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diff --git a/libc/sysdeps/linux/xtensa/__longjmp.S b/libc/sysdeps/linux/xtensa/__longjmp.S
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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, write to the Free
+ Software Foundation, Inc., 51 Franklin Street - Fifth Floor,
+ Boston, MA 02110-1301, USA. */
+
+/* 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)