Revert "microblaze: Simplify syscall rutine"

This reverts commit 0e41c90908881a1b8205c66a66becec7d8d4eb4a.

Break jffs2 rootfs because the patch removes syscall calling
from kernel space.

Signed-off-by: Michal Simek <monstr@monstr.eu>

1 files changed, 39 insertions, 7 deletions

diff --git a/arch/microblaze/kernel/entry.S b/arch/microblaze/kernel/entry.S
index 819238b8a429..41c30cdb2704 100644
--- a/arch/microblaze/kernel/entry.S
+++ b/arch/microblaze/kernel/entry.S
@@ -287,25 +287,44 @@
  * are masked. This is nice, means we don't have to CLI before state save
  */
 C_ENTRY(_user_exception):
-        addi    r14, r14, 4     /* return address is 4 byte after call */
         swi     r1, r0, TOPHYS(PER_CPU(ENTRY_SP)) /* save stack */
+        addi    r14, r14, 4     /* return address is 4 byte after call */
+
+        mfs     r1, rmsr
+        nop
+        andi    r1, r1, MSR_UMS
+        bnei    r1, 1f
+
+/* Kernel-mode state save - kernel execve */
+        lwi     r1, r0, TOPHYS(PER_CPU(ENTRY_SP)); /* Reload kernel stack-ptr*/
+        tophys(r1,r1);
+
+        addik   r1, r1, -STATE_SAVE_SIZE; /* Make room on the stack. */
+        SAVE_REGS
 
+        swi     r1, r1, PTO + PT_MODE; /* pt_regs -> kernel mode */
+        brid    2f;
+        nop;                            /* Fill delay slot */
+
+/* User-mode state save.  */
+1:
         lwi     r1, r0, TOPHYS(PER_CPU(CURRENT_SAVE)); /* get saved current */
         tophys(r1,r1);
         lwi     r1, r1, TS_THREAD_INFO; /* get stack from task_struct */
-        /* MS these three instructions can be added to one */
-        /* addik        r1, r1, THREAD_SIZE; */
-        /* tophys(r1,r1); */
-        /* addik        r1, r1, -STATE_SAVE_SIZE; */
-        addik r1, r1, THREAD_SIZE + CONFIG_KERNEL_BASE_ADDR - CONFIG_KERNEL_START - STATE_SAVE_SIZE;
+/* calculate kernel stack pointer from task struct 8k */
+        addik   r1, r1, THREAD_SIZE;
+        tophys(r1,r1);
+
+        addik   r1, r1, -STATE_SAVE_SIZE; /* Make room on the stack.  */
         SAVE_REGS
         swi     r0, r1, PTO + PT_R3
         swi     r0, r1, PTO + PT_R4
 
+        swi     r0, r1, PTO + PT_MODE;                  /* Was in user-mode. */
         lwi     r11, r0, TOPHYS(PER_CPU(ENTRY_SP));
         swi     r11, r1, PTO+PT_R1;             /* Store user SP.  */
         clear_ums;
-        lwi     CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));
+2:      lwi     CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));
         /* Save away the syscall number.  */
         swi     r12, r1, PTO+PT_R0;
         tovirt(r1,r1)
@@ -375,6 +394,9 @@ C_ENTRY(ret_from_trap):
         swi     r3, r1, PTO + PT_R3
         swi     r4, r1, PTO + PT_R4
 
+        lwi     r11, r1, PTO + PT_MODE;
+/* See if returning to kernel mode, if so, skip resched &c.  */
+        bnei    r11, 2f;
         /* We're returning to user mode, so check for various conditions that
          * trigger rescheduling. */
         /* FIXME: Restructure all these flag checks. */
@@ -417,6 +439,16 @@ C_ENTRY(ret_from_trap):
         RESTORE_REGS;
         addik   r1, r1, STATE_SAVE_SIZE         /* Clean up stack space.  */
         lwi     r1, r1, PT_R1 - PT_SIZE;/* Restore user stack pointer. */
+        bri     6f;
+
+/* Return to kernel state.  */
+2:      set_bip;                        /*  Ints masked for state restore */
+        VM_OFF;
+        tophys(r1,r1);
+        RESTORE_REGS;
+        addik   r1, r1, STATE_SAVE_SIZE         /* Clean up stack space.  */
+        tovirt(r1,r1);
+6:
 TRAP_return:            /* Make global symbol for debugging */
         rtbd    r14, 0; /* Instructions to return from an IRQ */
         nop;