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-rw-r--r--arch/arm/kernel/module.c168
1 files changed, 130 insertions, 38 deletions
diff --git a/arch/arm/kernel/module.c b/arch/arm/kernel/module.c
index beac45e89ba6..d59c36dc0494 100644
--- a/arch/arm/kernel/module.c
+++ b/arch/arm/kernel/module.c
@@ -68,6 +68,44 @@ bool module_exit_section(const char *name)
strstarts(name, ".ARM.exidx.exit");
}
+#ifdef CONFIG_ARM_HAS_GROUP_RELOCS
+/*
+ * This implements the partitioning algorithm for group relocations as
+ * documented in the ARM AArch32 ELF psABI (IHI 0044).
+ *
+ * A single PC-relative symbol reference is divided in up to 3 add or subtract
+ * operations, where the final one could be incorporated into a load/store
+ * instruction with immediate offset. E.g.,
+ *
+ * ADD Rd, PC, #... or ADD Rd, PC, #...
+ * ADD Rd, Rd, #... ADD Rd, Rd, #...
+ * LDR Rd, [Rd, #...] ADD Rd, Rd, #...
+ *
+ * The latter has a guaranteed range of only 16 MiB (3x8 == 24 bits), so it is
+ * of limited use in the kernel. However, the ADD/ADD/LDR combo has a range of
+ * -/+ 256 MiB, (2x8 + 12 == 28 bits), which means it has sufficient range for
+ * any in-kernel symbol reference (unless module PLTs are being used).
+ *
+ * The main advantage of this approach over the typical pattern using a literal
+ * load is that literal loads may miss in the D-cache, and generally lead to
+ * lower cache efficiency for variables that are referenced often from many
+ * different places in the code.
+ */
+static u32 get_group_rem(u32 group, u32 *offset)
+{
+ u32 val = *offset;
+ u32 shift;
+ do {
+ shift = val ? (31 - __fls(val)) & ~1 : 32;
+ *offset = val;
+ if (!val)
+ break;
+ val &= 0xffffff >> shift;
+ } while (group--);
+ return shift;
+}
+#endif
+
int
apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
unsigned int relindex, struct module *module)
@@ -82,6 +120,9 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
unsigned long loc;
Elf32_Sym *sym;
const char *symname;
+#ifdef CONFIG_ARM_HAS_GROUP_RELOCS
+ u32 shift, group = 1;
+#endif
s32 offset;
u32 tmp;
#ifdef CONFIG_THUMB2_KERNEL
@@ -212,6 +253,55 @@ apply_relocate(Elf32_Shdr *sechdrs, const char *strtab, unsigned int symindex,
*(u32 *)loc = __opcode_to_mem_arm(tmp);
break;
+#ifdef CONFIG_ARM_HAS_GROUP_RELOCS
+ case R_ARM_ALU_PC_G0_NC:
+ group = 0;
+ fallthrough;
+ case R_ARM_ALU_PC_G1_NC:
+ tmp = __mem_to_opcode_arm(*(u32 *)loc);
+ offset = ror32(tmp & 0xff, (tmp & 0xf00) >> 7);
+ if (tmp & BIT(22))
+ offset = -offset;
+ offset += sym->st_value - loc;
+ if (offset < 0) {
+ offset = -offset;
+ tmp = (tmp & ~BIT(23)) | BIT(22); // SUB opcode
+ } else {
+ tmp = (tmp & ~BIT(22)) | BIT(23); // ADD opcode
+ }
+
+ shift = get_group_rem(group, &offset);
+ if (shift < 24) {
+ offset >>= 24 - shift;
+ offset |= (shift + 8) << 7;
+ }
+ *(u32 *)loc = __opcode_to_mem_arm((tmp & ~0xfff) | offset);
+ break;
+
+ case R_ARM_LDR_PC_G2:
+ tmp = __mem_to_opcode_arm(*(u32 *)loc);
+ offset = tmp & 0xfff;
+ if (~tmp & BIT(23)) // U bit cleared?
+ offset = -offset;
+ offset += sym->st_value - loc;
+ if (offset < 0) {
+ offset = -offset;
+ tmp &= ~BIT(23); // clear U bit
+ } else {
+ tmp |= BIT(23); // set U bit
+ }
+ get_group_rem(2, &offset);
+
+ if (offset > 0xfff) {
+ pr_err("%s: section %u reloc %u sym '%s': relocation %u out of range (%#lx -> %#x)\n",
+ module->name, relindex, i, symname,
+ ELF32_R_TYPE(rel->r_info), loc,
+ sym->st_value);
+ return -ENOEXEC;
+ }
+ *(u32 *)loc = __opcode_to_mem_arm((tmp & ~0xfff) | offset);
+ break;
+#endif
#ifdef CONFIG_THUMB2_KERNEL
case R_ARM_THM_CALL:
case R_ARM_THM_JUMP24:
@@ -369,46 +459,40 @@ int module_finalize(const Elf32_Ehdr *hdr, const Elf_Shdr *sechdrs,
#ifdef CONFIG_ARM_UNWIND
const char *secstrs = (void *)hdr + sechdrs[hdr->e_shstrndx].sh_offset;
const Elf_Shdr *sechdrs_end = sechdrs + hdr->e_shnum;
- struct mod_unwind_map maps[ARM_SEC_MAX];
- int i;
+ struct list_head *unwind_list = &mod->arch.unwind_list;
- memset(maps, 0, sizeof(maps));
+ INIT_LIST_HEAD(unwind_list);
+ mod->arch.init_table = NULL;
for (s = sechdrs; s < sechdrs_end; s++) {
const char *secname = secstrs + s->sh_name;
+ const char *txtname;
+ const Elf_Shdr *txt_sec;
- if (!(s->sh_flags & SHF_ALLOC))
+ if (!(s->sh_flags & SHF_ALLOC) ||
+ s->sh_type != ELF_SECTION_UNWIND)
continue;
- if (strcmp(".ARM.exidx.init.text", secname) == 0)
- maps[ARM_SEC_INIT].unw_sec = s;
- else if (strcmp(".ARM.exidx", secname) == 0)
- maps[ARM_SEC_CORE].unw_sec = s;
- else if (strcmp(".ARM.exidx.exit.text", secname) == 0)
- maps[ARM_SEC_EXIT].unw_sec = s;
- else if (strcmp(".ARM.exidx.text.unlikely", secname) == 0)
- maps[ARM_SEC_UNLIKELY].unw_sec = s;
- else if (strcmp(".ARM.exidx.text.hot", secname) == 0)
- maps[ARM_SEC_HOT].unw_sec = s;
- else if (strcmp(".init.text", secname) == 0)
- maps[ARM_SEC_INIT].txt_sec = s;
- else if (strcmp(".text", secname) == 0)
- maps[ARM_SEC_CORE].txt_sec = s;
- else if (strcmp(".exit.text", secname) == 0)
- maps[ARM_SEC_EXIT].txt_sec = s;
- else if (strcmp(".text.unlikely", secname) == 0)
- maps[ARM_SEC_UNLIKELY].txt_sec = s;
- else if (strcmp(".text.hot", secname) == 0)
- maps[ARM_SEC_HOT].txt_sec = s;
- }
+ if (!strcmp(".ARM.exidx", secname))
+ txtname = ".text";
+ else
+ txtname = secname + strlen(".ARM.exidx");
+ txt_sec = find_mod_section(hdr, sechdrs, txtname);
+
+ if (txt_sec) {
+ struct unwind_table *table =
+ unwind_table_add(s->sh_addr,
+ s->sh_size,
+ txt_sec->sh_addr,
+ txt_sec->sh_size);
+
+ list_add(&table->mod_list, unwind_list);
- for (i = 0; i < ARM_SEC_MAX; i++)
- if (maps[i].unw_sec && maps[i].txt_sec)
- mod->arch.unwind[i] =
- unwind_table_add(maps[i].unw_sec->sh_addr,
- maps[i].unw_sec->sh_size,
- maps[i].txt_sec->sh_addr,
- maps[i].txt_sec->sh_size);
+ /* save init table for module_arch_freeing_init */
+ if (strcmp(".ARM.exidx.init.text", secname) == 0)
+ mod->arch.init_table = table;
+ }
+ }
#endif
#ifdef CONFIG_ARM_PATCH_PHYS_VIRT
s = find_mod_section(hdr, sechdrs, ".pv_table");
@@ -429,19 +513,27 @@ void
module_arch_cleanup(struct module *mod)
{
#ifdef CONFIG_ARM_UNWIND
- int i;
+ struct unwind_table *tmp;
+ struct unwind_table *n;
- for (i = 0; i < ARM_SEC_MAX; i++) {
- unwind_table_del(mod->arch.unwind[i]);
- mod->arch.unwind[i] = NULL;
+ list_for_each_entry_safe(tmp, n,
+ &mod->arch.unwind_list, mod_list) {
+ list_del(&tmp->mod_list);
+ unwind_table_del(tmp);
}
+ mod->arch.init_table = NULL;
#endif
}
void __weak module_arch_freeing_init(struct module *mod)
{
#ifdef CONFIG_ARM_UNWIND
- unwind_table_del(mod->arch.unwind[ARM_SEC_INIT]);
- mod->arch.unwind[ARM_SEC_INIT] = NULL;
+ struct unwind_table *init = mod->arch.init_table;
+
+ if (init) {
+ mod->arch.init_table = NULL;
+ list_del(&init->mod_list);
+ unwind_table_del(init);
+ }
#endif
}
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.