Reuse module loader code to write relocations, thereby eliminating the need
for architecture specific relocation code in livepatch. Namely, we reuse
apply_relocate_add() in the module loader to write relocations instead of
duplicating functionality in livepatch's klp_write_module_reloc(). To apply
relocation sections, remaining SHN_LIVEPATCH symbols referenced by relocs
are resolved and then apply_relocate_add() is called to apply those
relocations.
In addition, remove x86 livepatch relocation code. It is no longer needed
since symbol resolution and relocation work have been offloaded to module
loader.
Signed-off-by: Jessica Yu <redacted>
---
arch/x86/include/asm/livepatch.h | 2 -
arch/x86/kernel/Makefile | 1 -
arch/x86/kernel/livepatch.c | 70 ---------------------------
include/linux/livepatch.h | 33 +++++--------
kernel/livepatch/core.c | 101 +++++++++++++++++++--------------------
5 files changed, 62 insertions(+), 145 deletions(-)
delete mode 100644 arch/x86/kernel/livepatch.c
diff --git a/arch/x86/include/asm/livepatch.h b/arch/x86/include/asm/livepatch.h
index 19c099a..7312e25 100644
--- a/arch/x86/include/asm/livepatch.h
+++ b/arch/x86/include/asm/livepatch.h
@@ -33,8 +33,6 @@ static inline int klp_check_compiler_support(void)
#endif
return 0;
}
-int klp_write_module_reloc(struct module *mod, unsigned long type,
- unsigned long loc, unsigned long value);
static inline void klp_arch_set_pc(struct pt_regs *regs, unsigned long ip)
{diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index b1b78ff..c5e9a5c 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile
@@ -67,7 +67,6 @@ obj-$(CONFIG_X86_MPPARSE) += mpparse.o
obj-y += apic/
obj-$(CONFIG_X86_REBOOTFIXUPS) += reboot_fixups_32.o
obj-$(CONFIG_DYNAMIC_FTRACE) += ftrace.o
-obj-$(CONFIG_LIVEPATCH) += livepatch.o
obj-$(CONFIG_FUNCTION_GRAPH_TRACER) += ftrace.o
obj-$(CONFIG_FTRACE_SYSCALLS) += ftrace.o
obj-$(CONFIG_X86_TSC) += trace_clock.o
diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c
deleted file mode 100644
index 92fc1a5..0000000
--- a/arch/x86/kernel/livepatch.c
+++ /dev/null
@@ -1,70 +0,0 @@
-/*
- * livepatch.c - x86-specific Kernel Live Patching Core
- *
- * Copyright (C) 2014 Seth Jennings <sjenning-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
- * Copyright (C) 2014 SUSE
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, see <http://www.gnu.org/licenses/>.
- */
-
-#include <linux/module.h>
-#include <linux/uaccess.h>
-#include <asm/elf.h>
-#include <asm/livepatch.h>
-
-/**
- * klp_write_module_reloc() - write a relocation in a module
- * @mod: module in which the section to be modified is found
- * @type: ELF relocation type (see asm/elf.h)
- * @loc: address that the relocation should be written to
- * @value: relocation value (sym address + addend)
- *
- * This function writes a relocation to the specified location for
- * a particular module.
- */
-int klp_write_module_reloc(struct module *mod, unsigned long type,
- unsigned long loc, unsigned long value)
-{
- size_t size = 4;
- unsigned long val;
- unsigned long core = (unsigned long)mod->core_layout.base;
- unsigned long core_size = mod->core_layout.size;
-
- switch (type) {
- case R_X86_64_NONE:
- return 0;
- case R_X86_64_64:
- val = value;
- size = 8;
- break;
- case R_X86_64_32:
- val = (u32)value;
- break;
- case R_X86_64_32S:
- val = (s32)value;
- break;
- case R_X86_64_PC32:
- val = (u32)(value - loc);
- break;
- default:
- /* unsupported relocation type */
- return -EINVAL;
- }
-
- if (loc < core || loc >= core + core_size)
- /* loc does not point to any symbol inside the module */
- return -EINVAL;
-
- return probe_kernel_write((void *)loc, &val, size);
-}diff --git a/include/linux/livepatch.h b/include/linux/livepatch.h
index a882865..2f12ce7 100644
--- a/include/linux/livepatch.h
+++ b/include/linux/livepatch.h
@@ -65,27 +65,8 @@ struct klp_func {};
/**
- * struct klp_reloc - relocation structure for live patching
- * @loc: address where the relocation will be written
- * @sympos: position in kallsyms to disambiguate symbols (optional)
- * @type: ELF relocation type
- * @name: name of the referenced symbol (for lookup/verification)
- * @addend: offset from the referenced symbol
- * @external: symbol is either exported or within the live patch module itself
- */
-struct klp_reloc {
- unsigned long loc;
- unsigned long sympos;
- unsigned long type;
- const char *name;
- int addend;
- int external;
-};
-
-/**
* struct klp_object - kernel object structure for live patching
* @name: module name (or NULL for vmlinux)
- * @relocs: relocation entries to be applied at load time
* @funcs: function entries for functions to be patched in the object
* @kobj: kobject for sysfs resources
* @mod: kernel module associated with the patched object@@ -95,7 +76,6 @@ struct klp_reloc {struct klp_object {
/* external */
const char *name;
- struct klp_reloc *relocs;
struct klp_func *funcs;
/* internal */@@ -123,6 +103,19 @@ struct klp_patch { enum klp_state state;
};
+/*
+ * Livepatch-specific symbols and relocation
+ * sections are prefixed with a tag:
+ * .klp.rel. for relocation sections
+ * .klp.sym. for livepatch symbols
+ */
+#define KLP_TAG_LEN 9
+/*
+ * Livepatch-specific bits for specifying symbol
+ * positions in the Elf_Sym st_other field
+ */
+#define KLP_SYMPOS(o) (o >> 2) & 0xff
+