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Subject[RFC PATCH 3/5] x86: interface for accessing indirect branch locations
Date
Adding a C interface to access the locations of indirect branches. To be
used for dynamic patching.

Signed-off-by: Nadav Amit <namit@vmware.com>
---
arch/x86/include/asm/nospec-branch.h | 1 -
arch/x86/include/asm/sections.h | 2 ++
include/linux/module.h | 5 +++++
kernel/module.c | 8 ++++++++
4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h
index bd2d3a41e88c..a4496c141143 100644
--- a/arch/x86/include/asm/nospec-branch.h
+++ b/arch/x86/include/asm/nospec-branch.h
@@ -406,7 +406,6 @@ struct relpoline_entry {
u8 reg;
} __packed;

-
/* The Intel SPEC CTRL MSR base value cache */
extern u64 x86_spec_ctrl_base;

diff --git a/arch/x86/include/asm/sections.h b/arch/x86/include/asm/sections.h
index 8ea1cfdbeabc..e8dd9c40ecd5 100644
--- a/arch/x86/include/asm/sections.h
+++ b/arch/x86/include/asm/sections.h
@@ -4,6 +4,7 @@

#include <asm-generic/sections.h>
#include <asm/extable.h>
+#include <asm/nospec-branch.h>

extern char __brk_base[], __brk_limit[];
extern struct exception_table_entry __stop___ex_table[];
@@ -11,6 +12,7 @@ extern char __end_rodata_aligned[];

#if defined(CONFIG_X86_64)
extern char __end_rodata_hpage_align[];
+extern const struct relpoline_entry __relpolines[], __relpolines_end[];
#endif

#endif /* _ASM_X86_SECTIONS_H */
diff --git a/include/linux/module.h b/include/linux/module.h
index f807f15bebbe..29ff390f8339 100644
--- a/include/linux/module.h
+++ b/include/linux/module.h
@@ -39,6 +39,7 @@ struct modversion_info {

struct module;
struct exception_table_entry;
+struct relpoline_entry;

struct module_kobject {
struct kobject kobj;
@@ -387,6 +388,10 @@ struct module {
unsigned int num_exentries;
struct exception_table_entry *extable;

+ /* Cachepolines */
+ unsigned int num_relpolines;
+ struct relpoline_entry *relpolines;
+
/* Startup function. */
int (*init)(void);

diff --git a/kernel/module.c b/kernel/module.c
index 49a405891587..e34fc28875bd 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -64,6 +64,7 @@
#include <linux/bsearch.h>
#include <linux/dynamic_debug.h>
#include <linux/audit.h>
+#include <asm/nospec-branch.h>
#include <uapi/linux/module.h>
#include "module-internal.h"

@@ -256,6 +257,7 @@ static void mod_update_bounds(struct module *mod)
#ifdef CONFIG_KGDB_KDB
struct list_head *kdb_modules = &modules; /* kdb needs the list of modules */
#endif /* CONFIG_KGDB_KDB */
+struct list_head *cachepoline_modules = &modules;

static void module_assert_mutex(void)
{
@@ -3125,6 +3127,12 @@ static int find_module_sections(struct module *mod, struct load_info *info)
mod->extable = section_objs(info, "__ex_table",
sizeof(*mod->extable), &mod->num_exentries);

+#ifdef CONFIG_X86_64
+ mod->relpolines = section_objs(info, "__relpolines",
+ sizeof(*mod->relpolines),
+ &mod->num_relpolines);
+#endif
+
if (section_addr(info, "__obsparm"))
pr_warn("%s: Ignoring obsolete parameters\n", mod->name);

--
2.17.1
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