Merge commit '5bc66170dc486556a1e36fd384463536573f4b82' into x86/urgent

From Borislav Petkov <bp@amd64.org>:

Below is a RAS fix which reverts the addition of a sysfs attribute
which we agreed is not needed, post-factum. And this should go in now
because that sysfs attribute is going to end up in 3.7 otherwise and
thus exposed to userspace; removing it then would be a lot harder.

This is done as a merge rather than a simple patch/cherry-pick since
the baseline for this patch was not in the previous x86/urgent.

Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

1 files changed, 14 insertions, 29 deletions

diff --git a/arch/um/kernel/process.c b/arch/um/kernel/process.c
index 57fc7028714..b6d699cdd55 100644
--- a/arch/um/kernel/process.c
+++ b/arch/um/kernel/process.c
@@ -23,10 +23,10 @@
 #include <asm/pgtable.h>
 #include <asm/mmu_context.h>
 #include <asm/uaccess.h>
-#include "as-layout.h"
-#include "kern_util.h"
-#include "os.h"
-#include "skas.h"
+#include <as-layout.h>
+#include <kern_util.h>
+#include <os.h>
+#include <skas.h>
 
 /*
  * This is a per-cpu array.  A processor only modifies its entry and it only
@@ -69,18 +69,6 @@ unsigned long alloc_stack(int order, int atomic)
 	return page;
 }
 
-int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
-{
-	int pid;
-
-	current->thread.request.u.thread.proc = fn;
-	current->thread.request.u.thread.arg = arg;
-	pid = do_fork(CLONE_VM | CLONE_UNTRACED | flags, 0,
-		      &current->thread.regs, 0, NULL, NULL);
-	return pid;
-}
-EXPORT_SYMBOL(kernel_thread);
-
 static inline void set_current(struct task_struct *task)
 {
 	cpu_tasks[task_thread_info(task)->cpu] = ((struct cpu_task)
@@ -147,14 +135,10 @@ void new_thread_handler(void)
 	arg = current->thread.request.u.thread.arg;
 
 	/*
-	 * The return value is 1 if the kernel thread execs a process,
-	 * 0 if it just exits
+	 * callback returns only if the kernel thread execs a process
 	 */
-	n = run_kernel_thread(fn, arg, &current->thread.exec_buf);
-	if (n == 1)
-		userspace(&current->thread.regs.regs);
-	else
-		do_exit(0);
+	n = fn(arg);
+	userspace(&current->thread.regs.regs);
 }
 
 /* Called magically, see new_thread_handler above */
@@ -177,15 +161,16 @@ void fork_handler(void)
 }
 
 int copy_thread(unsigned long clone_flags, unsigned long sp,
-		unsigned long stack_top, struct task_struct * p,
+		unsigned long arg, struct task_struct * p,
 		struct pt_regs *regs)
 {
 	void (*handler)(void);
+	int kthread = current->flags & PF_KTHREAD;
 	int ret = 0;
 
 	p->thread = (struct thread_struct) INIT_THREAD;
 
-	if (current->thread.forking) {
+	if (!kthread) {
 	  	memcpy(&p->thread.regs.regs, &regs->regs,
 		       sizeof(p->thread.regs.regs));
 		PT_REGS_SET_SYSCALL_RETURN(&p->thread.regs, 0);
@@ -195,16 +180,16 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
 		handler = fork_handler;
 
 		arch_copy_thread(&current->thread.arch, &p->thread.arch);
-	}
-	else {
+	} else {
 		get_safe_registers(p->thread.regs.regs.gp, p->thread.regs.regs.fp);
-		p->thread.request.u.thread = current->thread.request.u.thread;
+		p->thread.request.u.thread.proc = (int (*)(void *))sp;
+		p->thread.request.u.thread.arg = (void *)arg;
 		handler = new_thread_handler;
 	}
 
 	new_thread(task_stack_page(p), &p->thread.switch_buf, handler);
 
-	if (current->thread.forking) {
+	if (!kthread) {
 		clear_flushed_tls(p);
 
 		/*