Calling set_memory_rw() and set_memory_ro() for every iteration of the
loop in klp_write_object_relocations() is messy, inefficient, and
error-prone.
Change all the read-only pages to read-write before the loop and convert
them back to read-only again afterwards.
Suggested-by: Miroslav Benes <mbe...@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoim...@redhat.com>
---
Based on the following branches:
- git://git.kernel.org/pub/scm/linux/kernel/git/jikos/livepatching.git
for-4.5/core
- git://git.kernel.org/pub/scm/linux/kernel/git/rusty/linux.git modules-next
- v4: rebase onto Chris's sympos changes
- v3: use new module_{disable,enable}_ro() functions (in linux-next)
arch/x86/kernel/livepatch.c | 25 ++-----------------------
kernel/livepatch/core.c | 16 +++++++++++-----
2 files changed, 13 insertions(+), 28 deletions(-)
diff --git a/arch/x86/kernel/livepatch.c b/arch/x86/kernel/livepatch.c
index bcc06e8..92fc1a5 100644
--- a/arch/x86/kernel/livepatch.c
+++ b/arch/x86/kernel/livepatch.c
@@ -20,8 +20,6 @@
#include <linux/module.h>
#include <linux/uaccess.h>
-#include <asm/cacheflush.h>
-#include <asm/page_types.h>
#include <asm/elf.h>
#include <asm/livepatch.h>
@@ -38,8 +36,7 @@
int klp_write_module_reloc(struct module *mod, unsigned long type,
unsigned long loc, unsigned long value)
{
- int ret, numpages, size = 4;
- bool readonly;
+ size_t size = 4;
unsigned long val;
unsigned long core = (unsigned long)mod->core_layout.base;
unsigned long core_size = mod->core_layout.size;
@@ -69,23 +66,5 @@ int klp_write_module_reloc(struct module *mod, unsigned long
type,
/* loc does not point to any symbol inside the module */
return -EINVAL;
- readonly = false;
-
-#ifdef CONFIG_DEBUG_SET_MODULE_RONX
- if (loc < core + mod->core_layout.ro_size)
- readonly = true;
-#endif
-
- /* determine if the relocation spans a page boundary */
- numpages = ((loc & PAGE_MASK) == ((loc + size) & PAGE_MASK)) ? 1 : 2;
-
- if (readonly)
- set_memory_rw(loc & PAGE_MASK, numpages);
-
- ret = probe_kernel_write((void *)loc, &val, size);
-
- if (readonly)
- set_memory_ro(loc & PAGE_MASK, numpages);
-
- return ret;
+ return probe_kernel_write((void *)loc, &val, size);
}
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 94893e8..bc2c85c 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -28,6 +28,7 @@
#include <linux/list.h>
#include <linux/kallsyms.h>
#include <linux/livepatch.h>
+#include <asm/cacheflush.h>
/**
* struct klp_ops - structure for tracking registered ftrace ops structs
@@ -232,7 +233,7 @@ static int klp_find_external_symbol(struct module *pmod,
const char *name,
static int klp_write_object_relocations(struct module *pmod,
struct klp_object *obj)
{
- int ret;
+ int ret = 0;
unsigned long val;
struct klp_reloc *reloc;
@@ -242,13 +243,16 @@ static int klp_write_object_relocations(struct module
*pmod,
if (WARN_ON(!obj->relocs))
return -EINVAL;
+ module_disable_ro(pmod);
+
for (reloc = obj->relocs; reloc->name; reloc++) {
/* discover the address of the referenced symbol */
if (reloc->external) {
if (reloc->sympos > 0) {
pr_err("non-zero sympos for external reloc
symbol '%s' is not supported\n",
reloc->name);
- return -EINVAL;
+ ret = -EINVAL;
+ goto out;
}
ret = klp_find_external_symbol(pmod, reloc->name, &val);
} else
@@ -257,18 +261,20 @@ static int klp_write_object_relocations(struct module
*pmod,
reloc->sympos,
&val);
if (ret)
- return ret;
+ goto out;
ret = klp_write_module_reloc(pmod, reloc->type, reloc->loc,
val + reloc->addend);
if (ret) {
pr_err("relocation failed for symbol '%s' at 0x%016lx
(%d)\n",
reloc->name, val, ret);
- return ret;
+ goto out;
}
}
- return 0;
+out:
+ module_enable_ro(pmod);
+ return ret;
}
static void notrace klp_ftrace_handler(unsigned long ip,
--
2.4.3
--
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