87 lines
2.6 KiB
C
87 lines
2.6 KiB
C
/* The system call implemented in this file:
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* m_type: SYS_PHYS2SEG
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*
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* The parameters for this system call are:
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* m4_l1: SEG_SELECT (return segment selector here)
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* m4_l2: SEG_OFFSET (return offset within segment here)
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* m4_l3: SEG_PHYS (physical address to convert)
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* m4_l4: SEG_SIZE (size of segment)
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*
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* Author:
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* Jorrit N. Herder <jnherder@cs.vu.nl>
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*/
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#include "../kernel.h"
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#include "../system.h"
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#include "../protect.h"
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/*===========================================================================*
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* do_phys2seg *
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*===========================================================================*/
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PUBLIC int do_phys2seg(m_ptr)
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register message *m_ptr; /* pointer to request message */
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{
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/* Return a segment selector and offset that can be used to reach a physical
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* address, for use by a driver doing memory I/O in the A0000 - DFFFF range.
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*/
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u16_t selector;
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vir_bytes offset;
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register struct proc *rp;
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phys_bytes phys = (phys_bytes) m_ptr->SEG_PHYS;
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vir_bytes size = (vir_bytes) m_ptr->SEG_SIZE;
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int result;
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#if 0
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kprintf("FLAT DS SELECTOR used\n", NO_ARG);
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selector = FLAT_DS_SELECTOR;
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offset = phys;
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#else
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kprintf("Using Experimental LDT selector for video memory\n", NO_ARG);
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if (!protected_mode) {
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selector = phys / HCLICK_SIZE;
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offset = phys % HCLICK_SIZE;
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result = OK;
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} else {
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/* Check if the segment size can be recorded in bytes, that is, check
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* if descriptor's limit field can delimited the allowed memory region
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* precisely. This works up to 1MB. If the size is larger, 4K pages
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* instead of bytes are used.
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*/
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if (size < BYTE_GRAN_MAX) {
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rp = proc_addr(m_ptr->m_source);
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init_dataseg(&rp->p_ldt[EXTRA_LDT_INDEX], phys, size,
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USER_PRIVILEGE);
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selector = (EXTRA_LDT_INDEX * 0x08) | (1 * 0x04) | USER_PRIVILEGE;
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offset = 0;
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result = OK;
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} else {
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#if ENABLE_USERPRIV && ENABLE_LOOSELDT
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rp = proc_addr(m_ptr->m_source);
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init_dataseg(&rp->p_ldt[EXTRA_LDT_INDEX], phys & ~0xFFFF, 0,
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USER_PRIVILEGE);
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selector = (EXTRA_LDT_INDEX * 0x08) | (1 * 0x04) | USER_PRIVILEGE;
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offset = phys & 0xFFFF;
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result = OK;
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#else
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result = E2BIG; /* allow settings only */
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#endif
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}
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}
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#endif
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#if 0
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kprintf("do_phys2seg: proc %d", m_ptr->m_source);
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kprintf(" phys %u", phys);
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kprintf(" size %u", size);
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kprintf(" sel %u", selector);
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kprintf(" off %u\n", offset);
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#endif
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m_ptr->SEG_SELECT = selector;
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m_ptr->SEG_OFFSET = offset;
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return(result);
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}
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