linux/arch/powerpc
Naveen N. Rao f558b37bf4 powerpc/optprobes: Fix TOC handling in optprobes trampoline
Optprobes on powerpc are limited to kernel text area. We decided to also
optimize kretprobe_trampoline since that is also in kernel text area.
However,we failed to take into consideration the fact that the same
trampoline is also used to catch function returns from kernel modules.
As an example:

  $ sudo modprobe kobject-example
  $ sudo bash -c "echo 'r foo_show+8' > /sys/kernel/debug/tracing/kprobe_events"
  $ sudo bash -c "echo 1 > /sys/kernel/debug/tracing/events/kprobes/enable"
  $ sudo cat /sys/kernel/debug/kprobes/list
  c000000000041350  k  kretprobe_trampoline+0x0    [OPTIMIZED]
  d000000000e00200  r  foo_show+0x8  kobject_example
  $ cat /sys/kernel/kobject_example/foo
  Segmentation fault

With the below (trimmed) splat in dmesg:

  Unable to handle kernel paging request for data at address 0xfec40000
  Faulting instruction address: 0xc000000000041540
  Oops: Kernel access of bad area, sig: 11 [#1]
  ...
  NIP [c000000000041540] optimized_callback+0x70/0xe0
  LR [c000000000041e60] optinsn_slot+0xf8/0x10000
  Call Trace:
  [c0000000c7327850] [c000000000289af4] alloc_set_pte+0x1c4/0x860 (unreliable)
  [c0000000c7327890] [c000000000041e60] optinsn_slot+0xf8/0x10000
  --- interrupt: 700 at 0xc0000000c7327a80
	       LR = kretprobe_trampoline+0x0/0x10
  [c0000000c7327ba0] [c0000000003a30d4] sysfs_kf_seq_show+0x104/0x1d0
  [c0000000c7327bf0] [c0000000003a0bb4] kernfs_seq_show+0x44/0x60
  [c0000000c7327c10] [c000000000330578] seq_read+0xf8/0x560
  [c0000000c7327cb0] [c0000000003a1e64] kernfs_fop_read+0x194/0x260
  [c0000000c7327d00] [c0000000002f9954] __vfs_read+0x44/0x1a0
  [c0000000c7327d90] [c0000000002fb4cc] vfs_read+0xbc/0x1b0
  [c0000000c7327de0] [c0000000002fd138] SyS_read+0x68/0x110
  [c0000000c7327e30] [c00000000000b8e0] system_call+0x38/0xfc

Fix this by loading up the kernel TOC before calling into the kernel.
The original TOC gets restored as part of the usual pt_regs restore.

Fixes: 762df10bad ("powerpc/kprobes: Optimize kprobe in kretprobe_trampoline()")
Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
2017-02-23 08:23:30 +11:00
..
boot Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/scottwood/linux into next 2017-02-18 21:37:14 +11:00
configs powerpc/pseries: Revert 'Auto-online hotplugged memory' 2017-02-21 12:57:01 +11:00
crypto crypto: crc32c-vpmsum - Rename CRYPT_CRC32C_VPMSUM option 2016-11-28 21:23:17 +08:00
include powerpc/pseries: Advertise Hot Plug Event support to firmware 2017-02-21 21:32:53 +11:00
kernel powerpc/optprobes: Fix TOC handling in optprobes trampoline 2017-02-23 08:23:30 +11:00
kvm powerpc/powernv: Remove separate entry for OPAL real mode calls 2017-02-07 16:40:18 +11:00
lib powerpc/kprobes: Implement Optprobes 2017-02-10 13:28:04 +11:00
math-emu Replace <asm/uaccess.h> with <linux/uaccess.h> globally 2016-12-24 11:46:01 -08:00
mm powerpc/mm: Fix typo in set_pte_at() 2017-02-17 22:16:25 +11:00
net powerpc/bpf: Introduce __PPC_SH64() 2017-02-10 13:28:03 +11:00
oprofile ktime: Cleanup ktime_set() usage 2016-12-25 17:21:22 +01:00
perf Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/scottwood/linux into next 2017-02-18 21:37:14 +11:00
platforms powerpc/pseries: Revert 'Auto-online hotplugged memory' 2017-02-21 12:57:01 +11:00
purgatory powerpc: Add purgatory for kexec_file_load() implementation. 2016-11-30 23:15:26 +11:00
scripts powerpc/ftrace: Add Kconfig & Make glue for mprofile-kernel 2016-03-07 14:53:56 +11:00
sysdev powerpc/icp-opal: Fix missing KVM case and harden replay 2017-01-17 11:50:03 +11:00
xmon powerpc/xmon: Dump memory in CPU endian format 2017-02-21 16:00:21 +11:00
Kconfig Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/scottwood/linux into next 2017-02-18 21:37:14 +11:00
Kconfig.debug powerpc/xmon: Enable disassembly files (compilation changes) 2017-02-15 20:02:42 +11:00
Makefile powerpc: Add purgatory for kexec_file_load() implementation. 2016-11-30 23:15:26 +11:00
relocs_check.sh powerpc/64: whitelist unresolved modversions CRCs 2016-09-22 14:46:31 +02:00