[PATCH v8 07/13] powerpc: Adapt elf64_apply_relocate_add for kexec_file_load.

Thiago Jung Bauermann
2016-09-05T22:22:22Z

Extend elf64_apply_relocate_add to support relative symbols. This is
necessary because there is a difference between how the module loading
mechanism and the kexec purgatory loading code use Elf64_Sym.st_value
at relocation time: the former changes st_value to point to the absolute
memory address before relocating the module, while the latter does that
adjustment during relocation of the purgatory.

Also, add a check_symbols argument so that the kexec code can be stricter
about undefined symbols.

Finally, add relocation types used by the purgatory.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
arch/powerpc/include/asm/elf_util.h | 2 +
arch/powerpc/kernel/elf_util_64.c | 100 +++++++++++++++++++++++++++++++++---
arch/powerpc/kernel/module_64.c | 6 ++-
3 files changed, 99 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/include/asm/elf_util.h b/arch/powerpc/include/asm/elf_util.h
index a012ba03282d..5a27e8ceb88a 100644
--- a/arch/powerpc/include/asm/elf_util.h
+++ b/arch/powerpc/include/asm/elf_util.h
@@ -20,6 +20,7 @@
#include <linux/elf.h>

struct elf_info {
+ const struct elfhdr *ehdr;
struct elf_shdr *sechdrs;

/* Index of stubs section. */
@@ -67,6 +68,7 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
const char *strtab, const Elf64_Rela *rela,
unsigned int num_rela, void *syms_base,
void *loc_base, Elf64_Addr addr_base,
+ bool relative_symbols, bool check_symbols,
const char *obj_name);

#endif /* _ASM_POWERPC_ELF_UTIL_H */
diff --git a/arch/powerpc/kernel/elf_util_64.c b/arch/powerpc/kernel/elf_util_64.c
index 8e5d400ac9f2..1b17df71fb8d 100644
--- a/arch/powerpc/kernel/elf_util_64.c
+++ b/arch/powerpc/kernel/elf_util_64.c
@@ -74,6 +74,8 @@ static void squash_toc_save_inst(const char *name, unsigned long addr) { }
* @syms_base: Contents of the associated symbol table.
* @loc_base: Contents of the section to which relocations apply.
* @addr_base: The address where the section will be loaded in memory.
+ * @relative_symbols: Are the symbols' st_value members relative?
+ * @check_symbols: Fail if an unexpected symbol is found?
* @obj_name: The name of the ELF binary, for information messages.
*
* Applies RELA relocations to an ELF file already at its final location
@@ -84,12 +86,15 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
const char *strtab, const Elf64_Rela *rela,
unsigned int num_rela, void *syms_base,
void *loc_base, Elf64_Addr addr_base,
+ bool relative_symbols, bool check_symbols,
const char *obj_name)
{
unsigned int i;
unsigned long *location;
unsigned long address;
+ unsigned long sec_base;
unsigned long value;
+ int reloc_type;
const char *name;
Elf64_Sym *sym;

@@ -116,15 +121,44 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
else
name = "<unnamed symbol>";

- pr_debug("RELOC at %p: %li-type as %s (0x%lx) + %li\n",
- location, (long)ELF64_R_TYPE(rela[i].r_info),
- name, (unsigned long)sym->st_value,
+ reloc_type = ELF64_R_TYPE(rela[i].r_info);
+
+ pr_debug("RELOC at %p: %i-type as %s (0x%lx) + %li\n",
+ location, reloc_type, name, (unsigned long)sym->st_value,
(long)rela[i].r_addend);

+ if (check_symbols) {
+ /*
+ * TOC symbols appear as undefined but should be
+ * resolved as well, so allow them to be processed.
+ */
+ if (sym->st_shndx == SHN_UNDEF &&
+ strcmp(name, ".TOC.") != 0 &&
+ reloc_type != R_PPC64_TOC) {
+ pr_err("Undefined symbol: %s\n", name);
+ return -ENOEXEC;
+ } else if (sym->st_shndx == SHN_COMMON) {
+ pr_err("Symbol '%s' in common section.\n",
+ name);
+ return -ENOEXEC;
+ }
+ }
+
+ if (relative_symbols && sym->st_shndx != SHN_ABS) {
+ if (sym->st_shndx >= elf_info->ehdr->e_shnum) {
+ pr_err("Invalid section %d for symbol %s\n",
+ sym->st_shndx, name);
+ return -ENOEXEC;
+ }
+
+ sec_base = elf_info->sechdrs[sym->st_shndx].sh_addr;
+ } else
+ sec_base = 0;
+
/* `Everything is relative'. */
- value = sym->st_value + rela[i].r_addend;
+ value = sym->st_value + sec_base + rela[i].r_addend;

- switch (ELF64_R_TYPE(rela[i].r_info)) {
+ switch (reloc_type) {
case R_PPC64_ADDR32:
/* Simply set it */
*(u32 *)location = value;
@@ -135,6 +169,11 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
*(unsigned long *)location = value;
break;

+ case R_PPC64_REL32:
+ *(uint32_t *) location =
+ value - (uint32_t)(uint64_t) location;
+ break;
+
case R_PPC64_TOC:
*(unsigned long *)location = my_r2(elf_info);
break;
@@ -186,6 +225,14 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
| (value & 0xfffc);
break;

+ case R_PPC64_TOC16_HI:
+ /* Subtract TOC pointer */
+ value -= my_r2(elf_info);
+ value = value >> 16;
+ *((uint16_t *) location)
+ = (*((uint16_t *) location) & ~0xffff)
+ | (value & 0xffff);
+
case R_PPC64_TOC16_HA:
/* Subtract TOC pointer */
value -= my_r2(elf_info);
@@ -195,6 +242,21 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
| (value & 0xffff);
break;

+ case R_PPC64_REL14:
+ /* Convert value to relative */
+ value -= address;
+ if (value + 0x8000 > 0xffff || (value & 3) != 0) {
+ pr_err("%s: REL14 %li out of range!\n",
+ obj_name, (long int) value);
+ return -ENOEXEC;
+ }
+
+ /* Only replace bits 2 through 16 */
+ *(uint32_t *)location
+ = (*(uint32_t *)location & ~0xfffc)
+ | (value & 0xfffc);
+ break;
+
case R_PPC_REL24:
/* FIXME: Handle weak symbols here --RR */
if (sym->st_shndx == SHN_UNDEF) {
@@ -263,6 +325,29 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
((uint32_t *)location)[1] = 0x38420000 + PPC_LO(value);
break;

+ case R_PPC64_ADDR16_LO:
+ *(uint16_t *)location = value & 0xffff;
+ break;
+
+ case R_PPC64_ADDR16_HI:
+ *(uint16_t *)location = (value >> 16) & 0xffff;
+ break;
+
+ case R_PPC64_ADDR16_HA:
+ *(uint16_t *)location = (((value + 0x8000) >> 16) &
+ 0xffff);
+ break;
+
+ case R_PPC64_ADDR16_HIGHER:
+ *(uint16_t *)location = (((uint64_t)value >> 32) &
+ 0xffff);
+ break;
+
+ case R_PPC64_ADDR16_HIGHEST:
+ *(uint16_t *)location = (((uint64_t)value >> 48) &
+ 0xffff);
+ break;
+
case R_PPC64_REL16_HA:
/* Subtract location pointer */
value -= address;
@@ -281,9 +366,8 @@ int elf64_apply_relocate_add(const struct elf_info *elf_info,
break;

default:
- pr_err("%s: Unknown ADD relocation: %lu\n",
- obj_name,
- (unsigned long)ELF64_R_TYPE(rela[i].r_info));
+ pr_err("%s: Unknown ADD relocation: %d\n", obj_name,
+ reloc_type);
return -ENOEXEC;
}
}
diff --git a/arch/powerpc/kernel/module_64.c b/arch/powerpc/kernel/module_64.c
index 590e2413974f..ff9ab8194188 100644
--- a/arch/powerpc/kernel/module_64.c
+++ b/arch/powerpc/kernel/module_64.c
@@ -341,6 +341,7 @@ int module_frob_arch_sections(Elf64_Ehdr *hdr,
sechdrs[me->arch.elf_info.stubs_section].sh_size = get_stubs_size(hdr, sechdrs);

/* For the elf_util functions. */
+ me->arch.elf_info.ehdr = hdr;
me->arch.elf_info.sechdrs = sechdrs;

return 0;
@@ -443,6 +444,9 @@ int restore_r2(u32 *instruction, const char *obj_name)
* When this function is called, the module is already at its final location in
* memory, so Elf64_Shdr.sh_addr can be used for accessing the section
* contents as well as the base address for relocations.
+ *
+ * Also, simplify_symbols already changed all symbols' st_value members
+ * to absolute addresses.
*/
int apply_relocate_add(Elf64_Shdr *sechdrs,
const char *strtab,
@@ -472,7 +476,7 @@ int apply_relocate_add(Elf64_Shdr *sechdrs,

return elf64_apply_relocate_add(&me->arch.elf_info, strtab, rela,
num_rela, syms_base, (void *) addr_base,
- addr_base, me->name);
+ addr_base, false, false, me->name);
}

#ifdef CONFIG_DYNAMIC_FTRACE
--
1.9.1