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authorVivek Goyal <vgoyal@redhat.com>2014-08-08 14:26:04 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-08-08 15:57:32 -0700
commit12db5562e0352986a265841638482b84f3a6899b (patch)
tree533100da8331131037128616b3f9d501c07a6def /arch/x86
parent8fc5b4d4121c95482b2583a07863c6b0aba2d9e1 (diff)
downloadlinux-12db5562e0352986a265841638482b84f3a6899b.tar.gz
kexec: load and relocate purgatory at kernel load time
Load purgatory code in RAM and relocate it based on the location. Relocation code has been inspired by module relocation code and purgatory relocation code in kexec-tools. Also compute the checksums of loaded kexec segments and store them in purgatory. Arch independent code provides this functionality so that arch dependent bootloaders can make use of it. Helper functions are provided to get/set symbol values in purgatory which are used by bootloaders later to set things like stack and entry point of second kernel etc. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Cc: Borislav Petkov <bp@suse.de> Cc: Michael Kerrisk <mtk.manpages@gmail.com> Cc: Yinghai Lu <yinghai@kernel.org> Cc: Eric Biederman <ebiederm@xmission.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Matthew Garrett <mjg59@srcf.ucam.org> Cc: Greg Kroah-Hartman <greg@kroah.com> Cc: Dave Young <dyoung@redhat.com> Cc: WANG Chao <chaowang@redhat.com> Cc: Baoquan He <bhe@redhat.com> Cc: Andy Lutomirski <luto@amacapital.net> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/x86')
-rw-r--r--arch/x86/Kconfig2
-rw-r--r--arch/x86/kernel/machine_kexec_64.c142
2 files changed, 144 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 98fe3df6df8..9558b9fcafb 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1583,6 +1583,8 @@ source kernel/Kconfig.hz
config KEXEC
bool "kexec system call"
select BUILD_BIN2C
+ select CRYPTO
+ select CRYPTO_SHA256
---help---
kexec is a system call that implements the ability to shutdown your
current kernel, and to start another kernel. It is like a reboot
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index c8875b5545e..88404c44072 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -6,6 +6,8 @@
* Version 2. See the file COPYING for more details.
*/
+#define pr_fmt(fmt) "kexec: " fmt
+
#include <linux/mm.h>
#include <linux/kexec.h>
#include <linux/string.h>
@@ -328,3 +330,143 @@ int arch_kimage_file_post_load_cleanup(struct kimage *image)
return image->fops->cleanup(image);
}
+
+/*
+ * Apply purgatory relocations.
+ *
+ * ehdr: Pointer to elf headers
+ * sechdrs: Pointer to section headers.
+ * relsec: section index of SHT_RELA section.
+ *
+ * TODO: Some of the code belongs to generic code. Move that in kexec.c.
+ */
+int arch_kexec_apply_relocations_add(const Elf64_Ehdr *ehdr,
+ Elf64_Shdr *sechdrs, unsigned int relsec)
+{
+ unsigned int i;
+ Elf64_Rela *rel;
+ Elf64_Sym *sym;
+ void *location;
+ Elf64_Shdr *section, *symtabsec;
+ unsigned long address, sec_base, value;
+ const char *strtab, *name, *shstrtab;
+
+ /*
+ * ->sh_offset has been modified to keep the pointer to section
+ * contents in memory
+ */
+ rel = (void *)sechdrs[relsec].sh_offset;
+
+ /* Section to which relocations apply */
+ section = &sechdrs[sechdrs[relsec].sh_info];
+
+ pr_debug("Applying relocate section %u to %u\n", relsec,
+ sechdrs[relsec].sh_info);
+
+ /* Associated symbol table */
+ symtabsec = &sechdrs[sechdrs[relsec].sh_link];
+
+ /* String table */
+ if (symtabsec->sh_link >= ehdr->e_shnum) {
+ /* Invalid strtab section number */
+ pr_err("Invalid string table section index %d\n",
+ symtabsec->sh_link);
+ return -ENOEXEC;
+ }
+
+ strtab = (char *)sechdrs[symtabsec->sh_link].sh_offset;
+
+ /* section header string table */
+ shstrtab = (char *)sechdrs[ehdr->e_shstrndx].sh_offset;
+
+ for (i = 0; i < sechdrs[relsec].sh_size / sizeof(*rel); i++) {
+
+ /*
+ * rel[i].r_offset contains byte offset from beginning
+ * of section to the storage unit affected.
+ *
+ * This is location to update (->sh_offset). This is temporary
+ * buffer where section is currently loaded. This will finally
+ * be loaded to a different address later, pointed to by
+ * ->sh_addr. kexec takes care of moving it
+ * (kexec_load_segment()).
+ */
+ location = (void *)(section->sh_offset + rel[i].r_offset);
+
+ /* Final address of the location */
+ address = section->sh_addr + rel[i].r_offset;
+
+ /*
+ * rel[i].r_info contains information about symbol table index
+ * w.r.t which relocation must be made and type of relocation
+ * to apply. ELF64_R_SYM() and ELF64_R_TYPE() macros get
+ * these respectively.
+ */
+ sym = (Elf64_Sym *)symtabsec->sh_offset +
+ ELF64_R_SYM(rel[i].r_info);
+
+ if (sym->st_name)
+ name = strtab + sym->st_name;
+ else
+ name = shstrtab + sechdrs[sym->st_shndx].sh_name;
+
+ pr_debug("Symbol: %s info: %02x shndx: %02x value=%llx size: %llx\n",
+ name, sym->st_info, sym->st_shndx, sym->st_value,
+ sym->st_size);
+
+ if (sym->st_shndx == SHN_UNDEF) {
+ pr_err("Undefined symbol: %s\n", name);
+ return -ENOEXEC;
+ }
+
+ if (sym->st_shndx == SHN_COMMON) {
+ pr_err("symbol '%s' in common section\n", name);
+ return -ENOEXEC;
+ }
+
+ if (sym->st_shndx == SHN_ABS)
+ sec_base = 0;
+ else if (sym->st_shndx >= ehdr->e_shnum) {
+ pr_err("Invalid section %d for symbol %s\n",
+ sym->st_shndx, name);
+ return -ENOEXEC;
+ } else
+ sec_base = sechdrs[sym->st_shndx].sh_addr;
+
+ value = sym->st_value;
+ value += sec_base;
+ value += rel[i].r_addend;
+
+ switch (ELF64_R_TYPE(rel[i].r_info)) {
+ case R_X86_64_NONE:
+ break;
+ case R_X86_64_64:
+ *(u64 *)location = value;
+ break;
+ case R_X86_64_32:
+ *(u32 *)location = value;
+ if (value != *(u32 *)location)
+ goto overflow;
+ break;
+ case R_X86_64_32S:
+ *(s32 *)location = value;
+ if ((s64)value != *(s32 *)location)
+ goto overflow;
+ break;
+ case R_X86_64_PC32:
+ value -= (u64)address;
+ *(u32 *)location = value;
+ break;
+ default:
+ pr_err("Unknown rela relocation: %llu\n",
+ ELF64_R_TYPE(rel[i].r_info));
+ return -ENOEXEC;
+ }
+ }
+ return 0;
+
+overflow:
+ pr_err("Overflow in relocation type %d value 0x%lx\n",
+ (int)ELF64_R_TYPE(rel[i].r_info), value);
+ return -ENOEXEC;
+}