mode for recovery and set irq_pending when we hit HMI.
During check_irq_replay pull opal hmi event and print hmi info on console.

Signed-off-by: Mahesh Salgaonkar 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Remove misleading DISABLE_INTS

2014-07-28T04:11:24+00:00

DISABLE_INTS has a long and storied history, but for some time now it
has not actually disabled interrupts.

For the open-coded exception handlers, just stop using it, instead call
RECONCILE_IRQ_STATE directly. This has the benefit of removing a level
of indirection, and making it clear that r10 & r11 are used at that
point.

For the addition case we still need a macro, so rename it to clarify
what it actually does.

Signed-off-by: Michael Ellerman 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Move bad_stack() below the fwnmi_data_area

2014-07-28T04:11:22+00:00

At the moment the allmodconfig build is failing because we run out of
space between altivec_assist() at 0x5700 and the fwnmi_data_area at
0x7000.

Fixing it permanently will take some more work, but a quick fix is to
move bad_stack() below the fwnmi_data_area. That gives us just enough
room with everything enabled.

bad_stack() is called from the common exception handlers, but it's a
non-conditional branch, so we have plenty of scope to move it further
way.

Signed-off-by: Michael Ellerman 
Signed-off-by: Benjamin Herrenschmidt

powerpc: Remove STAB code

2014-07-28T04:10:22+00:00

Old cpus didn't have a Segment Lookaside Buffer (SLB), instead they had
a Segment Table (STAB). Now that we've dropped support for those cpus,
we can remove the STAB support entirely.

Signed-off-by: Michael Ellerman 
Signed-off-by: Benjamin Herrenschmidt

powerpc/book3s: Fix some ABIv2 issues in machine check code

2014-06-11T23:41:33+00:00

Commit 2749a2f26a7c (powerpc/book3s: Fix machine check handling for
unhandled errors) introduced a few ABIv2 issues.

We can maintain ABIv1 and ABIv2 compatibility by branching to the
function rather than the dot symbol.

Fixes: 2749a2f26a7c ("powerpc/book3s: Fix machine check handling for unhandled errors")
Signed-off-by: Anton Blanchard 
Signed-off-by: Benjamin Herrenschmidt

powerpc/book3s: Add stack overflow check in machine check handler.

2014-06-11T09:15:13+00:00

Currently machine check handler does not check for stack overflow for
nested machine check. If we hit another MCE while inside the machine check
handler repeatedly from same address then we get into risk of stack
overflow which can cause huge memory corruption. This patch limits the
nested MCE level to 4 and panic when we cross level 4.

Signed-off-by: Mahesh Salgaonkar 
Signed-off-by: Benjamin Herrenschmidt