diff options
Diffstat (limited to 'arch/xtensa')
| -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...... |