mirror of
https://gitlab.com/sortix/sortix.git
synced 2023-02-13 20:55:38 -05:00
94 lines
2.7 KiB
ArmAsm
94 lines
2.7 KiB
ArmAsm
/*
|
|
* Copyright (c) 2011, 2012, 2013, 2014, 2015 Jonas 'Sortie' Termansen.
|
|
*
|
|
* 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.
|
|
*
|
|
* x64/syscall.S
|
|
* An assembly stub that acts as glue for system calls.
|
|
*/
|
|
|
|
#include <sortix/syscall.h>
|
|
|
|
.global syscall_handler
|
|
|
|
.section .text
|
|
.type syscall_handler, @function
|
|
syscall_handler:
|
|
cld
|
|
movl $0, errno
|
|
|
|
pushq %rbp
|
|
movq %rsp, %rbp
|
|
|
|
# Make sure the requested system call is valid, if not, then fix it.
|
|
cmp $SYSCALL_MAX_NUM, %rax
|
|
jae 3f
|
|
|
|
1:
|
|
# Read a system call function pointer.
|
|
xorq %r11, %r11
|
|
movq syscall_list(%r11,%rax,8), %rax
|
|
|
|
# Oh how nice, user-space put the parameters in: rdi, rsi, rdx, rcx, r8, r9
|
|
|
|
# Call the system call.
|
|
callq *%rax
|
|
|
|
# Return to user-space, system call result in %rax:%rdx, errno in %ecx.
|
|
popq %rbp
|
|
movl errno, %ecx
|
|
|
|
# Zero registers to avoid information leaks.
|
|
# rax is return value.
|
|
# rdi is set in a moment.
|
|
xor %rsi, %rsi
|
|
# rdx is return value (MIGHT NOT BE INITIALIZED, CAN LEAK!).
|
|
# rcx is errno.
|
|
xor %r8, %r8
|
|
xor %r9, %r9
|
|
xor %r10, %r10
|
|
xor %r11, %r11
|
|
# The rest of the registers are preserved by the ABI and syscall ABI.
|
|
|
|
# If any signals are pending, fire them now.
|
|
movq asm_signal_is_pending, %rdi
|
|
testq %rdi, %rdi
|
|
jnz 4f
|
|
# rdi is zero in this branch.
|
|
|
|
2:
|
|
iretq
|
|
|
|
3:
|
|
# Call the null system call instead.
|
|
xorq %rax, %rax
|
|
jmp 1b
|
|
|
|
4:
|
|
# 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.
|
|
movq 0(%rsp), %rdi # userspace rip
|
|
movq 16(%rsp), %rsi # userspace rflags
|
|
movq 24(%rsp), %r8 # userspace rsp, note %rcx is used for errno
|
|
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. Zero the
|
|
# scratch registers to avoid information leaks.
|
|
xor %rdi, %rdi
|
|
xor %rsi, %rsi
|
|
xor %r8, %r8
|
|
jmp 2b
|
|
|
|
.size syscall_handler, .-syscall_handler
|