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riscv: kexec: fix purgatory PC-relative relocation pairing #43

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riscv: kexec: fix purgatory PC-relative relocation pairing #43

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66 changes: 58 additions & 8 deletions arch/riscv/kernel/machine_kexec_file.c
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
#include <linux/of.h>
#include <linux/libfdt.h>
#include <linux/types.h>
#include <linux/unaligned.h>
#include <linux/memblock.h>
#include <linux/vmalloc.h>
#include <asm/setup.h>
Expand Down Expand Up @@ -118,6 +119,8 @@ static char *setup_kdump_cmdline(struct kimage *image, char *cmdline,

#define ENCODE_ITYPE_IMM(x) \
(RV_X(x, 0, 12) << 20)
#define ENCODE_STYPE_IMM(x) \
((RV_X(x, 0, 5) << 7) | (RV_X(x, 5, 7) << 25))
#define ENCODE_BTYPE_IMM(x) \
((RV_X(x, 1, 4) << 8) | (RV_X(x, 5, 6) << 25) | \
(RV_X(x, 11, 1) << 7) | (RV_X(x, 12, 1) << 31))
Expand Down Expand Up @@ -164,6 +167,7 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
unsigned long addr; /* final location after relocation */
unsigned long val; /* relocated symbol value */
unsigned long sec_base; /* relocated symbol value */
long offset;
void *loc; /* tmp location to modify */

sym = (void *)pi->ehdr + symtab->sh_offset;
Expand Down Expand Up @@ -204,13 +208,61 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
*(u32 *)loc = CLEAN_IMM(JTYPE, *(u32 *)loc) |
ENCODE_JTYPE_IMM(val - addr);
break;
/*
* With no R_RISCV_PCREL_LO12_S, R_RISCV_PCREL_LO12_I
* sym is expected to be next to R_RISCV_PCREL_HI20
* in purgatory relsec. Handle it like R_RISCV_CALL
* sym, instead of searching the whole relsec.
*/
case R_RISCV_PCREL_HI20:
offset = val - addr;
/* AUIPC plus a signed 12-bit immediate. */
if (offset < -(1L << 31) - (1L << 11) ||
offset >= (1L << 31) - (1L << 11)) {
pr_err("PCREL_HI20 offset out of range\n");
return -ENOEXEC;
}
put_unaligned_le32(CLEAN_IMM(UTYPE, get_unaligned_le32(loc)) |
ENCODE_UTYPE_IMM(RISCV_CONST_HIGH_PART(offset)), loc);
break;
case R_RISCV_PCREL_LO12_I:
case R_RISCV_PCREL_LO12_S: {
const Elf64_Rela *hi = NULL;
const Elf_Sym *hi_sym;
unsigned int j;

/* The low relocation names the HI instruction, not its target. */
if (sym->st_shndx != relsec->sh_info || relas[i].r_addend)
return -ENOEXEC;

/*
* Instructions and relocation records need not be adjacent or
* ordered. Multiple low relocations may reference the same HI.
* ponytail: small built-in table; index HI offsets if it grows.
*/
for (j = 0; j < relsec->sh_size / sizeof(*relas); j++) {
if (ELF64_R_TYPE(relas[j].r_info) == R_RISCV_PCREL_HI20 &&
relas[j].r_offset == sym->st_value) {
hi = &relas[j];
break;
}
}
if (!hi || ELF64_R_SYM(hi->r_info) >= symtab->sh_size / sizeof(*sym)) {
pr_err("Missing PCREL_HI20 relocation or symbol\n");
return -ENOEXEC;
}
hi_sym = (void *)pi->ehdr + symtab->sh_offset;
hi_sym += ELF64_R_SYM(hi->r_info);
sec_base = 0;
if (hi_sym->st_shndx != SHN_ABS) {
if (hi_sym->st_shndx >= pi->ehdr->e_shnum)
return -ENOEXEC;
sec_base = pi->sechdrs[hi_sym->st_shndx].sh_addr;
}
val = hi_sym->st_value + sec_base + hi->r_addend -
(section->sh_addr + hi->r_offset);
if (r_type == R_RISCV_PCREL_LO12_I)
put_unaligned_le32(CLEAN_IMM(ITYPE, get_unaligned_le32(loc)) |
ENCODE_ITYPE_IMM(val), loc);
else
put_unaligned_le32(CLEAN_IMM(STYPE, get_unaligned_le32(loc)) |
ENCODE_STYPE_IMM(val), loc);
break;
}
case R_RISCV_CALL_PLT:
case R_RISCV_CALL:
*(u64 *)loc = CLEAN_IMM(UITYPE, *(u64 *)loc) |
Expand All @@ -236,8 +288,6 @@ int arch_kexec_apply_relocations_add(struct purgatory_info *pi,
case R_RISCV_SUB32:
*(u32 *)loc -= val;
break;
/* It has been applied by R_RISCV_PCREL_HI20 sym */
case R_RISCV_PCREL_LO12_I:
case R_RISCV_ALIGN:
case R_RISCV_RELAX:
break;
Expand Down