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This patch provides support for kprobes on branch instructions. The branch
instruction at the probed address is actually emulated and not executed
out-of-line like other normal instructions. Instead the delay-slot instruction
is copied and single stepped out of line.
At the time of probe hit, the original branch instruction is evaluated
and the target cp0_epc is computed similar to compute_retrun_epc(). It
is also checked if the delay slot instruction can be skipped, which is
true if there is a NOP in delay slot or branch is taken in case of
branch likely instructions. Once the delay slot instruction is single
stepped the normal execution resume with the cp0_epc updated the earlier
computed cp0_epc as per the branch instructions.
Signed-off-by: Maneesh Soni <manesoni@cisco.com>
Signed-off-by: Victor Kamensky <kamensky@cisco.com>
Cc: David Daney <david.daney@cavium.com>
Cc: ananth@in.ibm.com
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2914/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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As ll/sc instruction are for atomic read-modify-write operations, allowing
probes on top of these insturctions is a bad idea.
Signed-off-by: Victor Kamensky <kamensky@cisco.com>
Signed-off-by: Maneesh Soni <manesoni@cisco.com>
Cc: David Daney <david.daney@cavium.com>
Cc: ananth@in.ibm.com
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2912/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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This patch fixes the arch_prepare_kprobe() on MIPS when it tries to find the
instruction at the previous address to the probed address. The oops happens
when the probed address is the first address in a kernel module and there is
no previous address. The patch uses probe_kernel_read() to safely read the
previous instruction.
CPU 3 Unable to handle kernel paging request at virtual address ffffffffc0211ffc, epc == ffffffff81113204, ra == ffffffff8111511c
Oops[#1]:
Cpu 3
$ 0 : 0000000000000000 0000000000000001 ffffffffc0212000 0000000000000000
$ 4 : ffffffffc0220030 0000000000000000 0000000000000adf ffffffff81a3f898
$ 8 : ffffffffc0220030 ffffffffffffffff 000000000000ffff 0000000000004821
$12 : 000000000000000a ffffffff81105ddc ffffffff812927d0 0000000000000000
$16 : ffffffff81a40000 ffffffffc0220030 ffffffffc0220030 ffffffffc0212660
$20 : 0000000000000000 0000000000000008 efffffffffffffff ffffffffc0220000
$24 : 0000000000000002 ffffffff8139f5b0
$28 : a800000072adc000 a800000072adfca0 ffffffffc0220000 ffffffff8111511c
Hi : 0000000000000000
Lo : 0000000000000000
epc : ffffffff81113204 arch_prepare_kprobe+0x1c/0xe8
Tainted: P
ra : ffffffff8111511c register_kprobe+0x33c/0x730
Status: 10008ce3 KX SX UX KERNEL EXL IE
Cause : 00800008
BadVA : ffffffffc0211ffc
PrId : 000d9008 (Cavium Octeon II)
Modules linked in: bpa_mem crashinfo pds tun cpumem ipv6 exportfs nfsd OOBnd(P) OOBhal(P) cvmx_mdio cvmx_gpio aipcmod(P) mtsmod procfs(P) utaker_mod dplr_pci hello atomicm_foo [last unloaded: sysmgr_hb]
Process stapio (pid: 5603, threadinfo=a800000072adc000, task=a8000000722e0438, tls=000000002b4bcda0)
Stack : ffffffff81a40000 ffffffff81a40000 ffffffffc0220030 ffffffff8111511c
ffffffffc0218008 0000000000000001 ffffffffc0218008 0000000000000001
ffffffffc0220000 ffffffffc021efe8 1000000000000000 0000000000000008
efffffffffffffff ffffffffc0220000 ffffffffc0220000 ffffffffc021d500
0000000000000022 0000000000000002 1111000072be02b8 0000000000000000
00000000000015e6 00000000000015e6 00000000007d0f00 a800000072be02b8
0000000000000000 ffffffff811d16c8 a80000000382e3b0 ffffffff811d5ba0
ffffffff81b0a270 ffffffff81b0a270 ffffffffc0212000 0000000000000013
ffffffffc0220030 ffffffffc021ed00 a800000089114c80 000000007f90d590
a800000072adfe38 a800000089114c80 0000000010020000 0000000010020000
...
Call Trace:
[<ffffffff81113204>] arch_prepare_kprobe+0x1c/0xe8
[<ffffffff8111511c>] register_kprobe+0x33c/0x730
[<ffffffffc021d500>] _stp_ctl_write_cmd+0x8e8/0xa88 [atomicm_foo]
[<ffffffff812925cc>] vfs_write+0xb4/0x178
[<ffffffff81292828>] SyS_write+0x58/0x148
[<ffffffff81103844>] handle_sysn32+0x44/0x84
Code: ffb20010 ffb00000 dc820028 <8c44fffc> 8c500000 0c4449e0 0004203c 14400029 3c048199
Signed-off-by: Maneesh Soni <manesoni@cisco.com>
Signed-off-by: Victor Kamensky <kamensky@cisco.com>
Cc: David Daney <david.daney@cavium.com>
Cc: ananth@in.ibm.com
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2915/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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This patch is based on previous work by Sony and Himanshu Chauhan.
I have done some cleanup and implemented JProbes and KRETPROBES. The
KRETPROBES part is pretty much copied verbatim from powerpc. A possible
future enhance might be to factor out the common code.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Cc: Himanshu Chauhan <hschauhan@nulltrace.org>
To: linux-mips@linux-mips.org
To: ananth@in.ibm.com,
To: anil.s.keshavamurthy@intel.com
To: davem@davemloft.net
To: masami.hiramatsu.pt@hitachi.com
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/1525/
Patchwork: https://patchwork.linux-mips.org/patch/1530/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
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