Move kernel_main into the elna code
This commit is contained in:
@@ -31,14 +31,18 @@ _start:
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mv a0, s2
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mv a1, sp
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call get_page_tables_size
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mv a3, a0
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mv a0, s2
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mv a1, sp
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mv a2, s4
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mv a1, s2
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mv a2, sp
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mv a3, s4
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jal imem_initialize
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mv a0, s3
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mv a1, s3
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jal imem_mirror
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# Save the address where the initial page tables end in a variable.
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add a0, a0, s3
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la t0, pmem_address
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sw a0, (t0)
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call set_up_trap_routine
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add sp, sp, s4 # Move the stack to the virtual memory.
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@@ -48,11 +52,10 @@ _start:
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mv a1, sp
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call imem_zero
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mv a0, sp
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mv a1, s1
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mv a0, s1
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lui t0, %hi(kernel_main)
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jr t0, %lo(kernel_main)
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lui t0, %hi(device_tree)
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jr t0, %lo(device_tree)
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# Given the start and end addresses of the kernel, calculates how
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# much additional storage should be mapped to store the page tables.
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@@ -74,6 +77,8 @@ _start:
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# Returns the result in a0.
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.type get_page_tables_size, @function
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get_page_tables_size:
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li t0, 0xffc00000
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and a0, a0, t0
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sub a0, a1, a0
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srli a0, a0, 22
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@@ -119,7 +124,11 @@ imem_zero:
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# Copies the identity mappings to the higher half.
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#
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# Parameters:
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# a0 - Start of the kernel virtual space.
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# a0 - Size of additional page tables.
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# a1 - Start of the kernel virtual space.
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#
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# Returns a pointer pointing to the end of the last page table
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# with higher half mappings in a0.
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.type imem_mirror, @function
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imem_mirror:
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csrr t0, satp
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@@ -127,12 +136,14 @@ imem_mirror:
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li t3, PAGE_SIZE
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add t1, t0, t3 # Original page table.
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add t2, t1, t3 # Copied page table.
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add t2, t1, a0 # Copied page table.
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li t5, 0xffffffcf
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mv t3, t2
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.Limem_mirror_copy:
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lw t4, (t1)
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and t4, t4, t5 # Clear "dirty" and "accessed" bits.
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sw t4, (t3)
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addi t3, t3, 4
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@@ -140,11 +151,13 @@ imem_mirror:
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blt t1, t2, .Limem_mirror_copy
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# Persist the copied page table in the root page table.
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srli t4, a0, 20 # VPN[1] * PTESIZE.
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srli t4, a1, 20 # VPN[1] * PTESIZE.
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add t4, t0, t4 # a + VPN[1] * PTESIZE.
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srli t3, t2, 2
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ori t3, t3, 0b1
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sw t3, (t4)
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srli t5, t2, 2
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ori t5, t5, 0b1
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sw t5, (t4)
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mv a0, t3
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ret
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@@ -152,10 +165,12 @@ imem_mirror:
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# Allocates enough pages for the kernel and its stack.
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#
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# Parameters:
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# a0 - Physical start of the text section.
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# a1 - Page aligned address following the kernel (kernel end).
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# a2 - Offset from the physical to virtual memory.
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# a3 - Size of additional page tables.
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# a0 - Size of additional page tables.
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# a1 - Physical start of the text section.
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# a2 - Page aligned address following the kernel (kernel end).
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# a3 - Offset from the physical to virtual memory.
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#
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# Returns the size of the created page tables (a0) in a0.
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.type imem_initialize, @function
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imem_initialize:
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# Prologue.
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@@ -164,55 +179,54 @@ imem_initialize:
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sw s0, 24(sp)
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addi s0, sp, 32
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sw a0, 20(sp)
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sw s1, 16(sp)
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sw s2, 12(sp)
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sw s3, 8(sp)
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sw a0, 4(sp)
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sw a1, 4(sp)
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# Set s1 to the beginning of free memory (skipping root page table).
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li s1, PAGE_SIZE
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add s1, a1, s1
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slli a3, a3, 1 # Multiply by two to account for the copy in virtual memory.
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# s1 is a1 + PAGE, where PAGE is a free page reserved for future use,
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# since the size of the root page table is already included in a3.
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# s1 is used to avoid calculating a1 + PAGE_SIZE twice.
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add a3, s1, a3
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sw a3, 20(sp)
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add s1, a2, s1
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# Set boundaries between segments.
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lui s2, %hi(etext)
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sub s2, s2, a2
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sub s2, s2, a3
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lui s3, %hi(_data)
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sub s3, s3, a2
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sub s3, s3, a3
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# Set the root page since it is used by mapping functions,
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# but don't activate paging before the segments are property mapped.
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srli t0, a1, 12
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srli t0, a2, 12
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csrw satp, t0
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# Zero memory for page tables.
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mv a0, a1
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add a1, s1, a3
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mv a0, a2
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add a1, s1, a0
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call imem_zero
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# Executable section.
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mv a0, s1
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lw a1, 4(sp)
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addi a2, s2, %lo(etext)
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li a3, 0b1010 # Read and execute.
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li a3, PAGE_READ | PAGE_EXECUTE
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jal imem_map_range
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# Read only section.
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addi a1, s2, %lo(etext)
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addi a2, s3, %lo(_data)
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li a3, 0b0010 # Read.
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li a3, PAGE_READ
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jal imem_map_range
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# Data section.
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addi a1, s3, %lo(_data)
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lw a2, 20(sp)
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li a3, 0b0110 # Read and write.
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slli a2, a2, 1 # Multiply by two to account for the copy in virtual memory.
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# s1 is a2 + PAGE, where PAGE is a free page reserved for future use,
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# since the size of the root page table is already included in a0.
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# s1 is used to avoid calculating a2 + PAGE_SIZE twice.
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add a2, s1, a2
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li a3, PAGE_READ | PAGE_WRITE
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jal imem_map_range
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# Enable paging.
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@@ -227,6 +241,7 @@ imem_initialize:
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lw s3, 8(sp)
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lw s2, 12(sp)
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lw s1, 16(sp)
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lw a0, 20(sp)
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# Epilogue.
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lw ra, 28(sp)
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@@ -338,40 +353,6 @@ imem_map_at:
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.section .text
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.type kernel_main, @function
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kernel_main:
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# Prologue.
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addi sp, sp, -32
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sw ra, 28(sp)
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sw s0, 24(sp)
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addi s0, sp, 32
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sw a0, 20(sp)
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sw a1, 16(sp)
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# Map flat device tree to the virtual memory.
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lw a0, 16(sp)
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li t0, 0xffc00000
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and a0, a0, t0
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mv a1, a0
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lw a2, 20(sp)
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li a3, 0
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li a4, 0b0010
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call pmem_map_at
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lw a0, 16(sp)
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call device_tree
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# Do nothing in a loop.
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.Lkernel_main:
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j .Lkernel_main
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# Epilogue.
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lw ra, 28(sp)
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lw s0, 24(sp)
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addi sp, sp, 32
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ret
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.balign 4
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.type trap_routine, @function
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trap_routine:
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