OpenCloudOS-Kernel/arch
Pratyush Anand 7419333fa1 arm64: kprobe: Always clear pstate.D in breakpoint exception handler
Whenever we are hitting a kprobe from a none-kprobe debug exception handler,
we hit an infinite occurrences of "Unexpected kernel single-step exception
at EL1"

PSTATE.D is debug exception mask bit. It is set whenever we enter into an
exception mode. When it is set then Watchpoint, Breakpoint, and Software
Step exceptions are masked. However, software Breakpoint Instruction
exceptions can never be masked. Therefore, if we ever execute a BRK
instruction, irrespective of D-bit setting, we will be receiving a
corresponding breakpoint exception.

For example:

- We are executing kprobe pre/post handler, and kprobe has been inserted in
  one of the instruction of a function called by handler. So, it executes
  BRK instruction and we land into the case of KPROBE_REENTER. (This case is
  already handled by current code)

- We are executing uprobe handler or any other BRK handler such as in
  WARN_ON (BRK BUG_BRK_IMM), and we trace that path using kprobe.So, we
  enter into kprobe breakpoint handler,from another BRK handler.(This case
  is not being handled currently)

In all such cases kprobe breakpoint exception will be raised when we were
already in debug exception mode. SPSR's D bit (bit 9) shows the value of
PSTATE.D immediately before the exception was taken. So, in above example
cases we would find it set in kprobe breakpoint handler.  Single step
exception will always be followed by a kprobe breakpoint exception.However,
it will only be raised gracefully if we clear D bit while returning from
breakpoint exception.  If D bit is set then, it results into undefined
exception and when it's handler enables dbg then single step exception is
generated, however it will never be handled(because address does not match
and therefore treated as unexpected).

This patch clears D-flag unconditionally in setup_singlestep, so that we can
always get single step exception correctly after returning from breakpoint
exception. Additionally, it also removes D-flag set statement for
KPROBE_REENTER return path, because debug exception for KPROBE_REENTER will
always take place in a debug exception state. So, D-flag will already be set
in this case.

Acked-by: Sandeepa Prabhu <sandeepa.s.prabhu@gmail.com>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
2016-08-25 18:00:20 +01:00
..
alpha RTC for 4.8 2016-08-05 09:48:22 -04:00
arc dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
arm DeviceTree fixes for 4.8: 2016-08-18 19:31:08 -07:00
arm64 arm64: kprobe: Always clear pstate.D in breakpoint exception handler 2016-08-25 18:00:20 +01:00
avr32 dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
blackfin dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
c6x dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
cris dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
frv RTC for 4.8 2016-08-05 09:48:22 -04:00
h8300 h8300: Add missing include file to asm/io.h 2016-08-13 08:53:56 -07:00
hexagon dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
ia64 Implements HARDENED_USERCOPY verification of copy_to_user/copy_from_user 2016-08-08 14:48:14 -07:00
m32r mm: do not pass mm_struct into handle_mm_fault 2016-07-26 16:19:19 -07:00
m68k m68knommu: fix user a5 register being overwritten 2016-08-08 12:38:47 +10:00
metag metag: Drop show_mem() from mem_init() 2016-08-09 13:41:30 +01:00
microblaze dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
mips MIPS: KVM: Propagate kseg0/mapped tlb fault errors 2016-08-12 12:01:30 +02:00
mn10300 RTC for 4.8 2016-08-05 09:48:22 -04:00
nios2 dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
openrisc dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
parisc parisc: Fix order of EREFUSED define in errno.h 2016-08-20 13:33:53 +02:00
powerpc KVM locks kvm_device list to prevent corruption on device creation. 2016-08-13 10:11:14 -07:00
s390 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2016-08-16 15:50:22 -07:00
score treewide: replace obsolete _refok by __ref 2016-08-02 17:31:41 -04:00
sh These changes improve device tree support (including builtin DTB), add 2016-08-06 09:00:05 -04:00
sparc Implements HARDENED_USERCOPY verification of copy_to_user/copy_from_user 2016-08-08 14:48:14 -07:00
tile tile: support static_key usage in non-module __exit sections 2016-08-04 08:50:07 -04:00
um Merge branch 'for-linus-4.8-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rw/uml 2016-08-04 19:37:59 -04:00
unicore32 unicore32: mm: Add missing parameter to arch_vma_access_permitted 2016-08-13 08:53:18 -07:00
x86 Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2016-08-18 15:09:41 -07:00
xtensa dma-mapping: use unsigned long for dma_attrs 2016-08-04 08:50:07 -04:00
.gitignore
Kconfig Implements HARDENED_USERCOPY verification of copy_to_user/copy_from_user 2016-08-08 14:48:14 -07:00