linux-toradex.git/arch/powerpc/kernel/entry_64.S, branch v4.4.129

powerpc/64: Convert the syscall exit path to use RFI_TO_USER/KERNEL

2018-02-16T19:09:35+00:00

commit b8e90cb7bc04a509e821e82ab6ed7a8ef11ba333 upstream.

In the syscall exit path we may be returning to user or kernel
context. We already have a test for that, because we conditionally
restore r13. So use that existing test and branch, and bifurcate the
return based on that.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

powerpc/64: Convert fast_exception_return to use RFI_TO_USER/KERNEL

2018-02-16T19:09:34+00:00

commit a08f828cf47e6c605af21d2cdec68f84e799c318 upstream.

Similar to the syscall return path, in fast_exception_return we may be
returning to user or kernel context. We already have a test for that,
because we conditionally restore r13. So use that existing test and
branch, and bifurcate the return based on that.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

powerpc/64s: Simple RFI macro conversions

2018-02-16T19:09:34+00:00

commit 222f20f140623ef6033491d0103ee0875fe87d35 upstream.

This commit does simple conversions of rfi/rfid to the new macros that
include the expected destination context. By simple we mean cases
where there is a single well known destination context, and it's
simply a matter of substituting the instruction for the appropriate
macro.

Signed-off-by: Nicholas Piggin 
Signed-off-by: Michael Ellerman 
[Balbir fixed issues with backporting to stable]
Signed-off-by: Balbir Singh 
Signed-off-by: Greg Kroah-Hartman

powerpc/kprobe: Fix oops when kprobed on 'stdu' instruction

2017-04-27T07:09:33+00:00

commit 9e1ba4f27f018742a1aa95d11e35106feba08ec1 upstream.

If we set a kprobe on a 'stdu' instruction on powerpc64, we see a kernel
OOPS:

  Bad kernel stack pointer cd93c840 at c000000000009868
  Oops: Bad kernel stack pointer, sig: 6 [#1]
  ...
  GPR00: c000001fcd93cb30 00000000cd93c840 c0000000015c5e00 00000000cd93c840
  ...
  NIP [c000000000009868] resume_kernel+0x2c/0x58
  LR [c000000000006208] program_check_common+0x108/0x180

On a 64-bit system when the user probes on a 'stdu' instruction, the kernel does
not emulate actual store in emulate_step() because it may corrupt the exception
frame. So the kernel does the actual store operation in exception return code
i.e. resume_kernel().

resume_kernel() loads the saved stack pointer from memory using lwz, which only
loads the low 32-bits of the address, causing the kernel crash.

Fix this by loading the 64-bit value instead.

Fixes: be96f63375a1 ("powerpc: Split out instruction analysis part of emulate_step()")
Signed-off-by: Ravi Bangoria 
Reviewed-by: Naveen N. Rao 
Reviewed-by: Ananth N Mavinakayanahalli 
[mpe: Change log massage, add stable tag]
Signed-off-by: Michael Ellerman 
Signed-off-by: Greg Kroah-Hartman

powerpc/tm: do not use r13 for tabort_syscall

2016-09-24T08:07:35+00:00

commit cc7786d3ee7e3c979799db834b528db2c0834c2e upstream.

tabort_syscall runs with RI=1, so a nested recoverable machine
check will load the paca into r13 and overwrite what we loaded
it with, because exceptions returning to privileged mode do not
restore r13.

Fixes: b4b56f9ecab4 (powerpc/tm: Abort syscalls in active transactions)
Signed-off-by: Nick Piggin 
Signed-off-by: Benjamin Herrenschmidt 
Signed-off-by: Greg Kroah-Hartman

powerpc/kernel: Change the do_syscall_trace_enter() API

2015-07-29T01:56:11+00:00

The API for calling do_syscall_trace_enter() is currently sensible
enough, it just returns the (modified) syscall number.

However once we enable seccomp filter it will get more complicated. When
seccomp filter runs, the seccomp kernel code (via SECCOMP_RET_ERRNO), or
a ptracer (via SECCOMP_RET_TRACE), may reject the syscall and *may* or may
*not* set a return value in r3.

That means the assembler that calls do_syscall_trace_enter() can not
blindly return ENOSYS, it needs to only return ENOSYS if a return value
has not already been set.

There is no way to implement that logic with the current API. So change
the do_syscall_trace_enter() API to make it deal with the return code
juggling, and the assembler can then just return whatever return code it
is given.

Signed-off-by: Michael Ellerman 
Reviewed-by: Kees Cook

powerpc/kernel: Switch to using MAX_ERRNO

2015-07-29T01:56:11+00:00

Currently on powerpc we have our own #define for the highest (negative)
errno value, called _LAST_ERRNO. This is defined to be 516, for reasons
which are not clear.

The generic code, and x86, use MAX_ERRNO, which is defined to be 4095.

In particular seccomp uses MAX_ERRNO to restrict the value that a
seccomp filter can return.

Currently with the mismatch between _LAST_ERRNO and MAX_ERRNO, a seccomp
tracer wanting to return 600, expecting it to be seen as an error, would
instead find on powerpc that userspace sees a successful syscall with a
return value of 600.

To avoid this inconsistency, switch powerpc to use MAX_ERRNO.

We are somewhat confident that generic syscalls that can return a
non-error value above negative MAX_ERRNO have already been updated to
use force_successful_syscall_return().

I have also checked all the powerpc specific syscalls, and believe that
none of them expect to return a non-error value between -MAX_ERRNO and
-516. So this change should be safe ...

Acked-by: Benjamin Herrenschmidt 
Signed-off-by: Michael Ellerman 
Reviewed-by: Kees Cook

powerpc/tm: Abort syscalls in active transactions

2015-06-19T07:10:28+00:00

This patch changes the syscall handler to doom (tabort) active
transactions when a syscall is made and return very early without
performing the syscall and keeping side effects to a minimum (no CPU
accounting or system call tracing is performed). Also included is a
new HWCAP2 bit, PPC_FEATURE2_HTM_NOSC, to indicate this
behaviour to userspace.

Currently, the system call instruction automatically suspends an
active transaction which causes side effects to persist when an active
transaction fails.

This does change the kernel's behaviour, but in a way that was
documented as unsupported.  It doesn't reduce functionality as
syscalls will still be performed after tsuspend; it just requires that
the transaction be explicitly suspended.  It also provides a
consistent interface and makes the behaviour of user code
substantially the same across powerpc and platforms that do not
support suspended transactions (e.g. x86 and s390).

Performance measurements using
http://ozlabs.org/~anton/junkcode/null_syscall.c indicate the cost of
a normal (non-aborted) system call increases by about 0.25%.

Signed-off-by: Sam Bobroff 
Signed-off-by: Michael Ellerman

powerpc/kernel: Rename PACA_DSCR to PACA_DSCR_DEFAULT

2015-06-07T09:29:00+00:00

PACA_DSCR offset macro tracks dscr_default element in the paca
structure. Better change the name of this macro to match that of the
data element it tracks. Makes the code more readable.

Signed-off-by: Anshuman Khandual 
Signed-off-by: Michael Ellerman

Revert "powerpc/tm: Abort syscalls in active transactions"

2015-04-30T05:24:58+00:00

This reverts commit feba40362b11341bee6d8ed58d54b896abbd9f84.

Although the principle of this change is good, the implementation has a
few issues.

Firstly we can sometimes fail to abort a syscall because r12 may have
been clobbered by C code if we went down the virtual CPU accounting
path, or if syscall tracing was enabled.

Secondly we have decided that it is safer to abort the syscall even
earlier in the syscall entry path, so that we avoid the syscall tracing
path when we are transactional.

So that we have time to thoroughly test those changes we have decided to
revert this for this merge window and will merge the fixed version in
the next window.

NB. Rather than reverting the selftest we just drop tm-syscall from
TEST_PROGS so that it's not run by default.

Fixes: feba40362b11 ("powerpc/tm: Abort syscalls in active transactions")
Signed-off-by: Michael Ellerman