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authorRavi Bangoria <ravi.bangoria@linux.vnet.ibm.com>2017-06-15 19:16:48 +0530
committerMichael Ellerman <mpe@ellerman.id.au>2017-06-16 21:02:46 +1000
commitbf05fc25f268cd62f147f368fe65ad3e5b04fe9f (patch)
tree27424c2ed8c2ec5aba358a6b53e82458c56a244b /arch
parentd89ba5353f301971dd7d2f9fdf25c4432728f38e (diff)
downloadlinux-bf05fc25f268cd62f147f368fe65ad3e5b04fe9f.tar.bz2
powerpc/perf: Fix oops when kthread execs user process
When a kthread calls call_usermodehelper() the steps are: 1. allocate current->mm 2. load_elf_binary() 3. populate current->thread.regs While doing this, interrupts are not disabled. If there is a perf interrupt in the middle of this process (i.e. step 1 has completed but not yet reached to step 3) and if perf tries to read userspace regs, kernel oops with following log: Unable to handle kernel paging request for data at address 0x00000000 Faulting instruction address: 0xc0000000000da0fc ... Call Trace: perf_output_sample_regs+0x6c/0xd0 perf_output_sample+0x4e4/0x830 perf_event_output_forward+0x64/0x90 __perf_event_overflow+0x8c/0x1e0 record_and_restart+0x220/0x5c0 perf_event_interrupt+0x2d8/0x4d0 performance_monitor_exception+0x54/0x70 performance_monitor_common+0x158/0x160 --- interrupt: f01 at avtab_search_node+0x150/0x1a0 LR = avtab_search_node+0x100/0x1a0 ... load_elf_binary+0x6e8/0x15a0 search_binary_handler+0xe8/0x290 do_execveat_common.isra.14+0x5f4/0x840 call_usermodehelper_exec_async+0x170/0x210 ret_from_kernel_thread+0x5c/0x7c Fix it by setting abi to PERF_SAMPLE_REGS_ABI_NONE when userspace pt_regs are not set. Fixes: ed4a4ef85cf5 ("powerpc/perf: Add support for sampling interrupt register state") Cc: stable@vger.kernel.org # v4.7+ Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com> Acked-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch')
-rw-r--r--arch/powerpc/perf/perf_regs.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/powerpc/perf/perf_regs.c b/arch/powerpc/perf/perf_regs.c
index cbd82fde5770..09ceea6175ba 100644
--- a/arch/powerpc/perf/perf_regs.c
+++ b/arch/powerpc/perf/perf_regs.c
@@ -101,5 +101,6 @@ void perf_get_regs_user(struct perf_regs *regs_user,
struct pt_regs *regs_user_copy)
{
regs_user->regs = task_pt_regs(current);
- regs_user->abi = perf_reg_abi(current);
+ regs_user->abi = (regs_user->regs) ? perf_reg_abi(current) :
+ PERF_SAMPLE_REGS_ABI_NONE;
}