Changeset 1b109cb in mainline for arch/mips32/src/start.S

Timestamp:

2006-03-20T13:39:56Z (19 years ago)

Author:

Ondrej Palkovsky <ondrap@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

9d3e185

Parents:

8d25b44

Message:

Cleanup of mips

• inline register reads
• better fpu disable/enable - global settings is automatically propagated to task
• fast syscall

File:

• arch/mips32/src/start.S (modified) (8 diffs)

arch/mips32/src/start.S

@@ -44 +44 @@
 .global userspace_asm
 
+# 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 $at on the way
-.macro REGISTERS_STORE r
+# We will change status: Disable ERL,EXL,UM,IE
+# These changes will be automatically reversed in REGISTER_LOAD
+.macro REGISTERS_STORE_AND_EXC_RESET r
         sw $at,EOFFSET_AT(\r)
         sw $v0,EOFFSET_V0(\r)
@@ -86 +90 @@
         sw $sp,EOFFSET_SP(\r)
 
-        mfc0 $at, $status
-        sw $at,EOFFSET_STATUS(\r)
-        mfc0 $at, $epc
-        sw $at,EOFFSET_EPC(\r)
+        mfc0 $t0, $status
+        mfc0 $t1, $epc
+        
+        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
+        mfc0 $t0, $status
+        lw $t1,EOFFSET_STATUS(\r)
+
+        li $t2, ~REG_SAVE_MASK    # Mask UM,EXL,ERL,IE
+        and $t0, $t0, $t2
+        
+        or $t0, $t0, $t1   # Copy UM,EXL,ERL,IE from saved status
+        mtc0 $t0, $status
+        
         lw $v0,EOFFSET_V0(\r)
         lw $v1,EOFFSET_V1(\r)
@@ -129 +150 @@
         mthi $at
 
-        lw $at,EOFFSET_STATUS(\r)
-        mtc0 $at, $status
         lw $at,EOFFSET_EPC(\r)
         mtc0 $at, $epc
@@ -189 +208 @@
 exception_handler:
         KERNEL_STACK_TO_K0
+        
+        mfc0 $k1, $cause
         sub $k0, REGISTER_SPACE
-        REGISTERS_STORE $k0
-        add $sp, $k0, 0
-
-        add $a0, $sp, 0 
-        jal exception /* exception(register_space) */
-        nop
+        
+        sra $k1, $k1, 0x2     # cp0_exc_cause() part 1
+        andi $k1, $k1, 0x1f   # cp0_exc_cause() part 2
+        sub $k1, 8            # 8=SYSCALL
+        
+        beqz $k1, uspace_shortcut
+        add $k1, 8            # Revert $k1 back to correct exc number
+        
+        REGISTERS_STORE_AND_EXC_RESET $k0
+        move $sp, $k0
+        
+        move $a1, $sp
+        jal exc_dispatch      # exc_dispatch(excno, register_space)
+        move $a0, $k1
 
         REGISTERS_LOAD $sp
@@ -201 +230 @@
         eret
         nop
+
+# it seems that mips reserves some space on stack for varfuncs???
+#define SS_ARG4   16
+#define SS_SP     20
+#define SS_STATUS 24
+#define SS_EPC    28
+#define SS_RA     32
+uspace_shortcut:
+        # We have a lot of space on the stack, with free use
+        sw $sp, SS_SP($k0)
+        move $sp, $k0
+        sw $ra, SS_RA($k0)
+
+        mfc0 $t1, $epc
+        mfc0 $t0, $status
+        sw $t1,SS_EPC($sp)  # Save EPC
+        
+        and $t2, $t0, REG_SAVE_MASK # Save only KSU,EXL,ERL,IE
+        li $t3, ~(0x1f)
+        and $t0, $t0, $t3           # Clear KSU,EXL,ERL
+        ori $t0, $t0, 0x1           # Set IE
+
+        sw $t2,SS_STATUS($sp)
+        mtc0 $t0, $status
+
+        jal syscall_handler
+        sw $v0, SS_ARG4($sp)        # save v0 - arg4 to stack
+
+        # Restore RA
+        lw $ra, SS_RA($sp)
+        
+        # restore epc+4
+        lw $t0,SS_EPC($sp)
+        addi $t0, $t0, 4
+        mtc0 $t0, $epc
+        
+        # restore status
+        mfc0 $t0, $status
+        lw $t1,SS_STATUS($sp)
+
+        li $t2, ~REG_SAVE_MASK      # Mask UM,EXL,ERL,IE
+        and $t0, $t0, $t2
+        or $t0, $t0, $t1            # Copy UM,EXL,ERL,IE from saved status
+        mtc0 $t0, $status
+                        
+        lw $sp,SS_SP($sp) # restore sp
+        
+        eret
         
 tlb_refill_handler:
         KERNEL_STACK_TO_K0
         sub $k0, REGISTER_SPACE
-        REGISTERS_STORE $k0
+        REGISTERS_STORE_AND_EXC_RESET $k0
         add $sp, $k0, 0
 
@@ -215 +292 @@
 
         eret
-        nop
 
 cache_error_handler:
         KERNEL_STACK_TO_K0
         sub $sp, REGISTER_SPACE
-        REGISTERS_STORE $sp
+        REGISTERS_STORE_AND_EXC_RESET $sp
         add $sp, $k0, 0
 
@@ -229 +305 @@
 
         eret
-        nop
 
 userspace_asm:
@@ -235 +310 @@
         add $v0, $a1, 0
         eret
-        nop
-
+