From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 18 Aug 2016 18:21:46 +0000 (-0400)
Subject: Fix: perf counters build against kernel headers < 3.12
X-Git-Tag: v2.9.0-rc1~24
X-Git-Url: http://git.liburcu.org/?a=commitdiff_plain;h=77d7fa989f79f3c2cb14d26576cbbb54b0637594;hp=77d7fa989f79f3c2cb14d26576cbbb54b0637594;p=lttng-ust.git

Fix: perf counters build against kernel headers < 3.12

Copy Linux kernel perf_event.h installed headers into lttng-ust to know
the recent ABI layout, and use the bit description detailed in the
following Linux kernel commit:

https://github.com/torvalds/linux/commit/fa7315871046b9a4c48627905691dbde57e51033

to check whether the kernel supports rdpmc.

Fall-back on the perf read system call for kernels prior to 3.12,
because older kernels have an ABI bug where a union was used for both
cap_usr_time and cap_usr_rdpmc.

Ensure setup_perf set the pc pointer value before checking whether we
need to the file descriptor open or not.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---