On Thu, 2012-03-08 at 22:57:30 +0000, Julian Pidancet wrote: > On Wed, Mar 7, 2012 at 7:04 PM, Guillem Jover <[email protected]> wrote: > > On Wed, 2012-03-07 at 17:54:57 +0000, Julian Pidancet wrote: > > > So according to the manual, it should be BP, not EBP. > > > > The register being decreased should match the one being used to address > > the stack, and the one to use depends on the descriptor as per above. > > There is no "descriptor" in real mode. Default stack size is always 16-bit.
Certainly! And sorry, somehow missed the fact this is exclusively real-mode being emulated. > Also, I think the right thing to do is to decrement BP instead of EBP > when SYSMODE_PREFIX_DATA is set: > > M.x86.R_BP -= 4; > push_long(fetch_data_long_abs(M.x86.R_SS, M.x86.R_BP)); > > instead of: > > M.x86.R_EBP -= 4; > push_long(fetch_data_long_abs(M.x86.R_SS, M.x86.R_BP)); > > ...to remain exactly consistent with the manual. Indeed. > > > In any case, It won't be a problem, because the 16 high bits of EBP > > > will most likely be zero in real-mode code. > > > > Well, not if the the code is using some 32-bit instructions. :) > They are not "32-bit instructions". The processor is still functioning > in real-mode, therefore, addressing still follows the rules of > real-mode addressing, as mentioned in Volume 1:Basic Architecture : > 3.3.5 32-Bit and 16-Bit Address and Operand Sizes Regardless of the mode, if the instructions are being modified by the prefixes to use 32-bit operands or addresses, they are in my book 32-bit instructions. In any case what I meant was that ebp can have any value because the register can be assigned directly, for example, and wrap-around might vary depending on what part of it it's being operated on. thanks, guillem _______________________________________________ [email protected]: X.Org development Archives: http://lists.x.org/archives/xorg-devel Info: http://lists.x.org/mailman/listinfo/xorg-devel
