Commit 3251f1e2 authored by Max Filippov's avatar Max Filippov
Browse files

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: default avatarMax Filippov <jcmvbkbc@gmail.com>
parent e2fd1374

arch/xtensa/kernel/entry.S

+12 −0
Original line number Diff line number Diff line
@@ -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......