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Add assembly constants file

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This commit is contained in:
Eugen Wissner
2025-08-02 00:12:28 +02:00
parent 3e50e74526
commit badac1378d
3 changed files with 133 additions and 67 deletions
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69
arch/riscv/common.s
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@@ -2,6 +2,8 @@
# v. 2.0. If a copy of the MPL was not distributed with this file, You can
# obtain one at https://mozilla.org/MPL/2.0/.
.include "./arch/riscv/constants.s"
.section .text
# a0 - First pointer.
@@ -237,3 +239,70 @@ memset:
.Lmemset_end:
ret
# Maps a page of physical memory to the identical virtual memory.
#
# Parameters:
# a0 - Corresponding virtual address.
# a1 - Physical page address.
# a2 - Free memory page that can be used to create a leaf page table.
# a3 - Page table level. If a3 is 0 a superpage is allocated, otherwise a normal page.
# a4 - Flags.
#
# If the function creates new page tables in a2, it advances a2 by the page size and
# returns it in a0.
.type pmem_map_at, @function
.globl pmem_map_at
pmem_map_at:
csrr t0, satp
slli t0, t0, 12 # Root table address.
li t4, 0xfffffc00
li t5, 0xffc # 10 bit * PTESIZE mask.
li t1, 20
.Lpmem_map_at_loop:
# Multiply VPN[i] by 4 and add to the start address of the page table.
# This gives the physical address of the page table entry.
srl t2, a0, t1
and t2, t2, t5 # VPN[i] * PTESIZE.
add t2, t0, t2 # a + VPN[i] * PTESIZE.
beqz a3, .Lpmem_map_at_leaf
lw t3, (t2)
andi t6, t3, 0b1
beqz t6, .Lpmem_map_at_create
and t0, t3, t4
slli t0, t0, 2
j .Lpmem_map_at_next
.Lpmem_map_at_create:
# Take a chunk of free memory and use it as the next page table.
# The beginning addres off the chunk is the base address (a) for the next level.
mv t0, a2
srli t3, t0, 2
ori t3, t3, 0b1
sw t3, (t2)
li t6, PAGE_SIZE
add a2, a2, t6
.Lpmem_map_at_next:
# Calculate the next page table address for the next level.
addi t1, t1, -10
addi a3, a3, -1
j .Lpmem_map_at_loop
.Lpmem_map_at_leaf:
srli t3, a1, 2 # Physical page number mapped to 12 bits of the page table entry.
ori a4, a4, 0b1
or t3, t3, a4 # Execute, write, read and valid.
sw t3, (t2)
mv a0, a2
ret

1
arch/riscv/constants.s Normal file
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@@ -0,0 +1 @@
.equ PAGE_SIZE, 4096

130
arch/riscv/kernel.s
View File

@@ -2,6 +2,8 @@
# v. 2.0. If a copy of the MPL was not distributed with this file, You can
# obtain one at https://mozilla.org/MPL/2.0/.
.include "./arch/riscv/constants.s"
.section .rodata
panic_message: .asciz "\nPanic"
@@ -104,12 +106,10 @@ set_up_stack:
# a1 - Memory end pointer.
.type imem_zero, @function
imem_zero:
mv t0, a0
.Limem_zero_loop:
bgeu t0, a1, .Limem_zero_end
sw zero, (t0)
addi t0, t0, 4
bgeu a0, a1, .Limem_zero_end
sw zero, (a0)
addi a0, a0, 4
j .Limem_zero_loop
@@ -125,7 +125,7 @@ imem_mirror:
csrr t0, satp
slli t0, t0, 12
li t3, 0x1000
li t3, PAGE_SIZE
add t1, t0, t3 # Original page table.
add t2, t1, t3 # Copied page table.
@@ -167,9 +167,10 @@ imem_initialize:
sw s1, 16(sp)
sw s2, 12(sp)
sw s3, 8(sp)
sw a0, 4(sp)
# Set s1 to the beginning of free memory (skipping root page table).
li s1, 4096
li s1, PAGE_SIZE
add s1, a1, s1
slli a3, a3, 1 # Multiply by two to account for the copy in virtual memory.
@@ -190,28 +191,28 @@ imem_initialize:
srli t0, a1, 12
csrw satp, t0
# Zero memory for page tables.
mv a0, a1
add a1, s1, a3
call imem_zero
# Executable section.
# a0 is coming from the parameter.
addi a1, s2, %lo(etext)
mv a2, s1
li a3, 1
li a4, 0b1010
mv a0, s1
lw a1, 4(sp)
addi a2, s2, %lo(etext)
li a3, 0b1010 # Read and execute.
jal imem_map_range
# Read only section.
addi a0, s2, %lo(etext)
addi a1, s3, %lo(_data)
mv a2, s1
li a3, 1
li a4, 0b0010
addi a1, s2, %lo(etext)
addi a2, s3, %lo(_data)
li a3, 0b0010 # Read.
jal imem_map_range
# Data section.
addi a0, s3, %lo(_data)
lw a1, 20(sp)
mv a2, s1
li a3, 1
li a4, 0b0110
addi a1, s3, %lo(_data)
lw a2, 20(sp)
li a3, 0b0110 # Read and write.
jal imem_map_range
# Enable paging.
@@ -236,11 +237,12 @@ imem_initialize:
# Maps multiple pages of physical memory to the identical virtual memory.
#
# Parameters:
# a0 - Start address.
# a1 - End address.
# a2 - Start of the free memory that can be used to create leaf page tables.
# a3 - Page table level. If a3 is 0 a superpage is allocated, otherwise a normal page.
# a4 - Flags.
# a0 - Start of the free memory that can be used to create leaf page tables.
# a1 - Start address.
# a2 - End address.
# a3 - Flags.
#
# If the function creates new page tables it advances and returns a0.
.type imem_map_range, @function
imem_map_range:
# Prologue.
@@ -250,27 +252,30 @@ imem_map_range:
addi s0, sp, 32
sw s1, 20(sp)
sw a2, 16(sp)
sw a3, 12(sp)
sw a4, 8(sp)
sw s2, 16(sp)
sw s3, 12(sp)
sw s4, 8(sp)
mv s1, a1
mv s2, a2
li s3, PAGE_SIZE
mv s4, a3
.Limem_map_range_loop:
bge a0, s1, .Limem_map_range_end
bge s1, s2, .Limem_map_range_end
mv a1, a0
lw a2, 16(sp)
lw a3, 12(sp)
lw a4, 8(sp)
mv a1, s1
mv a2, s4
jal imem_map_at
li t0, 4096
add a0, a0, t0
add s1, s1, s3
j .Limem_map_range_loop
.Limem_map_range_end:
lw s4, 8(sp)
lw s3, 12(sp)
lw s2, 16(sp)
lw s1, 20(sp)
# Epilogue.
@@ -282,62 +287,53 @@ imem_map_range:
# Maps a page of physical memory to the identical virtual memory.
#
# Parameters:
# a0 - Corresponding virtual address.
# a0 - Free memory page that can be used to create a leaf page table.
# a1 - Physical page address.
# a2 - Free memory page that can be used to create a leaf page table.
# a3 - Page table level. If a3 is 0 a superpage is allocated, otherwise a normal page.
# a4 - Flags.
# a2 - Flags.
#
# Returns virtual page address in a0.
# If the function creates new page tables it advances and returns a0.
.type imem_map_at, @function
imem_map_at:
csrr t0, satp
slli t0, t0, 12 # Root table address.
li t4, 0xfffffc00
li t5, 0xffc # 10 bit * PTESIZE mask.
li t1, 20
li t1, 0xffc # 10 bit * PTESIZE mask.
.Limem_map_at_loop:
# Multiply VPN[i] by 4 and add to the start address of the page table.
# This gives the physical address of the page table entry.
srl t2, a0, t1
and t2, t2, t5 # VPN[i] * PTESIZE.
add t2, t0, t2 # a + VPN[i] * PTESIZE.
beqz a3, .Limem_map_at_leaf
srli t2, a1, 20
and t2, t2, t1 # VPN[1] * PTESIZE.
add t2, t0, t2 # a + VPN[1] * PTESIZE.
lw t3, (t2)
andi t6, t3, 0b1
andi t4, t3, 0b1
beqz t6, .Limem_map_at_create
beqz t4, .Limem_map_at_create
li t4, 0xfffffc00
and t0, t3, t4
slli t0, t0, 2
j .Limem_map_at_next
j .Limem_map_at_existing
.Limem_map_at_create:
# Take a chunk of free memory and use it as the next page table.
# The beginning addres off the chunk is the base address (a) for the next level.
mv t0, a2
mv t0, a0
srli t3, t0, 2
ori t3, t3, 0b1
sw t3, (t2)
.Limem_map_at_next:
# Calculate the next page table address for the next level.
addi t1, t1, -10
addi a3, a3, -1
li t4, PAGE_SIZE
add a0, a0, t4
j .Limem_map_at_loop
.Limem_map_at_existing:
srli t2, a1, 10
and t2, t2, t1 # VPN[0] * PTESIZE.
add t2, t0, t2 # a + VPN[0] * PTESIZE.
.Limem_map_at_leaf:
srli t3, a1, 2 # Physical page number mapped to 12 bits of the page table entry.
ori a4, a4, 0b1
or t3, t3, a4 # Execute, write, read and valid.
ori a2, a2, 0b1
or t3, t3, a2 # Execute, write, read and valid.
sw t3, (t2)
ret
.section .text
@@ -361,7 +357,7 @@ kernel_main:
lw a2, 20(sp)
li a3, 0
li a4, 0b0010
call imem_map_at
call pmem_map_at
lw a0, 16(sp)
call device_tree