linux/tools
Andi Kleen 61f611593f perf script: Fix LBR skid dump problems in brstackinsn
This is a fix for another instance of the skid problem Milian recently
found [1]

The LBRs don't freeze at the exact same time as the PMI is triggered.
The perf script brstackinsn code that dumps LBR assembler assumes that
the last branch in the LBR leads to the sample point.  But with skid
it's possible that the CPU executes one or more branches before the
sample, but which do not appear in the LBR.

What happens then is either that the sample point is before the last LBR
branch. In this case the dumper sees a negative length and ignores it.
Or it the sample point is long after the last branch. Then the dumper
sees a very long block and dumps it upto its block limit (16k bytes),
which is noise in the output.

On typical sample session this can happen regularly.

This patch tries to detect and handle the situation. On the last block
that is dumped by the LBR dumper we always stop on the first branch. If
the block length is negative just scan forward to the first branch.
Otherwise scan until a branch is found.

The PT decoder already has a function that uses the instruction decoder
to detect branches, so we can just reuse it here.

Then when a terminating branch is found print an indication and stop
dumping. This might miss a few instructions, but at least shows no
runaway blocks.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Link: http://lkml.kernel.org/r/20181120050617.4119-1-andi@firstfloor.org
[ Resolved conflict with dd2e18e9ac ("perf tools: Support 'srccode' output") ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
2018-12-28 16:33:02 -03:00
..
accounting delayacct: track delays from thrashing cache pages 2018-10-26 16:26:32 -07:00
arch tools include arch: Grab a copy of x86's prctl.h 2018-12-18 16:15:18 -03:00
bpf tools: bpftool: fix a bitfield pretty print issue 2018-11-28 16:40:02 -08:00
build perf build: Don't unconditionally link the libbfd feature test to -liberty and -lz 2018-12-21 09:42:46 -03:00
cgroup
crypto crypto: tools - Add cryptostat userspace 2018-09-28 12:46:26 +08:00
firewire
gpio
hv tools: hv: fcopy: set 'error' in case an unknown operation was requested 2018-09-30 08:49:55 -07:00
iio
include tools uapi asm: Update asm-generic/unistd.h copy 2018-12-18 16:17:41 -03:00
kvm/kvm_stat tools/kvm_stat: cut down decimal places in update interval dialog 2018-10-01 15:40:59 +02:00
laptop
leds
lib tools lib traceevent: Use LDFLAGS in the build commands 2018-12-18 12:23:57 -03:00
memory-model tools/memory-model: Add more LKMM limitations 2018-10-02 10:28:04 +02:00
nfsd
objtool objtool: Fix segfault in .cold detection with -ffunction-sections 2018-11-20 18:59:00 +01:00
pci tools: PCI: Change pcitest compiling process 2018-10-03 11:19:52 +01:00
pcmcia
perf perf script: Fix LBR skid dump problems in brstackinsn 2018-12-28 16:33:02 -03:00
power tools cpupower: Override CFLAGS assignments 2018-11-06 08:54:16 -07:00
scripts
spi
testing XArray updates for 4.20-rc7 2018-12-13 16:35:58 -08:00
thermal/tmon
time
usb usbip: tools: fix atoi() on non-null terminated string 2018-10-18 19:44:39 +02:00
virtio
vm
wmi
Makefile tools: PCI: Change pcitest compiling process 2018-10-03 11:19:52 +01:00