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664f565f9c
So far if the ucontext structure was obtained by getcontext and co, the return address was stored in general purpose register 14 as it is defined as return address in the ABI. In contrast, the context passed to a signal handler contains the address in psw.addr field. If somebody e.g. wants to dump the address of the context, the origin needs to be known. Now this patch adjusts getcontext and friends and stores the return address also in psw.addr field. Note that setcontext isn't adjusted and it is not supported to pass a ucontext structure from signal-handler to setcontext. We are not able to restore all registers and branching to psw.addr without clobbering one register.
100 lines
3.3 KiB
C
100 lines
3.3 KiB
C
/* Copyright (C) 2001-2023 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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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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<https://www.gnu.org/licenses/>. */
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#include <libintl.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <ucontext.h>
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/* This implementation can handle any ARGC value but only
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normal integer type parameters. Parameters of type float,
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double, complex and structure with sizes 0, 2, 4 or 8
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won't work.
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makecontext sets up a stack and the registers for the
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user context. The stack looks like this:
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size offset
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%r15 -> +-----------------------+
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8 | back chain (zero) | 0
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8 | reserved | 8
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144 | save area for (*func) | 16
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+-----------------------+
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n | overflow parameters | 160
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+-----------------------+
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The registers are set up like this:
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%r2-%r6: parameters 1 to 5
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%r7 : (*func) pointer
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%r8 : uc_link from ucontext structure
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%r9 : address of setcontext
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%r14 : return address to uc_link trampoline
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%r15 : stack pointer.
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The trampoline looks like this:
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basr %r14,%r7
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lgr %r2,%r8
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br %r9. */
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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 __makecontext_ret (void);
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unsigned long int *sp;
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va_list ap;
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sp = (unsigned long int *) (((unsigned long int) ucp->uc_stack.ss_sp
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+ ucp->uc_stack.ss_size) & -8L);
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/* Set the return address to trampoline. */
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ucp->uc_mcontext.gregs[14] = (long int) __makecontext_ret;
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/* Store psw mask to 0x0 and addr to trampoline. Then the address
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can be retrieved from the ucontext structure in the same way as if it
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is created by kernel and passed to a signal-handler. */
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ucp->uc_mcontext.psw.addr = (long int) __makecontext_ret;
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ucp->uc_mcontext.psw.mask = 0;
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/* Set register parameters. */
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va_start (ap, argc);
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for (int i = 0; i < argc && i < 5; ++i)
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ucp->uc_mcontext.gregs[2 + i] = va_arg (ap, long int);
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/* The remaining arguments go to the overflow area. */
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if (argc > 5)
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{
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sp -= argc - 5;
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for (int i = 5; i < argc; ++i)
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sp[i - 5] = va_arg (ap, long int);
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}
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va_end (ap);
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/* Make room for the save area and set the backchain. */
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sp -= 20;
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*sp = 0;
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/* Pass (*func) to __makecontext_ret in %r7. */
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ucp->uc_mcontext.gregs[7] = (long int) func;
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/* Pass ucp->uc_link to __makecontext_ret in %r8. */
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ucp->uc_mcontext.gregs[8] = (long int) ucp->uc_link;
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/* Pass address of setcontext in %r9. */
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ucp->uc_mcontext.gregs[9] = (long int) &setcontext;
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/* Set stack pointer. */
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ucp->uc_mcontext.gregs[15] = (long int) sp;
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}
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weak_alias (__makecontext, makecontext)
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