https://github.com/torvalds/linux
Revision 3f74306ac84cf7f2da2fdc87014fc455f5e67bad authored by Rob Gardner on 23 December 2015, 04:16:06 UTC, committed by David S. Miller on 24 December 2015, 17:10:29 UTC
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>
1 parent 1ca04a4
Tip revision: 3f74306ac84cf7f2da2fdc87014fc455f5e67bad authored by Rob Gardner on 23 December 2015, 04:16:06 UTC
sparc64: Ensure perf can access user stacks
sparc64: Ensure perf can access user stacks
Tip revision: 3f74306
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| COPYING | -rw-r--r-- | 18.3 KB |
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| Kbuild | -rw-r--r-- | 2.6 KB |
| Kconfig | -rw-r--r-- | 252 bytes |
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| Makefile | -rw-r--r-- | 53.5 KB |
| README | -rw-r--r-- | 18.2 KB |
| REPORTING-BUGS | -rw-r--r-- | 7.3 KB |
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