[PATCH] RISC-V: Add support for vendor-specific relocations

[Nelson Chu]

On Wed, Apr 9, 2025 at 4:59 PM Alexey Lapshin <alexey.lapshin@espressif.com>
wrote:

> +struct elf_vendor_map
> +{
> +  enum elf_riscv_vendor_id id;
> +  const char *id_str;
> +};
> +
> +static const struct elf_vendor_map elf_riscv_vendor_map[] =
> +{
> +  { R_RISCV_VENDOR_ID_ESP, R_RISCV_ESPRESSIF_VENDOR_ID_STR },
> +};
> +
> +enum elf_riscv_vendor_id
> +riscv_elf_vendor_id_str_to_enum(const char *id_str)
> +{
> +  unsigned int i;
> +  for (i = 0; i < ARRAY_SIZE (elf_riscv_vendor_map); i++)
> +    if (strcmp(elf_riscv_vendor_map[i].id_str, id_str) == 0)
> +      return elf_riscv_vendor_map[i].id;
> +
> +  return R_RISCV_VENDOR_ID_NONE;
> +}
> +
> +struct elf_reloc_map_esp
> +{
> +  bfd_reloc_code_real_type bfd_val;
> +  enum elf_riscv_esp_reloc_type elf_val;
> +};
> +
> +static const struct elf_reloc_map_esp riscv_esp_reloc_map[] =
> +{
> +  { BFD_RELOC_RISCV_ESP_LP_OFFSET_9, R_RISCV_ESP_LP_OFFSET_9 },
> +  { BFD_RELOC_RISCV_ESP_LP_OFFSET_12, R_RISCV_ESP_LP_OFFSET_12 },
> +};
>

I forgot to mention this - could we just define these vendor mappings into
elf_riscv_map, so...


> diff --git a/include/elf/riscv.h b/include/elf/riscv.h
> index 2ea1ae82eb6..0f3a5c4ded6 100644
> --- a/include/elf/riscv.h
> +++ b/include/elf/riscv.h
> +
> +/* Vendor specific relocations macro and structures.  */
> +#define R_RISCV_ESPRESSIF_VENDOR_ID_STR "esp"
> +
> +/* VENDOR IDs for internal usage.  */
> +enum elf_riscv_vendor_id {
> +  R_RISCV_VENDOR_ID_NONE = -1,
> +  R_RISCV_VENDOR_ID_ESP,
> +};
> +
> +/* Vendor (Espressif) relocations.  */
> +START_RELOC_NUMBERS (elf_riscv_esp_reloc_type)
> +  RELOC_NUMBER (R_RISCV_ESP_LP_OFFSET_9, 192)
> +  RELOC_NUMBER (R_RISCV_ESP_LP_OFFSET_12, 193)
> +END_RELOC_NUMBERS (R_RISCV_ESP_max)
>

...  We probably don't need to define so many elf_riscv_xxx_reloc_type for
every vendor.  I see MIPS and ARM had defined FAKE_RELOC for
duplicate cases, not sure if that also works for risc-v vendor
relocations.  That is - could we define FAKE_RELOC (R_RISCV_vendor_begin)
and FAKE_RELOC (R_RISCV_vendor_end), then define all vendor stuff between
them?

Thanks
Nelson
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