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| author | Rob Gardner <rob.gardner@oracle.com> | 2015-12-22 21:16:06 -0700 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-12-24 12:10:29 -0500 |
| commit | 3f74306ac84cf7f2da2fdc87014fc455f5e67bad (patch) | |
| tree | 84ca393a2bf06e0d8fdc085689c663697dc01e30 /arch/sparc | |
| parent | 1ca04a4ce0d5131471c5a1fac76899dc2d9d3f36 (diff) | |
| download | linux-3f74306ac84cf7f2da2fdc87014fc455f5e67bad.tar.bz2 | |
sparc64: Ensure perf can access user stacks
When an interrupt (such as a perf counter interrupt) is delivered
while executing in user space, the trap entry code puts ASI_AIUS in
%asi so that copy_from_user() and copy_to_user() will access the
correct memory. But if a perf counter interrupt is delivered while the
cpu is already executing in kernel space, then the trap entry code
will put ASI_P in %asi, and this will prevent copy_from_user() from
reading any useful stack data in either of the perf_callchain_user_X
functions, and thus no user callgraph data will be collected for this
sample period. An additional problem is that a fault is guaranteed
to occur, and though it will be silently covered up, it wastes time
and could perturb state.
In perf_callchain_user(), we ensure that %asi contains ASI_AIUS
because we know for a fact that the subsequent calls to
copy_from_user() are intended to read the user's stack.
[ Use get_fs()/set_fs() -DaveM ]
Signed-off-by: Rob Gardner <rob.gardner@oracle.com>
Signed-off-by: Dave Aldridge <david.j.aldridge@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch/sparc')
| -rw-r--r-- | arch/sparc/kernel/perf_event.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/sparc/kernel/perf_event.c b/arch/sparc/kernel/perf_event.c index 3091267c5cc3..b1144d6acffe 100644 --- a/arch/sparc/kernel/perf_event.c +++ b/arch/sparc/kernel/perf_event.c @@ -1828,11 +1828,16 @@ static void perf_callchain_user_32(struct perf_callchain_entry *entry, void perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs) { + mm_segment_t old_fs; + perf_callchain_store(entry, regs->tpc); if (!current->mm) return; + old_fs = get_fs(); + set_fs(USER_DS); + flushw_user(); pagefault_disable(); @@ -1843,4 +1848,6 @@ perf_callchain_user(struct perf_callchain_entry *entry, struct pt_regs *regs) perf_callchain_user_64(entry, regs); pagefault_enable(); + + set_fs(old_fs); } |