2b72262b4f
I hereby relicense all my work on Sortix under the ISC license as below. All Sortix contributions by other people are already under this license, are not substantial enough to be copyrightable, or have been removed. All imported code from other projects is compatible with this license. All GPL licensed code from other projects had previously been removed. Copyright 2011-2016 Jonas 'Sortie' Termansen and contributors. Permission to use, copy, modify, and distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies. THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
108 lines
2.9 KiB
ArmAsm
108 lines
2.9 KiB
ArmAsm
/*
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* Copyright (c) 2011, 2012, 2013, 2014, 2015 Jonas 'Sortie' Termansen.
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*
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* Permission to use, copy, modify, and distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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*
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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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#include <sortix/syscall.h>
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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_NUM, %eax
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jae 3f
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1:
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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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# Zero registers to avoid information leaks.
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# eax is the return value.
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# ecx is errno.
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# edx is the return value (MIGHT NOT BE INITIALIZED, CAN LEAK!).
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# ebx is set in a moment.
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xor %esi, %esi
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xor %edi, %edi
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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 4f
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# ebx is zero in this branch.
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2:
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iretl
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3:
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# Call the null system call instead.
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xorl %eax, %eax
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jmp 1b
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4:
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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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xor %ebx, %ebx
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jmp 2b
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.size syscall_handler, .-syscall_handler
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