On Mon, Sep 19, 2022, Ricardo Koller wrote:
> On Sat, Sep 17, 2022 at 09:58:28PM +0000, Oliver Upton wrote:
> > @@ -536,13 +536,7 @@ static void load_exec_code_for_test(struct kvm_vm *vm)
> > assert(TEST_EXEC_GVA - TEST_GVA);
> > code = hva + 8;
> >
> > - /*
> > - * We need the cast to be separate in order for the compiler to not
> > - * complain with: "‘memcpy’ forming offset [1, 7] is out of the bounds
> > - * [0, 1] of object ‘__exec_test’ with type ‘unsigned char’"
> > - */
> > - c = (uint64_t *)&__exec_test;
> > - memcpy(code, c, 8);
> > + *code = __exec_test;
>
> I remember trying many ways of getting the compiler to not complain, I
> must have tried this (wonder what happened). Anyway, gcc and clang are
> happy with it.
Alternatively, from a code documentation perspective it would be nice to capture
that the size isn't arbitrary. E.g.
typedef uint32_t aarch64_insn_t;
extern aarch64_insn_t __exec_test[2];
{
void *code;
memcpy(code, __exec_test, sizeof(__exec_test));
}
Note, memcpy() is currently dangerous, but hopefully that will be remedied soonish[*]
[*] https://lore.kernel.org/all/20220908233134.3523339-1-seanjc@xxxxxxxxxx
