Can we automatically determine the value of RAMTOP during build time? On 17.12.2010, at 12:29, Patrick Georgi <[email protected]> wrote:
> Am Freitag, 17. Dezember 2010, um 15:08:38 schrieb Fengwei Zhang: >> I would appreciate if someone could explain a little bit for me. >> CONFIG_DCACHE_RAM_BASE >> CONFIG_DCACHE_RAM_SIZE >> CONFIG_RAMTOP > DCACHE_RAM_BASE is the start address of the memory addresses that are used > for > CAR. > > DCACHE_RAM_SIZE is the size of that region. > > RAMTOP is the highest address of the memory region that coreboot will use in > RAM. > >> In addition, why do we need to set new esp here? >> /* set new esp */ /* before CONFIG_RAMBASE */ >> "subl %0, %%esp\n\t" >> >> ::"a"( (CONFIG_DCACHE_RAM_BASE + CONFIG_DCACHE_RAM_SIZE)- >> (CONFIG_RAMTOP) ) > This moves the stack from CAR area to RAM. > > While in CAR, the stack is laid out at the top end of CAR, growing downwards > (ie. starting at DCACHE_RAM_BASE + DCACHE_RAM_SIZE). > While in RAM, it starts at the top end of the ram area used for coreboot > (RAMTOP). > > Before that line the stack is copied from CAR to RAM, then esp is setup so it > points to the same place in RAM that it pointed to in CAR (that's why we use > sub, not mov). > This setup doesn't allow returning from the current function (we don't adjust > addresses on the stack), but it makes sure that local variables in the scope > of the current function are still usable. > > > Hope this helps, > Patrick > > -- > coreboot mailing list: [email protected] > http://www.coreboot.org/mailman/listinfo/coreboot > -- coreboot mailing list: [email protected] http://www.coreboot.org/mailman/listinfo/coreboot
