Elf: add livepatch-specific Elf constants

Livepatch manages its own relocation sections and symbols in order to be
able to reuse module loader code to write relocations. This removes
livepatch's dependence on separate "dynrela" sections to write relocations
and also allows livepatch to patch modules that are not yet loaded.

The livepatch Elf relocation section flag (SHF_RELA_LIVEPATCH),
and symbol section index (SHN_LIVEPATCH) allow both livepatch and the
module loader to identity livepatch relocation sections and livepatch
symbols.

Livepatch relocation sections are marked with SHF_RELA_LIVEPATCH to
indicate to the module loader that it should not apply that relocation
section and that livepatch will handle them.

The SHN_LIVEPATCH shndx marks symbols that will be resolved by livepatch.
The module loader ignores these symbols and does not attempt to resolve
them.

The values of these Elf constants were selected from OS-specific
ranges according to the definitions from glibc.

Signed-off-by: Jessica Yu <jeyu@redhat.com>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Acked-by: Josh Poimboeuf <jpoimboe@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 71e1d0e..cb4a72f 100644 (file)
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -282,16 +282,18 @@ typedef struct elf64_phdr {
 #define SHT_HIUSER     0xffffffff
 
 /* sh_flags */
-#define SHF_WRITE      0x1
-#define SHF_ALLOC      0x2
-#define SHF_EXECINSTR  0x4
-#define SHF_MASKPROC   0xf0000000
+#define SHF_WRITE              0x1
+#define SHF_ALLOC              0x2
+#define SHF_EXECINSTR          0x4
+#define SHF_RELA_LIVEPATCH     0x00100000
+#define SHF_MASKPROC           0xf0000000
 
 /* special section indexes */
 #define SHN_UNDEF      0
 #define SHN_LORESERVE  0xff00
 #define SHN_LOPROC     0xff00
 #define SHN_HIPROC     0xff1f
+#define SHN_LIVEPATCH  0xff20
 #define SHN_ABS                0xfff1
 #define SHN_COMMON     0xfff2
 #define SHN_HIRESERVE  0xffff