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0ac4f1dab3
It turns out tile suffered from the same problem as S390. However, disabling CFI information for the __startcontext on tile was not sufficient to fix the problem; I think the backtracer will just blindly try to follow the link register (lr) in that case. Instead, the change adds a cfi_undefined directive for "lr" and then arranges to call __startcontext directly when the new context starts, rather than just synthesizing a return to it. In addition to being a bit easier now to understand the control flow, this also allows the cfi_undefined directive to be placed in a way that causes it to be in force at the address that the "lr" from the called function points to.
68 lines
2.0 KiB
C
68 lines
2.0 KiB
C
/* Copyright (C) 2011-2015 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library. If not, see
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<http://www.gnu.org/licenses/>. */
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <ucontext.h>
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#include <arch/abi.h>
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void
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__makecontext (ucontext_t *ucp, void (*func) (void), int argc, ...)
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{
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extern void __startcontext (void);
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uint_reg_t *sp, *args;
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va_list ap;
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int i;
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/* Initialize the top of stack. */
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sp = (uint_reg_t *) ((((intptr_t) ucp->uc_stack.ss_sp
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+ ucp->uc_stack.ss_size) & -16L) - 16);
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/* Allow room for memory-passed arguments if necessary. */
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if (argc > 10)
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sp -= 2 + (argc - 10);
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sp[0] = sp[1] = 0;
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/* Set parameters. */
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va_start (ap, argc);
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args = &ucp->uc_mcontext.gregs[0];
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for (i = 0; i < argc; i++)
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{
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if (i == 10)
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args = &sp[2];
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*args++ = va_arg (ap, long);
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}
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va_end (ap);
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/* Start in the trampoline. */
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ucp->uc_mcontext.pc = (long) __startcontext;
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/* Set stack pointer. */
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ucp->uc_mcontext.sp = (long) sp;
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/* Pass FUNC to __startcontext in r31. */
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ucp->uc_mcontext.gregs[31] = (long) func;
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/* Pass ucp->uc_link to __startcontext in r30. */
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ucp->uc_mcontext.gregs[30] = (long) ucp->uc_link;
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}
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weak_alias (__makecontext, makecontext)
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