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authorPeter Zijlstra <peterz@infradead.org>2013-09-19 10:16:42 +0200
committerIngo Molnar <mingo@kernel.org>2013-09-20 09:45:11 +0200
commitfa7315871046b9a4c48627905691dbde57e51033 (patch)
tree89b94f609063bb4abadf354ad06afbd8c203737d /tools
parentperf/x86/intel/uncore: Don't use smp_processor_id() in validate_group() (diff)
downloadlinux-dev-fa7315871046b9a4c48627905691dbde57e51033.tar.xz
linux-dev-fa7315871046b9a4c48627905691dbde57e51033.zip
perf: Fix capabilities bitfield compatibility in 'struct perf_event_mmap_page'
Solve the problems around the broken definition of perf_event_mmap_page:: cap_usr_time and cap_usr_rdpmc fields which used to overlap, partially fixed by: 860f085b74e9 ("perf: Fix broken union in 'struct perf_event_mmap_page'") The problem with the fix (merged in v3.12-rc1 and not yet released officially), noticed by Vince Weaver is that the new behavior is not detectable by new user-space, and that due to the reuse of the field names it's easy to mis-compile a binary if old headers are used on a new kernel or new headers are used on an old kernel. To solve all that make this change explicit, detectable and self-contained, by iterating the ABI the following way: - Always clear bit 0, and rename it to usrpage->cap_bit0, to at least not confuse old user-space binaries. RDPMC will be marked as unavailable to old binaries but that's within the ABI, this is a capability bit. - Rename bit 1 to ->cap_bit0_is_deprecated and always set it to 1, so new libraries can reliably detect that bit 0 is deprecated and perma-zero without having to check the kernel version. - Use bits 2, 3, 4 for the newly defined, correct functionality: cap_user_rdpmc : 1, /* The RDPMC instruction can be used to read counts */ cap_user_time : 1, /* The time_* fields are used */ cap_user_time_zero : 1, /* The time_zero field is used */ - Rename all the bitfield names in perf_event.h to be different from the old names, to make sure it's not possible to mis-compile it accidentally with old assumptions. The 'size' field can then be used in the future to add new fields and it will act as a natural ABI version indicator as well. Also adjust tools/perf/ userspace for the new definitions, noticed by Adrian Hunter. Reported-by: Vince Weaver <vincent.weaver@maine.edu> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Also-Fixed-by: Adrian Hunter <adrian.hunter@intel.com> Link: http://lkml.kernel.org/n/tip-zr03yxjrpXesOzzupszqglbv@git.kernel.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools')
-rw-r--r--tools/perf/arch/x86/util/tsc.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/tools/perf/arch/x86/util/tsc.c b/tools/perf/arch/x86/util/tsc.c
index 9570c2b0f83c..b2519e49424f 100644
--- a/tools/perf/arch/x86/util/tsc.c
+++ b/tools/perf/arch/x86/util/tsc.c
@@ -32,7 +32,7 @@ u64 tsc_to_perf_time(u64 cyc, struct perf_tsc_conversion *tc)
int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
struct perf_tsc_conversion *tc)
{
- bool cap_usr_time_zero;
+ bool cap_user_time_zero;
u32 seq;
int i = 0;
@@ -42,7 +42,7 @@ int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
tc->time_mult = pc->time_mult;
tc->time_shift = pc->time_shift;
tc->time_zero = pc->time_zero;
- cap_usr_time_zero = pc->cap_usr_time_zero;
+ cap_user_time_zero = pc->cap_user_time_zero;
rmb();
if (pc->lock == seq && !(seq & 1))
break;
@@ -52,7 +52,7 @@ int perf_read_tsc_conversion(const struct perf_event_mmap_page *pc,
}
}
- if (!cap_usr_time_zero)
+ if (!cap_user_time_zero)
return -EOPNOTSUPP;
return 0;