minix/kernel/system/do_segctl.c
Tomas Hruby cca24d06d8 This patch removes the global variables who_p and who_e from the
kernel (sys task).  The main reason is that these would have to become
cpu local variables on SMP.  Once the system task is not a task but a
genuine part of the kernel there is even less reason to have these
extra variables as proc_ptr will already contain all neccessary
information. In addition converting who_e to the process pointer and
back again all the time will be avoided.

Although proc_ptr will contain all important information, accessing it
as a cpu local variable will be fairly expensive, hence the value
would be assigned to some on stack local variable. Therefore it is
better to add the 'caller' argument to the syscall handlers to pass
the value on stack anyway. It also clearly denotes on who's behalf is
the syscall being executed.

This patch also ANSIfies the syscall function headers.

Last but not least, it also fixes a potential bug in virtual_copy_f()
in case the check is disabled. So far the function in case of a
failure could possible reuse an old who_p in case this function had
not been called from the system task.

virtual_copy_f() takes the caller as a parameter too. In case the
checking is disabled, the caller must be NULL and non NULL if it is
enabled as we must be able to suspend the caller.
2010-02-03 09:04:48 +00:00

55 lines
1.7 KiB
C

/* The kernel call implemented in this file:
* m_type: SYS_SEGCTL
*
* The parameters for this kernel call are:
* m4_l3: SEG_PHYS (physical base address)
* m4_l4: SEG_SIZE (size of segment)
* m4_l1: SEG_SELECT (return segment selector here)
* m4_l2: SEG_OFFSET (return offset within segment here)
* m4_l5: SEG_INDEX (return index into remote memory map here)
*/
#include "../system.h"
#if USE_SEGCTL
/*===========================================================================*
* do_segctl *
*===========================================================================*/
PUBLIC int do_segctl(struct proc * caller, message * m_ptr)
{
/* Return a segment selector and offset that can be used to reach a physical
* address, for use by a driver doing memory I/O in the A0000 - DFFFF range.
*/
u32_t selector;
vir_bytes offset;
int i, index;
phys_bytes phys = (phys_bytes) m_ptr->SEG_PHYS;
vir_bytes size = (vir_bytes) m_ptr->SEG_SIZE;
int result;
/* First check if there is a slot available for this segment. */
index = -1;
for (i=0; i < NR_REMOTE_SEGS; i++) {
if (! caller->p_priv->s_farmem[i].in_use) {
index = i;
caller->p_priv->s_farmem[i].in_use = TRUE;
caller->p_priv->s_farmem[i].mem_phys = phys;
caller->p_priv->s_farmem[i].mem_len = size;
break;
}
}
if (index < 0) return(ENOSPC);
offset = alloc_remote_segment(&selector, &caller->p_seg,
i, phys, size, USER_PRIVILEGE);
result = OK;
/* Request successfully done. Now return the result. */
m_ptr->SEG_INDEX = index | REMOTE_SEG;
m_ptr->SEG_SELECT = selector;
m_ptr->SEG_OFFSET = offset;
return(result);
}
#endif /* USE_SEGCTL */