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sortix--sortix/sortix/x86/syscall.s
Jonas 'Sortie' Termansen 46c0cc6a12 -1 is no longer an allowed system call.
This treats a nasty bug where forking and exiting before the child
causes the kernel to panic, because the syscall -1 is run, which
just contains a trash value that happened to be 0.

The cause is still unknown. Might be the scheduler.

This won't help me sleep at night.
2011-11-22 22:08:34 +01:00

142 lines
2.9 KiB
ArmAsm

/******************************************************************************
COPYRIGHT(C) JONAS 'SORTIE' TERMANSEN 2011.
This file is part of Sortix.
Sortix is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.
Sortix 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 General Public License for more
details.
You should have received a copy of the GNU General Public License along
with Sortix. If not, see <http://www.gnu.org/licenses/>.
syscall.s
An assembly stub that acts as glue for system calls.
******************************************************************************/
.global syscall_handler
.global resume_syscall
.section .text
.type syscall_handler, @function
syscall_handler:
cli
# Compabillity with InterruptRegisters.
pushl $0x0
pushl $0x80
# Push eax, ecx, edx, ebx, esp, ebp, esi, edi
pushal
# Push the user-space data segment.
movl %ds, %ebp
pushl %ebp
# Load the kernel data segment.
movw $0x10, %bp
movl %ebp, %ds
movl %ebp, %es
movl %ebp, %fs
movl %ebp, %gs
# Compabillity with InterruptRegisters.
movl %cr2, %ebp
pushl %ebp
# Store the state structure's pointer so the call can modify it if needed.
mov %esp, syscall_state_ptr
# By default, assume the system call was complete.
movl $0, system_was_incomplete
# Reset the kernel errno.
movl $0, errno
# Make sure the requested system call is valid.
cmp SYSCALL_MAX, %eax
jb valid_eax
xorl %eax, %eax
valid_eax:
# Read a system call function pointer.
xorl %ebp, %ebp
movl syscall_list(%ebp,%eax,4), %eax
# Give the system call function the values given by user-space.
pushl %esi
pushl %edi
pushl %edx
pushl %ecx
pushl %ebx
# Call the system call.
calll *%eax
# Clean up after the call.
addl $20, %esp
# Test if the system call was incomplete
movl system_was_incomplete, %ebx
testl %ebx, %ebx
# If the system call was incomplete, the value in %eax is meaningless.
jg return_to_userspace
# The system call was completed, so store the return value.
movl %eax, 36(%esp)
# Don't forget to update userspace's errno value.
call update_userspace_errno
return_to_userspace:
# Compabillity with InterruptRegisters.
addl $4, %esp
# Restore the user-space data segment.
popl %ebp
movl %ebp, %ds
movl %ebp, %es
movl %ebp, %fs
movl %ebp, %gs
popal
# Compabillity with InterruptRegisters.
addl $8, %esp
# Return to user-space.
iretl
.type resume_syscall, @function
resume_syscall:
pushl %ebp
movl %esp, %ebp
movl 8(%esp), %eax
movl 16(%esp), %ecx
pushl 28(%ecx)
pushl 24(%ecx)
pushl 20(%ecx)
pushl 16(%ecx)
pushl 12(%ecx)
pushl 8(%ecx)
pushl 4(%ecx)
pushl 0(%ecx)
call *%eax
addl $32, %esp
leavel
retl