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57256971b0
This change implements vfork.S for direct support of the vfork syscall. clone.S is revised to correct child support for the vfork case. The main bug was creating a frame prior to the clone syscall. This was done to allow the rp and r4 registers to be saved and restored from the stack frame. r4 was used to save and restore the PIC register, r19, across the system call and the call to set errno. But in the vfork case, it is undefined behavior for the child to return from the function in which vfork was called. It is surprising that this usually worked. Syscalls on hppa save and restore rp and r19, so we don't need to create a frame prior to the clone syscall. We only need a frame when __syscall_error is called. We also don't need to save and restore r19 around the call to $$dyncall as r19 is not used in the code after $$dyncall. This considerably simplifies clone.S. Signed-off-by: John David Anglin <dave.anglin@bell.net>
130 lines
3.8 KiB
ArmAsm
130 lines
3.8 KiB
ArmAsm
/* Copyright (C) 1996-2024 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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/* clone() is even more special than fork() as it mucks with stacks
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and invokes a function in the right context after its all over. */
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#include <sysdep.h>
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#define _ERRNO_H 1
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#include <bits/errno.h>
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#include <tcb-offsets.h>
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/* Non-thread code calls __clone with the following parameters:
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int clone(int (*fn)(void *arg),
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void *child_stack,
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int flags,
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void *arg)
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NPTL Code will call __clone with the following parameters:
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int clone(int (*fn)(void *arg),
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void *child_stack,
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int flags,
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void *arg,
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int *parent_tidptr,
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struct user_desc *newtls,
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int *child_pidptr)
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The code should not mangle the extra input registers.
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Syscall expects: Input to __clone:
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4(r25) - function pointer (r26, arg0)
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0(r25) - argument (r23, arg3)
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r26 - clone flags. (r24, arg2)
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r25+64 - user stack pointer. (r25, arg1)
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r24 - parent tid pointer. (stack - 52)
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r23 - struct user_desc newtls pointer. (stack - 56)
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r22 - child tid pointer. (stack - 60)
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r20 - clone syscall number (constant)
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Return:
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On success the thread ID of the child process is returned in
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the callers context.
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On error return -1, and set errno to the value returned by
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the syscall.
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*/
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.text
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ENTRY(__clone)
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/* Sanity check arguments. */
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comib,=,n 0,%arg0,.LerrorSanity /* no NULL function pointers */
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comib,=,n 0,%arg1,.LerrorSanity /* no NULL stack pointers */
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/* Ensure stack argument is 8-byte aligned. */
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ldo 7(%r25),%r25
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depi 0,31,3,%r25
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/* Save the function pointer, arg, and flags on the new stack. */
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stwm %r26, 64(%r25)
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stw %r23, -60(%r25)
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stw %r24, -56(%r25)
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/* Clone arguments are (int flags, void * child_stack) */
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copy %r24, %r26 /* flags are first */
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/* User stack pointer is in the correct register already */
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/* Load args from stack... */
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ldw -52(%sp), %r24 /* Load parent_tidptr */
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ldw -56(%sp), %r23 /* Load newtls */
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ldw -60(%sp), %r22 /* Load child_tidptr */
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/* Do the system call */
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ble 0x100(%sr2, %r0)
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ldi __NR_clone, %r20
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ldi -4096, %r1
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comb,<<,n %r1, %ret0, .LerrorRest /* Note: unsigned compare. */
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comib,=,n 0, %ret0, .LthreadStart
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bv,n %r0(%rp)
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.LerrorRest:
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/* Something bad happened -- no child created -- need a frame */
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ldo 64(%sp),%sp
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.cfi_def_cfa_offset -64
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bl __syscall_error, %rp
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sub %r0, %ret0, %arg0
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ldw -84(%sp), %rp
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/* Return after setting errno, ret0 is set to -1 by __syscall_error. */
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bv %r0(%rp)
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ldo -64(%sp), %sp
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.LerrorSanity:
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/* Sanity checks failed, return -1, and set errno to EINVAL. */
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b .LerrorRest
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ldi -EINVAL, %ret0
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.LthreadStart:
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/* Load up the arguments. */
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ldw -60(%sp), %arg0
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ldw -64(%sp), %r22
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/* $$dyncall fixes child's PIC register */
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/* Call the user's function */
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bl $$dyncall, %r31
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copy %r31, %rp
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copy %r28, %r26
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ble 0x100(%sr2, %r0)
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ldi __NR_exit, %r20
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/* We should not return from exit.
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We do not restore r4, or the stack state. */
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iitlbp %r0, (%sr0, %r0)
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PSEUDO_END(__clone)
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libc_hidden_def (__clone)
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weak_alias (__clone, clone)
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