164 lines
6.6 KiB
C
164 lines
6.6 KiB
C
/****************************************************************************
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* *
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* GNAT COMPILER COMPONENTS *
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* *
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* S I G T R A M P *
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* *
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* Asm Implementation File *
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* *
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* Copyright (C) 2015-2019, Free Software Foundation, Inc. *
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* *
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* GNAT is free software; you can redistribute it and/or modify it under *
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* terms of the GNU General Public License as published by the Free Soft- *
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* ware Foundation; either version 3, or (at your option) any later ver- *
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* sion. GNAT is distributed in the hope that it will be useful, but WITH- *
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* OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY *
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* or FITNESS FOR A PARTICULAR PURPOSE. *
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* *
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* As a special exception under Section 7 of GPL version 3, you are granted *
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* additional permissions described in the GCC Runtime Library Exception, *
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* version 3.1, as published by the Free Software Foundation. *
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* *
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* In particular, you can freely distribute your programs built with the *
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* GNAT Pro compiler, including any required library run-time units, using *
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* any licensing terms of your choosing. See the AdaCore Software License *
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* for full details. *
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* *
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* GNAT was originally developed by the GNAT team at New York University. *
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* Extensive contributions were provided by Ada Core Technologies Inc. *
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* *
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****************************************************************************/
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/******************************************************
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* ARM-Android version of the __gnat_sigtramp service *
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******************************************************/
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#include <sys/ucontext.h>
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#include "sigtramp.h"
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/* See sigtramp.h for a general explanation of functionality. */
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/* ----------------------
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-- General comments --
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----------------------
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Stubs are generated from toplevel asms,
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The general idea is to establish CFA as the sigcontext
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and state where to find the registers as offsets from there.
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We support stubs for VxWorks and Android, providing unwind info for
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common registers. We might need variants with support for floating
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point or altivec registers as well at some point.
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For Android it would be simpler to write this in Asm since there's only
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one variant, but to keep it looking like the VxWorks stubs,
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C is the choice for our toplevel interface.
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Note that the registers we "restore" here are those to which we have
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direct access through the system sigcontext structure, which includes
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only a partial set of the non-volatiles ABI-wise. */
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/* -----------------------------------------
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-- Protypes for our internal asm stubs --
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-----------------------------------------
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The registers are expected to be at SIGCONTEXT + 12 (reference the
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sicontext structure in asm/sigcontext.h which describes the first
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3 * 4byte fields.) Even though our symbols will remain local, the
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prototype claims "extern" and not "static" to prevent compiler complaints
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about a symbol used but never defined. */
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/* sigtramp stub providing unwind info for common registers. */
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extern void __gnat_sigtramp_common
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(int signo, void *siginfo, void *sigcontext,
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__sigtramphandler_t * handler);
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void __gnat_sigtramp (int signo, void *si, void *sc,
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__sigtramphandler_t * handler)
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__attribute__((optimize(2)));
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void __gnat_sigtramp (int signo, void *si, void *ucontext,
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__sigtramphandler_t * handler)
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{
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struct sigcontext *mcontext = &((ucontext_t *) ucontext)->uc_mcontext;
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__gnat_sigtramp_common (signo, si, mcontext, handler);
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}
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/* asm string construction helpers. */
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#define STR(TEXT) #TEXT
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/* stringify expanded TEXT, surrounding it with double quotes. */
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#define S(E) STR(E)
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/* stringify E, which will resolve as text but may contain macros
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still to be expanded. */
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/* asm (TEXT) outputs <tab>TEXT. These facilitate the output of
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multiline contents: */
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#define TAB(S) "\t" S
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#define CR(S) S "\n"
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#undef TCR
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#define TCR(S) TAB(CR(S))
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/* Trampoline body block
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--------------------- */
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#define SIGTRAMP_BODY \
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CR("") \
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TCR("# Allocate frame and also save r2 which is the argument register") \
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TCR("# containing the sigcontext, so that we can restore it during") \
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TCR("# unwinding and thereby load the rest of the desired context.") \
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TCR("stmfd sp!, {r2, r3, lr}") \
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TCR("# The unwinder undo's these operations in reverse order so starting") \
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TCR("# from bottom, restore r2 from the current vsp location, move r2 into") \
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TCR("# the vsp, add 12 bytes to get the start of the register save area") \
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TCR("# then restore the 15 general purpose registers of the frame which") \
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TCR("# raised the signal.") \
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TCR(".save {r0-r15}") \
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TCR(".pad #12") \
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TCR(".movsp r2") \
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TCR(".save {r2}") \
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TCR("# Call the real handler. The signo, siginfo and sigcontext") \
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TCR("# arguments are the same as those we received in r0, r1 and r2.") \
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TCR("blx r3") \
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TCR("# Restore our callee-saved items, release our frame and return") \
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TCR("# (should never get here!).") \
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TCR("ldmfd sp, {r2, r3, pc}")
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/* Symbol definition block
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----------------------- */
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#define SIGTRAMP_START(SYM) \
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CR("# " S(SYM) " unwind trampoline") \
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TCR(".type " S(SYM) ", %function") \
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CR("") \
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CR(S(SYM) ":") \
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TCR(".fnstart")
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/* Symbol termination block
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------------------------ */
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#define SIGTRAMP_END(SYM) \
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CR(".fnend") \
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TCR(".size " S(SYM) ", .-" S(SYM))
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/*----------------------------
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-- And now, the real code --
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---------------------------- */
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/* Text section start. The compiler isn't aware of that switch. */
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asm (".text\n"
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TCR(".align 2"));
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/* sigtramp stub for common registers. */
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#define TRAMP_COMMON __gnat_sigtramp_common
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asm (SIGTRAMP_START(TRAMP_COMMON));
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asm (SIGTRAMP_BODY);
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asm (SIGTRAMP_END(TRAMP_COMMON));
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