From 974802eaa1afdc87e00821df7020a2b3c6fee623 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 12 Jun 2009 12:46:55 +0200 Subject: perf_counter: Add forward/backward attribute ABI compatibility Provide for means of extending the perf_counter_attr in a 'natural' way. We allow growing the structure by appending fields at the end by specifying the full structure size inside it. When a new kernel sees a smaller (old) structure, it will 0 pad the tail. When an old kernel sees a larger (new) structure, it will verify the tail consists of 0s, otherwise fail. If we fail due to a size-mismatch, we return -E2BIG and write the kernel's native attribe size back into the provided structure. Furthermore, add some attribute verification, so that we'll fail counter creation when unknown bits are present (PERF_SAMPLE, PERF_FORMAT, or in the __reserved fields). (This ABI detail is introduced while keeping the existing syscall ABI.) Signed-off-by: Peter Zijlstra Cc: Mike Galbraith Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo LKML-Reference: Signed-off-by: Ingo Molnar --- tools/perf/perf.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'tools/perf/perf.h') diff --git a/tools/perf/perf.h b/tools/perf/perf.h index af0a5046d743..87a1aca4a424 100644 --- a/tools/perf/perf.h +++ b/tools/perf/perf.h @@ -53,11 +53,12 @@ static inline unsigned long long rdclock(void) _min1 < _min2 ? _min1 : _min2; }) static inline int -sys_perf_counter_open(struct perf_counter_attr *attr_uptr, +sys_perf_counter_open(struct perf_counter_attr *attr, pid_t pid, int cpu, int group_fd, unsigned long flags) { - return syscall(__NR_perf_counter_open, attr_uptr, pid, cpu, + attr->size = sizeof(*attr); + return syscall(__NR_perf_counter_open, attr, pid, cpu, group_fd, flags); } -- cgit v1.2.3