drgn/libdrgn/arch_riscv.c
Omar Sandoval 14642fb3b6 libdrgn: add stub RISC-V architecture with relocation implementation
The 32-bit and 64-bit variants have different register sizes, so they're
different architectures in drgn. For now, put them in the same file so
that they can share the relocation implementation. We'll need to figure
out how to handle registers later.

P.S. RISC-V has the weirdest relocations so far. /proc/kcore also
appears to be broken.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
2022-04-19 11:51:23 -07:00

127 lines
4.0 KiB
C

// Copyright (c) Meta Platforms, Inc. and affiliates.
// SPDX-License-Identifier: GPL-3.0-or-later
#include <byteswap.h>
#include "platform.h" // IWYU pragma: associated
/*
* The ABI specification can be found at:
* https://github.com/riscv-non-isa/riscv-elf-psabi-doc
*/
static struct drgn_error drgn_invalid_rel = {
.code = DRGN_ERROR_OTHER,
.message = "invalid relocation type for SHT_REL",
};
static struct drgn_error *
apply_elf_reloc_riscv(const struct drgn_relocating_section *relocating,
uint64_t r_offset, uint32_t r_type, const int64_t *r_addend,
uint64_t sym_value)
{
switch (r_type) {
case R_RISCV_NONE:
return NULL;
case R_RISCV_32:
return drgn_reloc_add32(relocating, r_offset, r_addend,
sym_value);
case R_RISCV_64:
return drgn_reloc_add64(relocating, r_offset, r_addend,
sym_value);
#define CASE_R_RISCV_ADD_SUB(bits) \
case R_RISCV_ADD##bits: { \
if (!r_addend) \
return &drgn_invalid_rel; \
uint##bits##_t value; \
if (r_offset > relocating->buf_size || \
relocating->buf_size - r_offset < sizeof(value)) \
return &drgn_invalid_relocation_offset; \
memcpy(&value, relocating->buf + r_offset, sizeof(value)); \
if (relocating->bswap) \
value = bswap_##bits(value); \
value += sym_value + *r_addend; \
if (relocating->bswap) \
value = bswap_##bits(value); \
memcpy(relocating->buf + r_offset, &value, sizeof(value)); \
return NULL; \
} \
case R_RISCV_SUB##bits: { \
if (!r_addend) \
return &drgn_invalid_rel; \
uint##bits##_t value; \
if (r_offset > relocating->buf_size || \
relocating->buf_size - r_offset < sizeof(value)) \
return &drgn_invalid_relocation_offset; \
memcpy(&value, relocating->buf + r_offset, sizeof(value)); \
if (relocating->bswap) \
value = bswap_##bits(value); \
value -= sym_value + *r_addend; \
if (relocating->bswap) \
value = bswap_##bits(value); \
memcpy(relocating->buf + r_offset, &value, sizeof(value)); \
return NULL; \
}
#define bswap_8(x) (x)
CASE_R_RISCV_ADD_SUB(8)
#undef bswap_8
CASE_R_RISCV_ADD_SUB(16)
CASE_R_RISCV_ADD_SUB(32)
CASE_R_RISCV_ADD_SUB(64)
#undef CASE_R_RISCV_ADD_SUB
case R_RISCV_SUB6: {
if (!r_addend)
return &drgn_invalid_rel;
uint8_t value;
if (r_offset > relocating->buf_size ||
relocating->buf_size - r_offset < sizeof(value))
return &drgn_invalid_relocation_offset;
memcpy(&value, relocating->buf + r_offset, sizeof(value));
value = ((value & 0xc0) |
(((value & 0x3f) - (sym_value + *r_addend)) & 0x3f));
memcpy(relocating->buf + r_offset, &value, sizeof(value));
return NULL;
}
case R_RISCV_SET6: {
if (!r_addend)
return &drgn_invalid_rel;
uint8_t value;
if (r_offset > relocating->buf_size ||
relocating->buf_size - r_offset < sizeof(value))
return &drgn_invalid_relocation_offset;
memcpy(&value, relocating->buf + r_offset, sizeof(value));
value = (value & 0xc0) | ((sym_value + *r_addend) & 0x3f);
memcpy(relocating->buf + r_offset, &value, sizeof(value));
return NULL;
}
case R_RISCV_SET8:
return drgn_reloc_add8(relocating, r_offset, r_addend,
sym_value);
case R_RISCV_SET16:
return drgn_reloc_add16(relocating, r_offset, r_addend,
sym_value);
case R_RISCV_SET32:
return drgn_reloc_add32(relocating, r_offset, r_addend,
sym_value);
default:
return DRGN_UNKNOWN_RELOCATION_TYPE(r_type);
}
}
const struct drgn_architecture_info arch_info_riscv64 = {
.name = "RISC-V 64",
.arch = DRGN_ARCH_RISCV64,
.default_flags = (DRGN_PLATFORM_IS_64_BIT |
DRGN_PLATFORM_IS_LITTLE_ENDIAN),
.register_by_name = drgn_register_by_name_unknown,
.apply_elf_reloc = apply_elf_reloc_riscv,
};
const struct drgn_architecture_info arch_info_riscv32 = {
.name = "RISC-V 32",
.arch = DRGN_ARCH_RISCV32,
.default_flags = DRGN_PLATFORM_IS_LITTLE_ENDIAN,
.register_by_name = drgn_register_by_name_unknown,
.apply_elf_reloc = apply_elf_reloc_riscv,
};