linux/arch/s390
Heiko Carstens c933146a5e s390/ftrace,kprobes: allow to patch first instruction
If the function tracer is enabled, allow to set kprobes on the first
instruction of a function (which is the function trace caller):

If no kprobe is set handling of enabling and disabling function tracing
of a function simply patches the first instruction. Either it is a nop
(right now it's an unconditional branch, which skips the mcount block),
or it's a branch to the ftrace_caller() function.

If a kprobe is being placed on a function tracer calling instruction
we encode if we actually have a nop or branch in the remaining bytes
after the breakpoint instruction (illegal opcode).
This is possible, since the size of the instruction used for the nop
and branch is six bytes, while the size of the breakpoint is only
two bytes.
Therefore the first two bytes contain the illegal opcode and the last
four bytes contain either "0" for nop or "1" for branch. The kprobes
code will then execute/simulate the correct instruction.

Instruction patching for kprobes and function tracer is always done
with stop_machine(). Therefore we don't have any races where an
instruction is patched concurrently on a different cpu.
Besides that also the program check handler which executes the function
trace caller instruction won't be executed concurrently to any
stop_machine() execution.

This allows to keep full fault based kprobes handling which generates
correct pt_regs contents automatically.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
2014-10-27 13:27:27 +01:00
..
appldata s390/appldata: add slab.h for kzalloc/kfree 2014-05-20 08:58:51 +02:00
boot s390/boot: fix boot of compressed kernel built with gcc 4.9 2014-05-27 10:26:04 +02:00
configs s390: update default configuration 2014-10-27 13:27:03 +01:00
crypto crypto: s390 - fix aes,des ctr mode concurrency finding. 2014-05-08 21:46:09 +08:00
hypfs
include s390/ftrace,kprobes: allow to patch first instruction 2014-10-27 13:27:27 +01:00
kernel s390/ftrace,kprobes: allow to patch first instruction 2014-10-27 13:27:27 +01:00
kvm s390/mm: disable KSM for storage key enabled pages 2014-10-27 13:27:26 +01:00
lib s390/uprobes: fix kprobes dependency 2014-10-17 14:45:51 +02:00
math-emu
mm s390/mm: disable KSM for storage key enabled pages 2014-10-27 13:27:26 +01:00
net net: filter: constify detection of pkt_type_offset 2014-09-13 17:07:21 -04:00
oprofile s390: Replace __get_cpu_var uses 2014-08-26 13:45:52 -04:00
pci s390/pci: introduce lazy IOTLB flushing for DMA unmap 2014-07-22 09:26:24 +02:00
defconfig s390: update default configuration 2014-10-27 13:27:03 +01:00
Kbuild
Kconfig Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2014-10-14 03:47:00 +02:00
Kconfig.debug
Makefile s390: pass march flag to assembly files as well 2014-09-09 08:53:28 +02:00