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WIP: added reset support for qemu using semihosting in aarch64-virt #40

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Merged
andoma merged 1 commit into from
Jan 15, 2026
Merged

WIP: added reset support for qemu using semihosting in aarch64-virt #40

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16 changes: 16 additions & 0 deletions src/platform/aarch64-virt/aarch64-virt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,11 @@

#include "drivers/pl011.h"

// Semihosting definitions
#define SEMIHOSTING_SYS_EXIT 0x18
#define ADP_STOPPED_APPLICATION_EXIT 0x20026
extern uintptr_t semihosting_call(uint32_t reason, uintptr_t arg);

long
gicr_base(void)
{
Expand All @@ -22,9 +27,20 @@ board_init_early(void)
printf("ID_AA64MMFR0_EL1 = %lx\n", wut);
}

void
semihosting_exit(uint32_t reason, uint32_t subcode)
{
uint64_t parameters[] = {reason, subcode};

(void)semihosting_call(SEMIHOSTING_SYS_EXIT, (uintptr_t)&parameters);
}

void
reboot(void)
{
semihosting_exit(ADP_STOPPED_APPLICATION_EXIT, 0);
// should not reach here

printf("Reboot not implemented, stalling forever\n");

while(1) {
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4 changes: 2 additions & 2 deletions src/platform/aarch64-virt/aarch64-virt.mk
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Expand Up @@ -20,10 +20,10 @@ GDB_PORT ?= 1234
GDB_HOST ?= 127.0.0.1

qemu: ${O}/build.elf
qemu-system-aarch64 -M virt,gic-version=3,virtualization=on -cpu cortex-a57 -nographic -kernel $< -s -S
qemu-system-aarch64 -M virt,gic-version=3,virtualization=on -semihosting -cpu cortex-a57 -nographic -kernel $< -s -S

run: ${O}/build.elf
qemu-system-aarch64 -m 8192 -M virt,gic-version=3 -cpu cortex-a57 -nographic -kernel $<
qemu-system-aarch64 -m 8192 -M virt,gic-version=3 -semihosting -cpu cortex-a57 -nographic -kernel $<

gdb: ${O}/build.elf
${GDB} -ex "target extended-remote ${GDB_HOST}:${GDB_PORT}" -ex "layout asm" -ex "layout regs" -x ${T}/gdb/macros $<
5 changes: 5 additions & 0 deletions src/platform/aarch64-virt/asm.S
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Expand Up @@ -6,3 +6,8 @@ putc:
tbnz w2, #5, 1b
str x0, [x1]
ret

.globl semihosting_call
semihosting_call:
hlt #0xf000
ret