You can not select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
 
 
 
 
 

120 lines
2.9 KiB

.section .text.boot
.global __start
.type __start, %function
// From https://developer.arm.com/docs/ddi0487/ca/arm-architecture-reference-manual-armv8-for-armv8-a-architecture-profile
// ***************************************
// SCTLR_EL1, System Control Register (EL1), Page 2654 of AArch64-Reference-Manual.
// ***************************************
#define SCTLR_RESERVED (3 << 28) | (3 << 22) | (1 << 20) | (1 << 11)
#define SCTLR_EE_LITTLE_ENDIAN (0 << 25)
#define SCTLR_EOE_LITTLE_ENDIAN (0 << 24)
#define SCTLR_I_CACHE_DISABLED (0 << 12)
#define SCTLR_D_CACHE_DISABLED (0 << 2)
#define SCTLR_MMU_DISABLED (0 << 0)
#define SCTLR_MMU_ENABLED (1 << 0)
#define SCTLR_VALUE_MMU_DISABLED (SCTLR_RESERVED | SCTLR_EE_LITTLE_ENDIAN | SCTLR_I_CACHE_DISABLED | SCTLR_D_CACHE_DISABLED | SCTLR_MMU_DISABLED)
// ***************************************
// HCR_EL2, Hypervisor Configuration Register (EL2), Page 2487 of AArch64-Reference-Manual.
// ***************************************
#define HCR_RW (1 << 31)
#define HCR_VALUE HCR_RW
// ***************************************
// SCR_EL3, Secure Configuration Register (EL3), Page 2648 of AArch64-Reference-Manual.
// ***************************************
#define SCR_RESERVED (3 << 4)
#define SCR_RW (1 << 10)
#define SCR_NS (1 << 0)
#define SCR_VALUE (SCR_RESERVED | SCR_RW | SCR_NS)
// ***************************************
// SPSR_EL3, Saved Program Status Register (EL3) Page 389 of AArch64-Reference-Manual.
// ***************************************
#define SPSR_MASK_ALL (7 << 6)
#define SPSR_EL1h (5 << 0)
#define SPSR_VALUE (SPSR_MASK_ALL | SPSR_EL1h)
#define SIMD_ENABLE (3 << 20)
__start:
//Use core 0 only
mrs x7, mpidr_el1
and x7, x7, #3
cbz x7, __switch_level
0: wfe
b 0b
__switch_level:
mrs x0, CurrentEL
lsr x0, x0, #2 // Shift Right by 2
and x0, x0, #3
cmp x0, #3
beq __switch_l3_l1
b __switch_l2_l1
__switch_l3_l1:
ldr x0, =SCTLR_VALUE_MMU_DISABLED
msr sctlr_el1, x0
ldr x0, =HCR_VALUE
msr hcr_el2, x0
ldr x0, =SCR_VALUE
msr scr_el3, x0
ldr x0, =SPSR_VALUE
msr spsr_el3, x0
mrs x0, CPACR_EL1
and x0, x0, #SIMD_ENABLE
msr CPACR_EL1, x0
adr x0, __start_master
msr elr_el3, x0
eret
__switch_l2_l1:
ldr x0, =SCTLR_VALUE_MMU_DISABLED
msr sctlr_el1, x0
ldr x0, =HCR_VALUE
msr hcr_el2, x0
ldr x0, =SPSR_VALUE
msr spsr_el2, x0
mrs x0, CPACR_EL1
and x0, x0, #SIMD_ENABLE
msr CPACR_EL1, x0
adr x0, __start_master
msr elr_el2, x0
eret
__start_master:
//Setup stack pointer
ldr x2, = __stack_start
mov sp, x2
//Clear BSS
ldr w0, = __bss_start
ldr w1, = __bss_size
1: cbz x1, 2f
str xzr, [x0], #8
sub x1, x1, #1
cbnz x1, 1b
2:
bl kernelmain
b 0b