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authorJonas Bonn <jonas@southpole.se>2012-10-19 18:07:44 +0200
committerJonas Bonn <jonas@southpole.se>2012-10-19 18:32:36 +0200
commitcbf23cf1b96819599f6a1b9658d1bf3a97c6ff15 (patch)
tree4ed2583ded570499617cc6fd9caffb4f17eddbd5 /arch/openrisc/kernel
parent287ad220cd8b5a9d29f71c78f6e4051093f051fc (diff)
downloadlinux-cbf23cf1b96819599f6a1b9658d1bf3a97c6ff15.tar.gz
openrisc: use generic kernel_thread/kernel_execve
Signed-off-by: Jonas Bonn <jonas@southpole.se>
Diffstat (limited to 'arch/openrisc/kernel')
-rw-r--r--arch/openrisc/kernel/entry.S30
-rw-r--r--arch/openrisc/kernel/process.c138
2 files changed, 66 insertions, 102 deletions
diff --git a/arch/openrisc/kernel/entry.S b/arch/openrisc/kernel/entry.S
index 374e63e7c9f..dce86aef8ab 100644
--- a/arch/openrisc/kernel/entry.S
+++ b/arch/openrisc/kernel/entry.S
@@ -894,6 +894,16 @@ ENTRY(ret_from_fork)
l.jal schedule_tail
l.nop
+ /* Check if we are a kernel thread */
+ l.sfeqi r20,0
+ l.bf 1f
+ l.nop
+
+ /* ...we are a kernel thread so invoke the requested callback */
+ l.jalr r20
+ l.or r3,r22,r0
+
+1:
/* _syscall_returns expect r11 to contain return value */
l.lwz r11,PT_GPR11(r1)
@@ -915,26 +925,6 @@ ENTRY(ret_from_fork)
l.j _syscall_return
l.nop
-/* Since syscalls don't save call-clobbered registers, the args to
- * kernel_thread_helper will need to be passed through callee-saved
- * registers and copied to the parameter registers when the thread
- * begins running.
- *
- * See arch/openrisc/kernel/process.c:
- * The args are passed as follows:
- * arg1 (r3) : passed in r20
- * arg2 (r4) : passed in r22
- */
-
-ENTRY(_kernel_thread_helper)
- l.or r3,r20,r0
- l.or r4,r22,r0
- l.movhi r31,hi(kernel_thread_helper)
- l.ori r31,r31,lo(kernel_thread_helper)
- l.jr r31
- l.nop
-
-
/* ========================================================[ switch ] === */
/*
diff --git a/arch/openrisc/kernel/process.c b/arch/openrisc/kernel/process.c
index ad26d5af264..a0f467e438f 100644
--- a/arch/openrisc/kernel/process.c
+++ b/arch/openrisc/kernel/process.c
@@ -109,65 +109,82 @@ void release_thread(struct task_struct *dead_task)
*/
extern asmlinkage void ret_from_fork(void);
+/*
+ * copy_thread
+ * @clone_flags: flags
+ * @usp: user stack pointer or fn for kernel thread
+ * @arg: arg to fn for kernel thread; always NULL for userspace thread
+ * @p: the newly created task
+ * @regs: CPU context to copy for userspace thread; always NULL for kthread
+ *
+ * At the top of a newly initialized kernel stack are two stacked pt_reg
+ * structures. The first (topmost) is the userspace context of the thread.
+ * The second is the kernelspace context of the thread.
+ *
+ * A kernel thread will not be returning to userspace, so the topmost pt_regs
+ * struct can be uninitialized; it _does_ need to exist, though, because
+ * a kernel thread can become a userspace thread by doing a kernel_execve, in
+ * which case the topmost context will be initialized and used for 'returning'
+ * to userspace.
+ *
+ * The second pt_reg struct needs to be initialized to 'return' to
+ * ret_from_fork. A kernel thread will need to set r20 to the address of
+ * a function to call into (with arg in r22); userspace threads need to set
+ * r20 to NULL in which case ret_from_fork will just continue a return to
+ * userspace.
+ *
+ * A kernel thread 'fn' may return; this is effectively what happens when
+ * kernel_execve is called. In that case, the userspace pt_regs must have
+ * been initialized (which kernel_execve takes care of, see start_thread
+ * below); ret_from_fork will then continue its execution causing the
+ * 'kernel thread' to return to userspace as a userspace thread.
+ */
+
int
copy_thread(unsigned long clone_flags, unsigned long usp,
- unsigned long unused, struct task_struct *p, struct pt_regs *regs)
+ unsigned long arg, struct task_struct *p, struct pt_regs *regs)
{
- struct pt_regs *childregs;
+ struct pt_regs *userregs;
struct pt_regs *kregs;
unsigned long sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
- struct thread_info *ti;
unsigned long top_of_kernel_stack;
top_of_kernel_stack = sp;
p->set_child_tid = p->clear_child_tid = NULL;
- /* Copy registers */
- /* redzone */
- sp -= STACK_FRAME_OVERHEAD;
+ /* Locate userspace context on stack... */
+ sp -= STACK_FRAME_OVERHEAD; /* redzone */
sp -= sizeof(struct pt_regs);
- childregs = (struct pt_regs *)sp;
+ userregs = (struct pt_regs *) sp;
- /* Copy parent registers */
- *childregs = *regs;
+ /* ...and kernel context */
+ sp -= STACK_FRAME_OVERHEAD; /* redzone */
+ sp -= sizeof(struct pt_regs);
+ kregs = (struct pt_regs *)sp;
- if ((childregs->sr & SPR_SR_SM) == 1) {
- /* for kernel thread, set `current_thread_info'
- * and stackptr in new task
- */
- childregs->sp = (unsigned long)task_stack_page(p) + THREAD_SIZE;
- childregs->gpr[10] = (unsigned long)task_thread_info(p);
+ if (unlikely(p->flags & PF_KTHREAD)) {
+ memset(kregs, 0, sizeof(struct pt_regs));
+ kregs->gpr[20] = usp; /* fn, kernel thread */
+ kregs->gpr[22] = arg;
} else {
- childregs->sp = usp;
- }
-
- childregs->gpr[11] = 0; /* Result from fork() */
+ *userregs = *regs;
- /*
- * The way this works is that at some point in the future
- * some task will call _switch to switch to the new task.
- * That will pop off the stack frame created below and start
- * the new task running at ret_from_fork. The new task will
- * do some house keeping and then return from the fork or clone
- * system call, using the stack frame created above.
- */
- /* redzone */
- sp -= STACK_FRAME_OVERHEAD;
- sp -= sizeof(struct pt_regs);
- kregs = (struct pt_regs *)sp;
+ userregs->sp = usp;
+ userregs->gpr[11] = 0; /* Result from fork() */
- ti = task_thread_info(p);
- ti->ksp = sp;
+ kregs->gpr[20] = 0; /* Userspace thread */
+ }
- /* kregs->sp must store the location of the 'pre-switch' kernel stack
- * pointer... for a newly forked process, this is simply the top of
- * the kernel stack.
+ /*
+ * _switch wants the kernel stack page in pt_regs->sp so that it
+ * can restore it to thread_info->ksp... see _switch for details.
*/
kregs->sp = top_of_kernel_stack;
- kregs->gpr[10] = (unsigned long)task_thread_info(p);
kregs->gpr[9] = (unsigned long)ret_from_fork;
+ task_thread_info(p)->ksp = (unsigned long)kregs;
+
return 0;
}
@@ -176,16 +193,14 @@ copy_thread(unsigned long clone_flags, unsigned long usp,
*/
void start_thread(struct pt_regs *regs, unsigned long pc, unsigned long sp)
{
- unsigned long sr = regs->sr & ~SPR_SR_SM;
+ unsigned long sr = mfspr(SPR_SR) & ~SPR_SR_SM;
set_fs(USER_DS);
- memset(regs->gpr, 0, sizeof(regs->gpr));
+ memset(regs, 0, sizeof(struct pt_regs));
regs->pc = pc;
regs->sr = sr;
regs->sp = sp;
-
-/* printk("start thread, ksp = %lx\n", current_thread_info()->ksp);*/
}
/* Fill in the fpu structure for a core dump. */
@@ -236,31 +251,6 @@ void dump_elf_thread(elf_greg_t *dest, struct pt_regs* regs)
dest[35] = 0;
}
-extern void _kernel_thread_helper(void);
-
-void __noreturn kernel_thread_helper(int (*fn) (void *), void *arg)
-{
- do_exit(fn(arg));
-}
-
-/*
- * Create a kernel thread.
- */
-int kernel_thread(int (*fn) (void *), void *arg, unsigned long flags)
-{
- struct pt_regs regs;
-
- memset(&regs, 0, sizeof(regs));
-
- regs.gpr[20] = (unsigned long)fn;
- regs.gpr[22] = (unsigned long)arg;
- regs.sr = mfspr(SPR_SR);
- regs.pc = (unsigned long)_kernel_thread_helper;
-
- return do_fork(flags | CLONE_VM | CLONE_UNTRACED,
- 0, &regs, 0, NULL, NULL);
-}
-
/*
* sys_execve() executes a new program.
*/
@@ -291,19 +281,3 @@ unsigned long get_wchan(struct task_struct *p)
return 0;
}
-
-int kernel_execve(const char *filename, char *const argv[], char *const envp[])
-{
- register long __res asm("r11") = __NR_execve;
- register long __a asm("r3") = (long)(filename);
- register long __b asm("r4") = (long)(argv);
- register long __c asm("r5") = (long)(envp);
- __asm__ volatile ("l.sys 1"
- : "=r" (__res), "=r"(__a), "=r"(__b), "=r"(__c)
- : "0"(__res), "1"(__a), "2"(__b), "3"(__c)
- : "r6", "r7", "r8", "r12", "r13", "r15",
- "r17", "r19", "r21", "r23", "r25", "r27",
- "r29", "r31");
- __asm__ volatile ("l.nop");
- return __res;
-}