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authorMax Filippov <jcmvbkbc@gmail.com>2018-11-26 22:29:41 +0100
committerMax Filippov <jcmvbkbc@gmail.com>2018-11-27 03:37:47 +0100
commit2958b66694e018c552be0b60521fec27e8d12988 (patch)
tree60b3cfc5e1aa1a7f91736874a919012fa45175a2 /arch/xtensa/kernel/process.c
parentLinux 4.20-rc4 (diff)
downloadlinux-2958b66694e018c552be0b60521fec27e8d12988.tar.xz
linux-2958b66694e018c552be0b60521fec27e8d12988.zip
xtensa: enable coprocessors that are being flushed
coprocessor_flush_all may be called from a context of a thread that is different from the thread being flushed. In that case contents of the cpenable special register may not match ti->cpenable of the target thread, resulting in unhandled coprocessor exception in the kernel context. Set cpenable special register to the ti->cpenable of the target register for the duration of the flush and restore it afterwards. This fixes the following crash caused by coprocessor register inspection in native gdb: (gdb) p/x $w0 Illegal instruction in kernel: sig: 9 [#1] PREEMPT Call Trace: ___might_sleep+0x184/0x1a4 __might_sleep+0x41/0xac exit_signals+0x14/0x218 do_exit+0xc9/0x8b8 die+0x99/0xa0 do_illegal_instruction+0x18/0x6c common_exception+0x77/0x77 coprocessor_flush+0x16/0x3c arch_ptrace+0x46c/0x674 sys_ptrace+0x2ce/0x3b4 system_call+0x54/0x80 common_exception+0x77/0x77 note: gdb[100] exited with preempt_count 1 Killed Cc: stable@vger.kernel.org Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Diffstat (limited to 'arch/xtensa/kernel/process.c')
-rw-r--r--arch/xtensa/kernel/process.c5
1 files changed, 4 insertions, 1 deletions
diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c
index 483dcfb6e681..4bb68133a72a 100644
--- a/arch/xtensa/kernel/process.c
+++ b/arch/xtensa/kernel/process.c
@@ -94,18 +94,21 @@ void coprocessor_release_all(struct thread_info *ti)
void coprocessor_flush_all(struct thread_info *ti)
{
- unsigned long cpenable;
+ unsigned long cpenable, old_cpenable;
int i;
preempt_disable();
+ RSR_CPENABLE(old_cpenable);
cpenable = ti->cpenable;
+ WSR_CPENABLE(cpenable);
for (i = 0; i < XCHAL_CP_MAX; i++) {
if ((cpenable & 1) != 0 && coprocessor_owner[i] == ti)
coprocessor_flush(ti, i);
cpenable >>= 1;
}
+ WSR_CPENABLE(old_cpenable);
preempt_enable();
}