On 08/13/2018 12:56 PM, Stefan Hajnoczi wrote: > On Fri, Aug 10, 2018 at 02:00:44AM -0300, Philippe Mathieu-Daudé wrote: >> On 08/03/2018 11:47 AM, Stefan Hajnoczi wrote: >>> + parser->rom_start_address = parser->next_address_to_write; >>> + parser->current_rom_index = 0; >>> + break; >>> + >>> + case START_SEG_ADDR_RECORD: >>> + if (line->byte_count != 4 && line->address != 0) { >>> + return -1; >>> + } >>> + >>> + /* x86 16-bit CS:IP segmented addressing */ >>> + *(parser->start_addr) = (((line->data[0] << 8) | line->data[1]) << >>> 4) | >>> + (line->data[2] << 8) | line->data[3]; >> >> Can you add a qtest for this case? >> For the HEX loader I understand the specs as this is the same parsing as >> the START_LINEAR_ADDR_RECORD case; so I disagree with data[0] and >> data[1] shifts. > > x86 real-mode CS:IP addressing means (CS << 4) + IP. It produces 24-bit > addresses on 80286 and later. This is not the same as > START_LINEAR_ADDR_RECORD.
OK! > > GNU bfd implements it as follows: > > abfd->start_address += (HEX4 (buf) << 4) + HEX4 (buf + 4); Hmm any idea why they use +4 ? > > https://sourceware.org/git/?p=binutils.git;a=blob;f=bfd/ihex.c;h=09f756a1c2c11e57c5da15a6ff96491275575b86;hb=HEAD#l415 > > Thanks for commenting on this, I had written (CS << 4) | IP instead of > (CS << 4) + IP. This will be fixed in the next revision. > >> This is different for the consumer (i386 expects 2 16-bit registers but >> HexParser->start_addr is a hwaddr, used as a single (at least) 32-bit >> register. > > I think you're saying that on x86 the guest CS:IP registers should be > set. This loader is never called from hw/i386/ so it doesn't matter at > this time. OK. > > GNU bfd uses START_SEG_ADDR_RECORD records on non-x86 architectures > where there are no segment registers and that's where we've encountered > them. >
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