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Saving all registers in syscall so that return from fork is easier.

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Child needs rewound function stack in order to reach registers r9-r12
that have original userspace values. But we jump to return_from_syscall
without rewinding the stack. Therefore to ease context restore, we save
r9-r12 on the stack as well upon syscall entry.
This commit is contained in:
Bahadir Balban
2008-09-01 16:19:03 +03:00
parent 021bd6bc99
commit afc0599d49
3 changed files with 28 additions and 12 deletions
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19
src/api/thread.c
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@@ -106,17 +106,17 @@ int arch_setup_new_thread(struct ktcb *new, struct ktcb *orig)
* A cleaner but slower way would be the pager setting child registers
* via exchanges_registers() and start the child thread afterwards.
*/
new->syscall_regs->r0 = 0;
KTCB_REF_MR0(new)[MR_RETURN] = 0;
/*
* Set up the stack pointer, saved program status register and program
* counter so that next time the new thread schedules, it executes the
* end part of the system call exception where the previous context is
* restored.
* Set up the stack pointer, saved program status register and the
* program counter so that next time the new thread schedules, it
* executes the end part of the system call exception where the
* previous context is restored.
*/
new->context.sp = (unsigned long)new->syscall_regs;
new->context.pc = (unsigned long)&return_from_syscall;
new->context.spsr = (unsigned long)orig->context.spsr;
new->context.spsr = (unsigned long)orig->context.spsr;
/* Copy other relevant fields from original ktcb */
new->pagerid = orig->pagerid;
@@ -139,6 +139,7 @@ int thread_create(struct task_ids *ids, unsigned int flags)
{
struct ktcb *task, *new = (struct ktcb *)zalloc_page();
flags &= THREAD_FLAGS_MASK;
int ret = 0;
if (flags == THREAD_CREATE_NEWSPC) {
/* Allocate new pgd and copy all kernel areas */
@@ -192,13 +193,15 @@ out:
* system call return environment so that it can safely
* return as a copy of its original thread.
*/
if (flags == THREAD_CREATE_COPYSPC)
if (flags == THREAD_CREATE_COPYSPC) {
arch_setup_new_thread(new, task);
ret = new->tid;
}
/* Add task to global hlist of tasks */
add_task_global(new);
return 0;
return ret;
}
/*