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sortix--sortix/sortix/x86/syscall.s
2013-12-17 14:30:35 +01:00

104 lines
2.8 KiB
ArmAsm

/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013.
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/>.
x86/syscall.s
An assembly stub that acts as glue for system calls.
*******************************************************************************/
.global syscall_handler
.section .text
.type syscall_handler, @function
syscall_handler:
# The processor disabled interrupts during the int $0x80 instruction,
# however Sortix system calls runs with interrupts enabled such that they
# can be pre-empted.
sti
movl $0, global_errno # Reset errno
pushl %ebp
# Grant ourselves kernel permissions to the data segment.
movl %ds, %ebp
pushl %ebp
movw $0x10, %bp
movl %ebp, %ds
movl %ebp, %es
movl %ebp, %fs
movl %ebp, %gs
# Make sure the requested system call is valid.
cmp SYSCALL_MAX, %eax
jae fix_syscall
valid_syscall:
# Read a system call function pointer.
xorl %ebp, %ebp
movl syscall_list(%ebp,%eax,4), %eax
# Point the %ebp register to the pushed user-space %ebp above.
movl %esp, %ebp
addl $4, %ebp
# Call the system call.
pushl %esi
pushl %edi
pushl %edx
pushl %ecx
pushl %ebx
calll *%eax
addl $20, %esp
# Restore the previous permissions to data segment.
popl %ebp
movl %ebp, %ds
movl %ebp, %es
movl %ebp, %fs
movl %ebp, %gs
# Return to user-space, system call result in %eax:%edx, errno in %ecx.
popl %ebp
movl global_errno, %ecx
# If any signals are pending, fire them now.
movl asm_signal_is_pending, %ebx
testl %ebx, %ebx
jnz call_signal_dispatcher
iretl
fix_syscall:
# Call the null system call instead.
xorl %eax, %eax
jmp valid_syscall
call_signal_dispatcher:
# We can't return to this location after the signal, since if any system
# call is made this stack will get reused and all our nice temporaries wil
# be garbage. We therefore pass the kernel the state to return to and it'll
# handle it for us when the signal is over.
movl %esp, %ebx
int $130 # Deliver pending signals.
# If we end up here, it means that the signal didn't override anything and
# that we should just go ahead and return to userspace ourselves.
iretl
.size syscall_handler, .-syscall_handler