mirror of
https://github.com/isometimes/rpi4-osdev
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30 lines
936 B
ArmAsm
30 lines
936 B
ArmAsm
.section ".text.boot" // Make sure the linker puts this at the start of the kernel image
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.global _start // Execution starts here
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_start:
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// Check processor ID is zero (executing on main core), else hang
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mrs x1, mpidr_el1
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and x1, x1, #3
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cbz x1, 2f
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// We're not on the main core, so hang in an infinite wait loop
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1: wfe
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b 1b
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2: // We're on the main core!
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// Set stack to start below our code
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ldr x1, =_start
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mov sp, x1
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// Clean the BSS section
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ldr x1, =__bss_start // Start address
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ldr w2, =__bss_size // Size of the section
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3: cbz w2, 4f // Quit loop if zero
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str xzr, [x1], #8
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sub w2, w2, #1
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cbnz w2, 3b // Loop if non-zero
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// Jump to our main() routine in C (make sure it doesn't return)
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4: bl main
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// In case it does return, halt the master core too
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b 1b
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