Wrap the mmap2 syscall

boot/common-boot.s

@@ -5,17 +5,22 @@
 .global _is_alpha, _is_digit, _is_alnum, _is_upper, _is_lower
 .global _write_out, _read_file, _write_error, _put_char, _printi
 .global _get, _memcmp, _memchr, _memmem, _memcpy
-.global _divide_by_zero_error, _exit
-.global _strings_index
+.global _divide_by_zero_error, _exit, _mmap
+.global _strings_index, _string_equal
 
 .section .rodata
 
 .equ SYS_READ, 63
 .equ SYS_WRITE, 64
 .equ SYS_EXIT, 93
+.equ SYS_MMAP2, 222
 .equ STDIN, 0
 .equ STDOUT, 1
 .equ STDERR, 2
+.equ PROT_READ, 0x1
+.equ PROT_WRITE, 0x2
+.equ MAP_PRIVATE, 0x02
+.equ MAP_ANONYMOUS, 0x20
 
 new_line: .ascii "\n"
 
@@ -500,3 +505,58 @@ _strings_index:
 	lw s0, 24(sp)
 	add sp, sp, 32
 	ret
+
+# Compares two strings for equality.
+#
+# Parameters:
+# a0 - Length of the first string.
+# a1 - Pointer to the first string.
+# a2 - Length of the second string.
+# a3 - Pointer to the second string.
+#
+# Sets a0 to 1 if the string are equal, to 0 if not.
+.type _string_equal, @function
+_string_equal:
+	# Prologue.
+	addi sp, sp, -32
+	sw ra, 28(sp)
+	sw s0, 24(sp)
+	addi s0, sp, 32
+
+	# Compare string lengths.
+	bne a0, a2, .Lstring_equal_not_found
+
+	# If lengths match, compare the content.
+	mv a0, a1
+	mv a1, a3
+	# a2 is already set to the length.
+	call _memcmp
+
+	bnez a0, .Lstring_equal_not_found
+
+	li a0, 1
+	j .Lstring_equal_end
+
+.Lstring_equal_not_found:
+	mv a0, zero
+
+.Lstring_equal_end:
+	# Epilogue.
+	lw ra, 28(sp)
+	lw s0, 24(sp)
+	addi sp, sp, 32
+	ret
+
+# Sets a0 to the mapping address.
+.type _mmap, @function
+_mmap:
+	li a0, 0 # Address at which to create the mapping.
+	li a1, 4096 # The length of the mapping.
+	li a2, PROT_READ | PROT_WRITE # Protection flags.
+	li a3, MAP_ANONYMOUS | MAP_PRIVATE # The mapping is not backed by a file.
+	li a4, -1 # File descriptor.
+	li a5, 0 # Page offset.
+	li a7, SYS_MMAP2
+	ecall
+
+	ret