From 124ec188720b6bdea85ade49e7ea195161b12fce Mon Sep 17 00:00:00 2001 From: Mike Frysinger Date: Sat, 5 Jan 2008 10:05:27 +0000 Subject: Chris Zankel writes: The following patches add support for the Xtensa processor architecture to uClibc. They are based on a recent SVN checkout (12/05/2007). The first patch (attached to this post) adds Xtensa support to various shared configuration and make files. The following patches then include the Xtensa specific files and directories. I welcome any feedback and would appreciate it if you could include the patches into the mainline tree. I am certainly committed to maintain the port. Bob Wilson was kind enough to review the patches. Some notes about the architecture: Xtensa is a configurable and extensible processor architecture developed by Tensilica. For more information, please visit: www.linux-xtensa.org. --- libc/sysdeps/linux/xtensa/__longjmp.S | 126 ++++++++++++++++++++++++++++++++++ 1 file changed, 126 insertions(+) create mode 100644 libc/sysdeps/linux/xtensa/__longjmp.S (limited to 'libc/sysdeps/linux/xtensa/__longjmp.S') diff --git a/libc/sysdeps/linux/xtensa/__longjmp.S b/libc/sysdeps/linux/xtensa/__longjmp.S new file mode 100644 index 000000000..0fa939095 --- /dev/null +++ b/libc/sysdeps/linux/xtensa/__longjmp.S @@ -0,0 +1,126 @@ +/* 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) -- cgit v1.2.3