diff options
| author | Max Filippov <jcmvbkbc@gmail.com> | 2013-10-30 16:18:25 +0400 |
|---|---|---|
| committer | Max Filippov <jcmvbkbc@gmail.com> | 2014-01-25 23:24:38 +0400 |
| commit | 3251f1e27a5a17f0efd436cfd1e7b9896cfab0a0 (patch) | |
| tree | bbc623531e4ef45620b84d37ca5325605b12c2f4 /arch/xtensa/kernel | |
| parent | e2fd1374c705abe4661df3fb6fadb3879c7c1846 (diff) | |
xtensa: save current register frame in fast_syscall_spill_registers_fixup
We need it saved because it contains a3 where we track which register
windows we still need to spill, and fixup handler may call C exception
handlers. Also fix comments.
Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Diffstat (limited to 'arch/xtensa/kernel')
| -rw-r--r-- | arch/xtensa/kernel/entry.S | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/xtensa/kernel/entry.S b/arch/xtensa/kernel/entry.S index 0489918e40d2..b61e25146a2f 100644 --- a/arch/xtensa/kernel/entry.S +++ b/arch/xtensa/kernel/entry.S @@ -1117,6 +1117,13 @@ ENDPROC(fast_syscall_spill_registers) * We basically restore WINDOWBASE and WINDOWSTART to the condition when * we entered the spill routine and jump to the user exception handler. * + * Note that we only need to restore the bits in windowstart that have not + * been spilled yet by the _spill_register routine. Luckily, a3 contains a + * rotated windowstart with only those bits set for frames that haven't been + * spilled yet. Because a3 is rotated such that bit 0 represents the register + * frame for the current windowbase - 1, we need to rotate a3 left by the + * value of the current windowbase + 1 and move it to windowstart. + * * a0: value of depc, original value in depc * a2: trashed, original value in EXC_TABLE_DOUBLE_SAVE * a3: exctable, original value in excsave1 @@ -1131,10 +1138,15 @@ ENTRY(fast_syscall_spill_registers_fixup) /* We need to make sure the current registers (a0-a3) are preserved. * To do this, we simply set the bit for the current window frame * in WS, so that the exception handlers save them to the task stack. + * + * Note: we use a3 to set the windowbase, so we take a special care + * of it, saving it in the original _spill_registers frame across + * the exception handler call. */ xsr a3, excsave1 # get spill-mask slli a3, a3, 1 # shift left by one + addi a3, a3, 1 # set the bit for the current window frame slli a2, a3, 32-WSBITS src a2, a3, a2 # a2 = xxwww1yyxxxwww1yy...... |