m68k: sanitize copy_thread(), fork/vfork/clone wrappers, switch to generic fork/vfork

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 44 insertions, 71 deletions

diff --git a/arch/m68k/kernel/entry.S b/arch/m68k/kernel/entry.S
index 45b2f293f8c..a78f5649e8d 100644
--- a/arch/m68k/kernel/entry.S
+++ b/arch/m68k/kernel/entry.S
@@ -44,34 +44,29 @@
 
 .globl system_call, buserr, trap, resume
 .globl sys_call_table
-.globl sys_fork, sys_clone, sys_vfork
+.globl __sys_fork, __sys_clone, __sys_vfork
 .globl ret_from_interrupt, bad_interrupt
 .globl auto_irqhandler_fixup
 .globl user_irqvec_fixup
 
 .text
-ENTRY(sys_fork)
+ENTRY(__sys_fork)
         SAVE_SWITCH_STACK
-        pea     %sp@(SWITCH_STACK_SIZE)
-        jbsr    m68k_fork
-        addql   #4,%sp
-        RESTORE_SWITCH_STACK
+        jbsr    sys_fork
+        lea     %sp@(24),%sp
         rts
 
-ENTRY(sys_clone)
+ENTRY(__sys_clone)
         SAVE_SWITCH_STACK
         pea     %sp@(SWITCH_STACK_SIZE)
         jbsr    m68k_clone
-        addql   #4,%sp
-        RESTORE_SWITCH_STACK
+        lea     %sp@(28),%sp
         rts
 
-ENTRY(sys_vfork)
+ENTRY(__sys_vfork)
         SAVE_SWITCH_STACK
-        pea     %sp@(SWITCH_STACK_SIZE)
-        jbsr    m68k_vfork
-        addql   #4,%sp
-        RESTORE_SWITCH_STACK
+        jbsr    sys_vfork
+        lea     %sp@(24),%sp
         rts
 
 ENTRY(sys_sigreturn)
diff --git a/arch/m68k/kernel/process.c b/arch/m68k/kernel/process.c
index c51bb172e14..aa9b1100027 100644
--- a/arch/m68k/kernel/process.c
+++ b/arch/m68k/kernel/process.c
@@ -136,57 +136,36 @@ void flush_thread(void)
 }
 
 /*
- * "m68k_fork()".. By the time we get here, the
- * non-volatile registers have also been saved on the
- * stack. We do some ugly pointer stuff here.. (see
- * also copy_thread)
+ * Why not generic sys_clone, you ask?  m68k passes all arguments on stack.
+ * And we need all registers saved, which means a bunch of stuff pushed
+ * on top of pt_regs, which means that sys_clone() arguments would be
+ * buried.  We could, of course, copy them, but it's too costly for no
+ * good reason - generic clone() would have to copy them *again* for
+ * do_fork() anyway.  So in this case it's actually better to pass pt_regs *
+ * and extract arguments for do_fork() from there.  Eventually we might
+ * go for calling do_fork() directly from the wrapper, but only after we
+ * are finished with do_fork() prototype conversion.
  */
-
-asmlinkage int m68k_fork(struct pt_regs *regs)
-{
-#ifdef CONFIG_MMU
-        return do_fork(SIGCHLD, rdusp(), regs, 0, NULL, NULL);
-#else
-        return -EINVAL;
-#endif
-}
-
-asmlinkage int m68k_vfork(struct pt_regs *regs)
-{
-        return do_fork(CLONE_VFORK | CLONE_VM | SIGCHLD, rdusp(), regs, 0,
-                       NULL, NULL);
-}
-
 asmlinkage int m68k_clone(struct pt_regs *regs)
 {
-        unsigned long clone_flags;
-        unsigned long newsp;
-        int __user *parent_tidptr, *child_tidptr;
-
-        /* syscall2 puts clone_flags in d1 and usp in d2 */
-        clone_flags = regs->d1;
-        newsp = regs->d2;
-        parent_tidptr = (int __user *)regs->d3;
-        child_tidptr = (int __user *)regs->d4;
-        if (!newsp)
-                newsp = rdusp();
-        return do_fork(clone_flags, newsp, regs, 0,
-                       parent_tidptr, child_tidptr);
+        /* regs will be equal to current_pt_regs() */
+        return do_fork(regs->d1, regs->d2, regs, 0,
+                       (int __user *)regs->d3, (int __user *)regs->d4);
 }
 
 int copy_thread(unsigned long clone_flags, unsigned long usp,
                  unsigned long arg,
-                 struct task_struct * p, struct pt_regs * regs)
+                 struct task_struct * p, struct pt_regs * unused)
 {
-        struct pt_regs * childregs;
-        struct switch_stack *childstack;
+        struct fork_frame {
+                struct switch_stack sw;
+                struct pt_regs regs;
+        } *frame;
 
-        childregs = (struct pt_regs *) (task_stack_page(p) + THREAD_SIZE) - 1;
-        childstack = ((struct switch_stack *) childregs) - 1;
+        frame = (struct fork_frame *) (task_stack_page(p) + THREAD_SIZE) - 1;
 
-        p->thread.usp = usp;
-        p->thread.ksp = (unsigned long)childstack;
-        p->thread.esp0 = (unsigned long)childregs;
+        p->thread.ksp = (unsigned long)frame;
+        p->thread.esp0 = (unsigned long)&frame->regs;
 
         /*
          * Must save the current SFC/DFC value, NOT the value when
@@ -194,25 +173,24 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
          */
         p->thread.fs = get_fs().seg;
 
-        if (unlikely(!regs)) {
+        if (unlikely(p->flags & PF_KTHREAD)) {
                 /* kernel thread */
-                memset(childstack, 0,
-                        sizeof(struct switch_stack) + sizeof(struct pt_regs));
-                childregs->sr = PS_S;
-                childstack->a3 = usp; /* function */
-                childstack->d7 = arg;
-                childstack->retpc = (unsigned long)ret_from_kernel_thread;
+                memset(frame, 0, sizeof(struct fork_frame));
+                frame->regs.sr = PS_S;
+                frame->sw.a3 = usp; /* function */
+                frame->sw.d7 = arg;
+                frame->sw.retpc = (unsigned long)ret_from_kernel_thread;
                 p->thread.usp = 0;
                 return 0;
         }
-        *childregs = *regs;
-        childregs->d0 = 0;
-
-        *childstack = ((struct switch_stack *) regs)[-1];
-        childstack->retpc = (unsigned long)ret_from_fork;
+        memcpy(frame, container_of(current_pt_regs(), struct fork_frame, regs),
+                sizeof(struct fork_frame));
+        frame->regs.d0 = 0;
+        frame->sw.retpc = (unsigned long)ret_from_fork;
+        p->thread.usp = usp ?: rdusp();
 
         if (clone_flags & CLONE_SETTLS)
-                task_thread_info(p)->tp_value = regs->d5;
+                task_thread_info(p)->tp_value = frame->regs.d5;
 
 #ifdef CONFIG_FPU
         if (!FPU_IS_EMU) {
diff --git a/arch/m68k/kernel/syscalltable.S b/arch/m68k/kernel/syscalltable.S
index 4fc2e29b771..c30da5b3f2d 100644
--- a/arch/m68k/kernel/syscalltable.S
+++ b/arch/m68k/kernel/syscalltable.S
@@ -22,7 +22,7 @@ ALIGN
 ENTRY(sys_call_table)
         .long sys_restart_syscall       /* 0 - old "setup()" system call, used for restarting */
         .long sys_exit
-        .long sys_fork
+        .long __sys_fork
         .long sys_read
         .long sys_write
         .long sys_open                  /* 5 */
@@ -140,7 +140,7 @@ ENTRY(sys_call_table)
         .long sys_ipc
         .long sys_fsync
         .long sys_sigreturn
-        .long sys_clone                 /* 120 */
+        .long __sys_clone               /* 120 */
         .long sys_setdomainname
         .long sys_newuname
         .long sys_cacheflush            /* modify_ldt for i386 */
@@ -210,7 +210,7 @@ ENTRY(sys_call_table)
         .long sys_sendfile