Changes in kernel/arch/mips32/src/start.S [0cb47cf:96e0748d] in mainline

File:

• kernel/arch/mips32/src/start.S (modified) (12 diffs)

kernel/arch/mips32/src/start.S

@@ -45 +45 @@
 .global userspace_asm
 
-/*
- * Which status bits should are thread-local:
- * KSU(UM), EXL, ERL, IE
- */
-#define REG_SAVE_MASK 0x1f
-
-/*
- * Save registers to space defined by \r
- * We will change status: Disable ERL, EXL, UM, IE
- * These changes will be automatically reversed in REGISTER_LOAD
- * %sp is NOT saved as part of these registers
- */
+# Which status bits should are thread-local
+#define REG_SAVE_MASK 0x1f # KSU(UM), EXL, ERL, IE
+        
+# Save registers to space defined by \r
+# We will change status: Disable ERL,EXL,UM,IE
+# These changes will be automatically reversed in REGISTER_LOAD
+# SP is NOT saved as part of these registers
 .macro REGISTERS_STORE_AND_EXC_RESET r
         sw $at, EOFFSET_AT(\r)
@@ -75 +70 @@
         sw $t8, EOFFSET_T8(\r)
         sw $t9, EOFFSET_T9(\r)
-        
+
         mflo $at
         sw $at, EOFFSET_LO(\r)
@@ -84 +79 @@
         sw $ra, EOFFSET_RA(\r)
         sw $k1, EOFFSET_K1(\r)
-        
+
         mfc0 $t0, $status
         mfc0 $t1, $epc
         
-        /* save only KSU, EXL, ERL, IE */
-        and $t2, $t0, REG_SAVE_MASK
-        
-        /* clear KSU, EXL, ERL, IE */
-        li $t3, ~(REG_SAVE_MASK)
-        and $t0, $t0, $t3
-        
-        sw $t2, EOFFSET_STATUS(\r)
-        sw $t1, EOFFSET_EPC(\r)
+        and $t2, $t0, REG_SAVE_MASK     # Save only KSU,EXL,ERL,IE
+        li $t3, ~(0x1f)
+        and $t0, $t0, $t3               # Clear KSU,EXL,ERL,IE
+        
+        sw $t2,EOFFSET_STATUS(\r)
+        sw $t1,EOFFSET_EPC(\r)
         mtc0 $t0, $status
 .endm
 
 .macro REGISTERS_LOAD r
-        /*
-         * Update only UM, EXR, IE from status, the rest
-         * is controlled by OS and not bound to task.
-         */
+        # Update only UM,EXR,IE from status, the rest
+        # is controlled by OS and not bound to task
         mfc0 $t0, $status
         lw $t1,EOFFSET_STATUS(\r)
-        
-        /* mask UM, EXL, ERL, IE */
-        li $t2, ~REG_SAVE_MASK
+
+        li $t2, ~REG_SAVE_MASK          # Mask UM,EXL,ERL,IE
         and $t0, $t0, $t2
         
-        /* copy UM, EXL, ERL, IE from saved status */
-        or $t0, $t0, $t1
+        or $t0, $t0, $t1                # Copy UM,EXL, ERL, IE from saved status
         mtc0 $t0, $status
         
@@ -141 +129 @@
         lw $at, EOFFSET_HI(\r)
         mthi $at
-        
+
         lw $at, EOFFSET_EPC(\r)
         mtc0 $at, $epc
@@ -149 +137 @@
 .endm
 
-/*
- * Move kernel stack pointer address to register $k0.
- * If we are in user mode, load the appropriate stack address.
- */
+# Move kernel stack pointer address to register K0
+# - if we are in user mode, load the appropriate stack
+# address
 .macro KERNEL_STACK_TO_K0
-        /* if we are in user mode */
+        # If we are in user mode
         mfc0 $k0, $status
         andi $k0, 0x10
@@ -161 +148 @@
         add $k0, $sp, 0
         
-        /* move $k0 pointer to kernel stack */
+        # Move $k0 pointer to kernel stack
         lui $k0, %hi(supervisor_sp)
         ori $k0, $k0, %lo(supervisor_sp)
-        
-        /* move $k0 (supervisor_sp) */
+        # Move $k0 (superveisor_sp)
         lw $k0, 0($k0)
-        
-        1:
+1:
 .endm
 
 .org 0x0
 kernel_image_start:
-        /* load temporary stack */
+        /* Load temporary stack */
         lui $sp, %hi(end_stack)
         ori $sp, $sp, %lo(end_stack)
         
-        /* not sure about this, but might be needed for PIC code */
+        /* Not sure about this, but might
+           be needed for PIC code */
         lui $gp, 0x8000
         
         /* $a1 contains physical address of bootinfo_t */
+        
         jal arch_pre_main
         nop
@@ -187 +174 @@
         nop
 
-.space TEMP_STACK_SIZE
+        .space TEMP_STACK_SIZE
 end_stack:
 
@@ -204 +191 @@
 exception_handler:
         KERNEL_STACK_TO_K0
-        
         sub $k0, REGISTER_SPACE
         sw $sp, EOFFSET_SP($k0)
@@ -211 +197 @@
         mfc0 $k0, $cause
         
-        sra $k0, $k0, 0x2    /* cp0_exc_cause() part 1 */
-        andi $k0, $k0, 0x1f  /* cp0_exc_cause() part 2 */
-        sub $k0, 8           /* 8 = SYSCALL */
+        sra $k0, $k0, 0x2    # cp0_exc_cause() part 1
+        andi $k0, $k0, 0x1f  # cp0_exc_cause() part 2
+        sub $k0, 8           # 8 = SYSCALL
         
         beqz $k0, syscall_shortcut
-        add $k0, 8           /* revert $k0 back to correct exc number */
+        add $k0, 8           # Revert $k0 back to correct exc number
         
         REGISTERS_STORE_AND_EXC_RESET $sp
         
         move $a1, $sp
-        jal exc_dispatch     /* exc_dispatch(excno, register_space) */
+        jal exc_dispatch     # exc_dispatch(excno, register_space)
         move $a0, $k0
-        
+
         REGISTERS_LOAD $sp
-        /* the $sp is automatically restored to former value */
-        eret
-
-#define SS_SP      EOFFSET_SP
-#define SS_STATUS  EOFFSET_STATUS
-#define SS_EPC     EOFFSET_EPC
-#define SS_K1      EOFFSET_K1
-
-/** Syscall entry
- *
- * Registers:
- *
- * @param $v0 Syscall number.
- * @param $a0 1st argument.
- * @param $a1 2nd argument.
- * @param $a2 3rd argument.
- * @param $a3 4th argument.
- * @param $t0 5th argument.
- * @param $t1 6th argument.
- *
- * @return The return value will be stored in $v0.
- *
- */
+        # The $sp is automatically restored to former value
+        eret
+
+## Syscall entry
+#
+# Registers:
+#
+# @param v0             Syscall number.
+# @param a0             1st argument.
+# @param a1             2nd argument.
+# @param a2             3rd argument.
+# @param a3             4th argument.
+# @param t0             5th argument.
+# @param t1             6th argument.
+#
+# @return               The return value will be stored in v0.
+#
+#define SS_SP           EOFFSET_SP
+#define SS_STATUS       EOFFSET_STATUS
+#define SS_EPC          EOFFSET_EPC
+#define SS_K1           EOFFSET_K1
 syscall_shortcut:
-        /* we have a lot of space on the stack, with free use */
+        # We have a lot of space on the stack, with free use
         mfc0 $t3, $epc
         mfc0 $t2, $status
-        sw $t3, SS_EPC($sp)  /* save EPC */
-        sw $k1, SS_K1($sp)   /* save $k1 not saved on context switch */
-        
-        and $t4, $t2, REG_SAVE_MASK  /* save only KSU, EXL, ERL, IE */
+        sw $t3, SS_EPC($sp)             # Save EPC
+        sw $k1, SS_K1($sp)              # Save k1 not saved on context switch
+        
+        and $t4, $t2, REG_SAVE_MASK     # Save only KSU, EXL, ERL, IE
         li $t5, ~(0x1f)
-        and $t2, $t2, $t5  /* clear KSU, EXL, ERL */
-        ori $t2, $t2, 0x1  /* set IE */
-        
+        and $t2, $t2, $t5               # Clear KSU, EXL, ERL
+        ori $t2, $t2, 0x1               # Set IE
+
         sw $t4, SS_STATUS($sp)
         mtc0 $t2, $status
-        
-        /*
-         * Call the higher level system call handler.
-         * We are going to reuse part of the unused exception stack frame.
-         *
-         */
-        sw $t0, STACK_ARG4($sp)  /* save the 5th argument on the stack */
-        sw $t1, STACK_ARG5($sp)  /* save the 6th argument on the stack */
+
+        #
+        # Call the higher level system call handler
+        # We are going to reuse part of the unused exception stack frame
+        #
+        sw $t0, STACK_ARG4($sp)         # save the 5th argument on the stack
+        sw $t1, STACK_ARG5($sp)         # save the 6th argument on the stack
         jal syscall_handler
-        sw $v0, STACK_ARG6($sp)  /* save the syscall number on the stack */
-        
-        /* restore status */
+        sw $v0, STACK_ARG6($sp)         # save the syscall number on the stack
+
+        # restore status
         mfc0 $t2, $status
         lw $t3, SS_STATUS($sp)
-        
-        /*
-         * Change back to EXL = 1 (from last exception), otherwise
-         * an interrupt could rewrite the CP0 - EPC.
-         *
-         */
-        li $t4, ~REG_SAVE_MASK  /* mask UM, EXL, ERL, IE */
+
+        # Change back to EXL = 1 (from last exception), otherwise
+        # an interrupt could rewrite the CP0 - EPC
+        li $t4, ~REG_SAVE_MASK          # Mask UM, EXL, ERL, IE
         and $t2, $t2, $t4
-        or $t2, $t2, $t3  /* copy saved UM, EXL, ERL, IE */
+        or $t2, $t2, $t3                # Copy saved UM, EXL, ERL, IE
         mtc0 $t2, $status
-        
-        /* restore epc + 4 */
+                        
+        # restore epc + 4
         lw $t2, SS_EPC($sp)
         lw $k1, SS_K1($sp)
@@ -293 +273 @@
         mtc0 $t2, $epc
         
-        lw $sp, SS_SP($sp)  /* restore $sp */
-        eret
-
+        lw $sp, SS_SP($sp)              # restore sp
+        
+        eret
+                
 tlb_refill_handler:
         KERNEL_STACK_TO_K0
@@ -302 +283 @@
         sw $sp,EOFFSET_SP($k0)
         add $sp, $k0, 0
-        
+
         jal tlb_refill
         add $a0, $sp, 0 
-        
+
         REGISTERS_LOAD $sp
+
         eret
 
@@ -315 +297 @@
         sw $sp,EOFFSET_SP($k0)
         add $sp, $k0, 0
-        
+
         jal cache_error
-        add $a0, $sp, 0
-        
+        add $a0, $sp, 0 
+
         REGISTERS_LOAD $sp
+
         eret
 
 userspace_asm:
         add $sp, $a0, 0
-        add $v0, $a1, 0
-        add $t9, $a2, 0    /* set up correct entry into PIC code */
-        xor $a0, $a0, $a0  /* $a0 is defined to hold pcb_ptr */
-                           /* set it to 0 */
-        eret
+        add $v0, $a1, 0 
+        add $t9, $a2, 0                 # Set up correct entry into PIC code
+        xor $a0, $a0, $a0               # $a0 is defined to hold pcb_ptr
+                                        # set it to 0
+        eret