101 lines
2.8 KiB
ArmAsm
101 lines
2.8 KiB
ArmAsm
/*******************************************************************************
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Copyright(C) Jonas 'Sortie' Termansen 2011, 2012, 2013, 2014.
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This file is part of Sortix.
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Sortix is free software: you can redistribute it and/or modify it under the
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terms of the GNU General Public License as published by the Free Software
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Foundation, either version 3 of the License, or (at your option) any later
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version.
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Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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details.
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You should have received a copy of the GNU General Public License along with
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Sortix. If not, see <http://www.gnu.org/licenses/>.
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x86/syscall.S
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An assembly stub that acts as glue for system calls.
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*******************************************************************************/
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.global syscall_handler
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.section .text
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.type syscall_handler, @function
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syscall_handler:
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/* -- stack is 12 bytes from being 16-byte aligned -- */
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movl $0, global_errno # Reset errno
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pushl %ebp
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/* -- stack is 8 bytes from being 16-byte aligned -- */
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# Grant ourselves kernel permissions to the data segment.
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movl %ds, %ebp
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pushl %ebp
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/* -- stack is 4 bytes from being 16-byte aligned -- */
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movw $0x10, %bp
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movl %ebp, %ds
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movl %ebp, %es
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# Make sure the requested system call is valid.
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cmp SYSCALL_MAX, %eax
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jae fix_syscall
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valid_syscall:
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# Read a system call function pointer.
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xorl %ebp, %ebp
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movl syscall_list(%ebp,%eax,4), %eax
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# Point the %ebp register to the pushed user-space %ebp above.
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movl %esp, %ebp
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addl $4, %ebp
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# Call the system call.
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pushl %esi
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/* -- stack is 16-byte aligned -- */
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pushl %edi
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pushl %edx
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pushl %ecx
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pushl %ebx
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/* -- stack is 16-byte aligned -- */
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calll *%eax
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addl $20, %esp
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# Restore the previous permissions to data segment.
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popl %ebp
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movl %ebp, %ds
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movl %ebp, %es
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# Return to user-space, system call result in %eax:%edx, errno in %ecx.
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popl %ebp
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movl global_errno, %ecx
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# If any signals are pending, fire them now.
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movl asm_signal_is_pending, %ebx
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testl %ebx, %ebx
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jnz call_signal_dispatcher
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iretl
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fix_syscall:
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# Call the null system call instead.
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xorl %eax, %eax
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jmp valid_syscall
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call_signal_dispatcher:
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# We can't return to this location after the signal, since if any system
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# call is made this stack will get reused and all our nice temporaries wil
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# be garbage. We therefore pass the kernel the state to return to and it'll
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# handle it for us when the signal is over.
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movl %esp, %ebx
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int $130 # Deliver pending signals.
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# If we end up here, it means that the signal didn't override anything and
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# that we should just go ahead and return to userspace ourselves.
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iretl
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.size syscall_handler, .-syscall_handler
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