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- /* longjmp for Xtensa Processors.
- Copyright (C) 2001, 2007 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
- The GNU C Library is distributed in the hope that it will be useful,
- but WITHOUT ANY WARRANTY; without even the implied warranty of
- MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; if not, see
- <http://www.gnu.org/licenses/>. */
- /* This implementation relies heavily on the Xtensa register window
- mechanism. Setjmp flushes all the windows except its own to the
- stack and then copies registers from the save areas on the stack
- into the jmp_buf structure, along with the return address of the call
- to setjmp. Longjmp invalidates all the windows except its own, and
- then sets things up so that it will return to the right place,
- using a window underflow to automatically restore the registers.
- Note that it would probably be sufficient to only copy the
- registers from setjmp's caller into jmp_buf. However, we also copy
- the save area located at the stack pointer of setjmp's caller.
- This save area will typically remain intact until the longjmp call.
- The one exception is when there is an intervening alloca in
- setjmp's caller. This is certainly an unusual situation and is
- likely to cause problems in any case (the storage allocated on the
- stack cannot be safely accessed following the longjmp). As bad as
- it is, on most systems this situation would not necessarily lead to
- a catastrophic failure. If we did not preserve the extra save area
- on Xtensa, however, it would. When setjmp's caller returns after a
- longjmp, there will be a window underflow; an invalid return
- address or stack pointer in the save area will almost certainly
- lead to a crash. Keeping a copy of the extra save area in the
- jmp_buf avoids this with only a small additional cost. If setjmp
- and longjmp are ever time-critical, this could be removed. */
- #include "sysdep.h"
- ENTRY (__longjmp)
- /* Invalidate all but the current window. Reading and writing
- special registers WINDOWBASE and WINDOWSTART are
- privileged operations, so user processes must call the
- slower __window_spill() to do the job. */
- movi a4, __window_spill
- callx4 a4
- /* Return to the return address of the setjmp, using the
- window size bits from the setjmp call so that the caller
- will be able to find the return value that we put in a2. */
- l32i a0, a2, 64
- /* Copy the first 4 saved registers from jmp_buf into the save area
- at the current sp so that the values will be restored to registers
- when longjmp returns. */
- addi a7, a1, -16
- l32i a4, a2, 0
- l32i a5, a2, 4
- s32i a4, a7, 0
- s32i a5, a7, 4
- l32i a4, a2, 8
- l32i a5, a2, 12
- s32i a4, a7, 8
- s32i a5, a7, 12
- /* Copy the remaining 0-8 saved registers. */
- extui a7, a0, 30, 2
- blti a7, 2, .Lendlj
- l32i a8, a2, 52
- slli a4, a7, 4
- sub a6, a8, a4
- addi a5, a2, 16
- addi a8, a8, -16 /* a8 = end of register overflow area */
- .Lljloop:
- l32i a7, a5, 0
- l32i a4, a5, 4
- s32i a7, a6, 0
- s32i a4, a6, 4
- l32i a7, a5, 8
- l32i a4, a5, 12
- s32i a7, a6, 8
- s32i a4, a6, 12
- addi a5, a5, 16
- addi a6, a6, 16
- blt a6, a8, .Lljloop
- .Lendlj:
- /* The 4 words saved from the register save area at the target's
- sp are copied back to the target procedure's save area. The
- only point of this is to prevent a catastrophic failure in
- case the contents were moved by an alloca after calling
- setjmp. This is a bit paranoid but it doesn't cost much. */
- l32i a7, a2, 4 /* load the target stack pointer */
- addi a7, a7, -16 /* find the destination save area */
- l32i a4, a2, 48
- l32i a5, a2, 52
- s32i a4, a7, 0
- s32i a5, a7, 4
- l32i a4, a2, 56
- l32i a5, a2, 60
- s32i a4, a7, 8
- s32i a5, a7, 12
- /* Return v ? v : 1. */
- movi a2, 1
- movnez a2, a3, a3
- retw
- END (__longjmp)
- libc_hidden_def (__longjmp)
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