Travis Geiselbrecht
1cbf8f4b3c
The first use is to let the kernel decide what the preferred syscall mechanism is at boot time and copy the appropriate user space code there. Can be used for routines the kernel can decide best how to use (memcpy, some timing routines, etc). git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@20161 a95241bf-73f2-0310-859d-f6bbb57e9c96
75 lines
1.9 KiB
C
75 lines
1.9 KiB
C
/*
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* Copyright 2007, Travis Geiselbrecht. All rights reserved.
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* Distributed under the terms of the MIT License.
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*/
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#include <vm.h>
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#include <arch/x86/commpage.h>
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#include <KernelExport.h>
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#include <string.h>
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#include <os/kernel/arch/x86/commpage.h>
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static area_id comm_area;
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static area_id user_comm_area;
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static unsigned long *comm_ptr;
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static unsigned long *user_comm_ptr;
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static void *next_comm_addr;
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// user syscall assembly stub
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extern void _user_syscall_int(void);
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extern unsigned int _user_syscall_int_end;
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static inline
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addr_t commpage_ptr_to_user_ptr(const void *ptr)
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{
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return ((addr_t)ptr) + ((addr_t)user_comm_ptr - (addr_t)comm_ptr);
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}
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static
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status_t initialize_commpage_syscall(void)
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{
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size_t len;
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// for now, we're hard coded to use the legacy method (int 99)
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len = (size_t)((void *)&_user_syscall_int_end - (void *)&_user_syscall_int);
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memcpy(next_comm_addr, &_user_syscall_int, len);
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// fill in the table entry
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comm_ptr[COMMPAGE_ENTRY_SYSCALL] = commpage_ptr_to_user_ptr(next_comm_addr);
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next_comm_addr = (void *)((addr_t)next_comm_addr + ROUNDUP(len, 4));
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return B_OK;
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}
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status_t
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commpage_init(void)
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{
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int i;
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// create a read/write kernel area
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comm_area = create_area("commpage", (void **)&comm_ptr, B_ANY_ADDRESS, COMMPAGE_SIZE, B_FULL_LOCK,
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B_KERNEL_WRITE_AREA | B_KERNEL_READ_AREA);
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// clone it at a fixed address with user read/only permissions
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user_comm_ptr = (void *)USER_COMMPAGE_ADDR;
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user_comm_area = clone_area("user_commpage", (void **)&user_comm_ptr, B_EXACT_ADDRESS,
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B_READ_AREA | B_EXECUTE_AREA, comm_area);
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// zero it out
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memset(comm_ptr, 0, COMMPAGE_SIZE);
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// fill in some of the table
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comm_ptr[0] = COMMPAGE_SIGNATURE;
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comm_ptr[1] = COMMPAGE_VERSION;
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// the next slot to allocate space is after the table
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next_comm_addr = (void *)&comm_ptr[TABLE_ENTRIES];
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// select the optimum syscall mechanism and patch the commpage
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initialize_commpage_syscall();
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return B_OK;
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}
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