On Mon, 25 Oct 2010, John Reiser wrote:
> Here's a second try [discard the first] for handling MIPS64 in recordmcount.[ch].
Thanks for your contribution -- I appreciate it as undoubtedly do the
others -- no need to feel frustrated. :)
Please note that the unusual relocation format comes from the fact the
MIPS n64 ABI supplement was developed before the ELF64 gABI was finalised
-- no surprise here given MIPS processors were the first 64-bit around.
Then the gABI took a more generic approach to handle compound relocations.
Even `readelf' you cited only got it right as recently as in 2005 (BFD was
OK from the beginning though AFAIR, so code generated as well as e.g.
`objdump' reports were right).
Your change looks good to me overall (I haven't tried building or running
it -- I take your word you've got it right). I have a small nit though --
see below.
> +typedef unsigned char myElf64_byte;
> +typedef struct {
> + Elf64_Addr r_offset; /* Address */
> + struct {
> + Elf64_Word r_sym;
> + myElf64_byte r_ssym; /* Special sym: gp-relative, etc. */
> + myElf64_byte r_type3;
> + myElf64_byte r_type2;
> + myElf64_byte r_type;
> + } r_info;
> + Elf64_Sxword r_addend; /* Addend */
> +} MIPS64_Rela;
> +
> +static uint64_t MIPS64_r_sym(Elf64_Rel const *rp)
> +{
> + return w(((MIPS64_Rela const *)rp)->r_info.r_sym);
> +}
> +
> +static void MIPS64_r_info(Elf64_Rel *const rp, unsigned sym, unsigned type)
> +{
> + MIPS64_Rela *const m64rp = (MIPS64_Rela *)rp;
> + m64rp->r_info.r_sym = w(sym);
> + m64rp->r_info.r_ssym = 0;
> + m64rp->r_info.r_type3 = 0;
> + m64rp->r_info.r_type2 = 0;
> + m64rp->r_info.r_type = type;
> +}
Please try and avoid type punning, i.e. use a union to switch between the
gABI format of r_info and the n64 MIPS psABI variation. You'll avoid the
risk of GCC doing weird stuff wrt aliasing.
Thanks,
Maciej
