On 10.04.2025 09:20, Roger Pau Monné wrote:
> On Tue, Apr 08, 2025 at 02:34:48PM +0200, Jan Beulich wrote:
>> On 08.04.2025 13:21, Roger Pau Monné wrote:
>>> On Wed, Apr 02, 2025 at 09:46:53AM +0200, Jan Beulich wrote:
>>>> @@ -54,31 +56,40 @@ static unsigned int load(const char *nam
>>>>
>>>> if ( lseek(in, mz_hdr.peaddr, SEEK_SET) < 0 ||
>>>> read(in, &pe_hdr, sizeof(pe_hdr)) != sizeof(pe_hdr) ||
>>>> - read(in, &pe32_opt_hdr, sizeof(pe32_opt_hdr)) !=
>>>> sizeof(pe32_opt_hdr) ||
>>>> - read(in, &base, sizeof(base)) != sizeof(base) ||
>>>> - /*
>>>> - * Luckily the image size field lives at the
>>>> - * same offset for both formats.
>>>> - */
>>>> - lseek(in, 24, SEEK_CUR) < 0 ||
>>>> - read(in, image_size, sizeof(*image_size)) != sizeof(*image_size)
>>>> )
>>>> + (read(in, &pe32_opt_hdr.pe, sizeof(pe32_opt_hdr.pe)) !=
>>>> + sizeof(pe32_opt_hdr.pe)) )
>>>> {
>>>> perror(name);
>>>> exit(3);
>>>> }
>>>>
>>>> switch ( (pe_hdr.magic == PE_MAGIC &&
>>>> - pe_hdr.opt_hdr_size > sizeof(pe32_opt_hdr)) *
>>>> - pe32_opt_hdr.magic )
>>>> + pe_hdr.opt_hdr_size > sizeof(pe32_opt_hdr.pe)) *
>>>> + pe32_opt_hdr.pe.magic )
>>>> {
>>>> case PE_OPT_MAGIC_PE32:
>>>> *width = 32;
>>>> - *image_base = base;
>>>> + *image_base = pe32_opt_hdr.pe.image_base;
>>>> + *image_size = pe32_opt_hdr.pe.image_size;
>>>> break;
>>>> case PE_OPT_MAGIC_PE32PLUS:
>>>> - *width = 64;
>>>> - *image_base = ((uint64_t)base << 32) | pe32_opt_hdr.data_base;
>>>> - break;
>>>> + if ( pe_hdr.opt_hdr_size > sizeof(pe32_opt_hdr.pep) )
>>>> + {
>>>> + if ( read(in,
>>>> + &pe32_opt_hdr.pe + 1,
>>>> + sizeof(pe32_opt_hdr.pep) - sizeof(pe32_opt_hdr.pe))
>>>> !=
>>>> + sizeof(pe32_opt_hdr.pep) - sizeof(pe32_opt_hdr.pe) )
>>>> + {
>>>> + perror(name);
>>>> + exit(3);
>>>> + }
>>>> +
>>>> + *width = 64;
>>>> + *image_base = pe32_opt_hdr.pep.image_base;
>>>> + *image_size = pe32_opt_hdr.pep.image_size;
>>>> + break;
>>>> + }
>>>
>>> Since you are already refactoring much of this code, won't it be
>>> clearer to fetch the header inside of the switch cases. So that
>>> there's a single read call for each header type?
>>
>> Except that the switch() itself uses not only pe_hdr, but also
>> pe32_opt_hdr. That could be re-arranged, but I'm a little reluctant to
>> do so.
>
> Hm, I see, the magic field checked here is in the extended header, so
> we would need to fetch it ahead of the switch in any case. How
> unhelpful.
>
> One thing that I find weird about this code is the obfuscation of the
> switch condition, won't it be easier to read as:
>
> if ( pe_hdr.magic != PE_MAGIC ||
> pe_hdr.opt_hdr_size < sizeof(pe32_opt_hdr) )
> fprintf(stderr,
> "%s: Wrong PE magic or missing optional header\n", name);
> exit(3);
> }
>
> switch ( pe32_opt_hdr.magic )
> {
> ...
>
> I would assume the current arrangement is done as to reuse the
> `default` error label, but IMO that switch condition is too hard to
> parse.
Well, yes, I have a tendency to code things like this to re-use code
where possible, but I (meanwhile) understand many people don't like
the result. Doing this differently would be a separate patch though, I
think. Anyway - to catch the maintainers' attention I guess I'll (re-)
submit the patch outside of this thread.
Jan
