omjavaid added a comment.
In D92063#2416162 <https://reviews.llvm.org/D92063#2416162>, @labath wrote:
> +@mgorny, as he's been navigating these waters lately...
>
> So... I presume we can't just slap `__attribute__((packed))` on the
> structure, because the kernel actually expects that the data structure will
> have the extra space for the padding. Is that so?
>
> Even if we can't, I'm wondering if it wouldn't be cleaner to use two
> structures for this. Something like:
>
> LLVM_PACKED_START
> struct GPR {
> // as before...
> };
> /// Big comment explaining the purpose of padding
> struct GPRBuffer: GPR {
> uint32_t pad;
> };
> LLVM_PACKED_END
>
> and then using GPR or GPRBuffer accordingly. What do you think?
So I didnt check this before but FreeBSD and Linux have different ptrace GPR
size expectation. Here is what FreeBSD struct looks like:
struct reg {
uint64_t x[30];
uint64_t lr;
uint64_t sp;
uint64_t elr;
uint32_t spsr;
};
While on Linux it looks something like this:
struct {
u64 regs[31];
u64 sp;
u64 pc;
u64 pstate;
};
So I am going to put a __attribute__((packed)) and use the same for FreeBSD
while going to isolate Linux implementation in my next update.
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D92063/new/
https://reviews.llvm.org/D92063
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