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https://github.com/limine-bootloader/limine
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chainload: BIOS: do not rely on 0x7c00 being free
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@ -21,7 +21,7 @@
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#if defined (BIOS)
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__attribute__((noinline, section(".realmode")))
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noreturn static void spinup(uint8_t drive) {
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noreturn static void spinup(uint8_t drive, void *buf) {
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struct idtr real_mode_idt;
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real_mode_idt.limit = 0x3ff;
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real_mode_idt.ptr = 0;
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@ -30,6 +30,14 @@ noreturn static void spinup(uint8_t drive) {
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"cli\n\t"
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"cld\n\t"
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// Safe stack location
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"mov $0x7c00, %%esp\n\t"
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// move buffer to final location
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"mov $0x7c00, %%edi\n\t"
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"mov $512, %%ecx\n\t"
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"rep movsb\n\t"
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"lidt (%%eax)\n\t"
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"pushl $0x08\n\t"
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@ -65,7 +73,7 @@ noreturn static void spinup(uint8_t drive) {
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".code32\n\t"
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:
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: "a" (&real_mode_idt), "d" (drive)
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: "a" (&real_mode_idt), "d" (drive), "S"(buf)
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: "memory"
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);
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@ -177,15 +185,17 @@ load:
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void bios_chainload_volume(struct volume *p) {
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vga_textmode_init(false);
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volume_read(p, (void *)0x7c00, 0, 512);
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void *buf = ext_mem_alloc(512);
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volatile uint16_t *boot_sig = (volatile uint16_t *)0x7dfe;
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volume_read(p, buf, 0, 512);
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uint16_t *boot_sig = (uint16_t *)(buf + 0x1fe);
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if (*boot_sig != 0xaa55) {
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return;
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}
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spinup(p->drive);
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spinup(p->drive, buf);
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}
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#elif defined (UEFI)
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