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Removed bits from kernel where pager utcb is set.

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Pagers now set their own utcb explicitly via exchange_registers.
exregs accepts calls from active pagers for this purpose only.
This commit is contained in:
Bahadir Balban
2009-10-18 15:01:38 +03:00
parent 7ba7a2e796
commit 2bd3266498
11 changed files with 79 additions and 58 deletions
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68
src/api/syscall.c
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@@ -10,6 +10,8 @@
#include <l4/generic/resource.h>
#include <l4/generic/tcb.h>
#include <l4/generic/space.h>
#include <l4/generic/capability.h>
#include <l4/generic/container.h>
#include <l4/api/space.h>
#include <l4/api/ipc.h>
#include <l4/api/kip.h>
@@ -33,6 +35,8 @@ void do_exchange_registers(struct ktcb *task, struct exregs_data *exregs)
{
task_context_t *context = &task->context;
if (!exregs->valid_vect)
goto flags;
/*
* NOTE:
* We don't care if register values point at invalid addresses
@@ -74,29 +78,48 @@ void do_exchange_registers(struct ktcb *task, struct exregs_data *exregs)
if (exregs->valid_vect & FIELD_TO_BIT(exregs_context_t, pc))
context->pc = exregs->context.pc;
flags:
/* Set thread's pager if one is supplied */
if (exregs->flags & EXREGS_SET_PAGER)
task->pagerid = exregs->pagerid;
/* Set thread's utcb if supplied */
if (exregs->flags & EXREGS_SET_UTCB)
if (exregs->flags & EXREGS_SET_UTCB) {
task->utcb_address = exregs->utcb_address;
/*
* If task is the one currently runnable,
* update kip utcb reference
*/
if (task == current)
task_update_utcb(task);
}
}
/*
* exchange_registers()
*
* This call is used by the pagers to set (and in the future read)
* the register context of a thread. The thread's registers can be
* set only when the thread is in user mode. A newly created thread
* that is the copy of another thread (forked or cloned) will also
* be given its user mode context on the first chance to execute so
* such threads can also be modified by this call before execution.
* the register context of a thread. The thread's registers that are
* set by this call are loaded whenever the thread gets a chance to
* run in user mode.
*
* It is ensured that whenever this call is made, the thread is
* either already running in user mode, or has been suspended in
* kernel mode, just before returning to user mode.
*
* A newly created thread that is the copy of another thread (forked
* or cloned) will also be given its user mode context on the first
* chance to execute so such threads can also be modified by this
* call before execution.
*
* A thread executing in the kernel cannot be modified since this
* would compromise the kernel. Also the thread must be in suspended
* condition so that the scheduler does not execute it as we modify
* its context.
*
* FIXME: Still looks like suspended threads in the kernel
* need to be made immutable. see src/glue/arm/systable.c
*/
int sys_exchange_registers(struct exregs_data *exregs, l4id_t tid)
{
@@ -114,30 +137,27 @@ int sys_exchange_registers(struct exregs_data *exregs, l4id_t tid)
if (!mutex_trylock(&task->thread_control_lock))
return -EAGAIN;
/* Now check that the task is suspended */
if (task->state != TASK_INACTIVE) {
/*
* Now check that the task is suspended.
*
* Only modification of non-register fields are
* allowed on active tasks and those tasks must
* be the pagers making the call on themselves.
*/
if (task->state != TASK_INACTIVE && exregs->valid_vect &&
current != task && task->pager->tcb != current) {
err = -EACTIVE;
goto out;
}
#if 0
A suspended thread implies it cannot do any harm
even if it is in kernel mode.
/*
* The thread must be in user mode for its context
* to be modified.
* FIXME:
* Capability Check.
* Whose clist are we ought to check? Pager's or threads?
* Need to check exregs capability
* Need to check utcb capability if present.
* if ((exregs->flags & EXREGS_SET_UTCB) &&
*/
if (!TASK_IN_USER(task)) {
err = -EPERM;
goto out;
}
#endif
/* Check UTCB is in valid range */
if (exregs->flags & EXREGS_SET_UTCB &&
!(exregs->utcb_address >= UTCB_AREA_START &&
exregs->utcb_address < UTCB_AREA_END))
return -EINVAL;
/* Copy registers */
do_exchange_registers(task, exregs);