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/setjmp.S | 131 +++++++++++++++++++++++++++++++++++++ 1 file changed, 131 insertions(+) create mode 100644 libc/sysdeps/linux/xtensa/setjmp.S (limited to 'libc/sysdeps/linux/xtensa/setjmp.S') diff --git a/libc/sysdeps/linux/xtensa/setjmp.S b/libc/sysdeps/linux/xtensa/setjmp.S new file mode 100644 index 000000000..5e81460c7 --- /dev/null +++ b/libc/sysdeps/linux/xtensa/setjmp.S @@ -0,0 +1,131 @@ +/* setjmp 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" + +/* int setjmp (a2 = jmp_buf env) */ + +ENTRY (_setjmp) + movi a3, 0 + j 1f +END (_setjmp) +libc_hidden_def (_setjmp) + +ENTRY (setjmp) + movi a3, 1 + j 1f +END (setjmp) + +/* int __sigsetjmp (a2 = jmp_buf env, + a3 = int savemask) */ + +ENTRY (__sigsetjmp) +1: + /* Flush registers. */ + movi a4, __window_spill + callx4 a4 + + /* Preserve the second argument (savemask) in a15. The selection + of a15 is arbitrary, except it's otherwise unused. There is no + risk of triggering a window overflow since we just returned + from __window_spill(). */ + mov a15, a3 + + /* Copy the register save area at (sp - 16). */ + addi a5, a1, -16 + l32i a3, a5, 0 + l32i a4, a5, 4 + s32i a3, a2, 0 + s32i a4, a2, 4 + l32i a3, a5, 8 + l32i a4, a5, 12 + s32i a3, a2, 8 + s32i a4, a2, 12 + + /* Copy 0-8 words from the register overflow area. */ + extui a3, a0, 30, 2 + blti a3, 2, .Lendsj + l32i a7, a1, 4 + slli a4, a3, 4 + sub a5, a7, a4 + addi a6, a2, 16 + addi a7, a7, -16 // a7 = end of register overflow area +.Lsjloop: + l32i a3, a5, 0 + l32i a4, a5, 4 + s32i a3, a6, 0 + s32i a4, a6, 4 + l32i a3, a5, 8 + l32i a4, a5, 12 + s32i a3, a6, 8 + s32i a4, a6, 12 + addi a5, a5, 16 + addi a6, a6, 16 + blt a5, a7, .Lsjloop +.Lendsj: + + /* Copy the register save area at sp. */ + l32i a3, a1, 0 + l32i a4, a1, 4 + s32i a3, a2, 48 + s32i a4, a2, 52 + l32i a3, a1, 8 + l32i a4, a1, 12 + s32i a3, a2, 56 + s32i a4, a2, 60 + + /* Save the return address, including the window size bits. */ + s32i a0, a2, 64 + + /* a2 still addresses jmp_buf. a15 contains savemask. */ + mov a6, a2 + mov a7, a15 + movi a3, __sigjmp_save + callx4 a3 + mov a2, a6 + retw +END(__sigsetjmp) + +weak_extern(_setjmp) +weak_extern(setjmp) -- cgit v1.2.3