Next: BIOS port memory map, Previous: Error Handling, Up: GNU GRUB developer manual [Contents][Index]

## 8 Stack and heap size

On emu stack and heap are just normal host OS stack and heap. Stack is typically 8 MiB although it’s OS-dependent.

On i386-pc, i386-coreboot, i386-qemu and i386-multiboot the stack is 60KiB. All available space between 1MiB and 4GiB marks is part of heap.

On *-xen stack is 4MiB. If compiled for x86-64 with GCC 4.4 or later adressable space is unlimited. When compiled for x86-64 with older GCC version adressable space is limited to 2GiB. When compiling for i386 adressable space is limited to 4GiB. All adressable pages except the ones for stack, GRUB binary, special pages and page table are in the heap.

On *-efi GRUB uses same stack as EFI. If compiled for x86-64 with GCC 4.4 or later adressable space is unlimited. When compiled for x86-64 with older GCC version adressable space is limited to 2GiB. For all other platforms adressable space is limited to 4GiB. GRUB allocates pages from EFI for its heap, at most 1.6 GiB.

On i386-ieee1275 and powerpc-ieee1275 GRUB uses same stack as IEEE1275. It allocates at most 32MiB for its heap.

On sparc64-ieee1275 stack is 256KiB and heap is 2MiB.

On mips(el)-qemu_mips and mipsel-loongson stack is 2MiB (everything below GRUB image) and everything above GRUB image (from 2MiB + kernel size) until 256MiB is part of heap.

On mips-arc stack is 2MiB (everything below GRUB image) and everything above GRUB image(from 2MiB + kernel size) until 128MiB is part of heap.

On mipsel-arc stack is 2MiB (everything below GRUB image which is not part of ARC) and everything above GRUB image (from 7MiB + kernel size) until 256MiB is part of heap.

On arm-uboot stack is 256KiB and heap is 2MiB.

In short:

Platform | Stack | Heap
--- | --- | ---
emu | 8 MiB | ?
i386-pc | 60 KiB | < 4 GiB
i386-coreboot | 60 KiB | < 4 GiB
i386-multiboot | 60 KiB | < 4 GiB
i386-qemu | 60 KiB | < 4 GiB
*-efi | ? | < 1.6 GiB
i386-ieee1275 | ? | < 32 MiB
powerpc-ieee1275 | ? | < 32 MiB
sparc64-ieee1275 | 256KiB | 2 MiB
arm-uboot | 256KiB | 2 MiB
mips(el)-qemu_mips | 2MiB | 253 MiB
mipsel-loongson | 2MiB | 253 MiB
mips-arc | 2MiB | 125 MiB
mipsel-arc | 2MiB | 248 MiB
x86_64-xen (GCC >= 4.4) | 4MiB | unlimited
x86_64-xen (GCC < 4.4) | 4MiB | < 2GiB
i386-xen | 4MiB | < 4GiB

Next: BIOS port memory map, Previous: Error Handling, Up: GNU GRUB developer manual [Contents][Index]