Commit b56b36ee authored by Josh Poimboeuf's avatar Josh Poimboeuf Committed by Jiri Kosina
Browse files

livepatch: Cleanup module page permission changes 



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: default avatarMiroslav Benes <mbenes@suse.cz>
Signed-off-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
Reviewed-by: default avatarPetr Mladek <pmladek@suse.com>
Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
parent fc284d63

arch/x86/kernel/livepatch.c

+2 −23
Original line number Diff line number Diff line
@@ -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);

}

kernel/livepatch/core.c

+11 −5
Original line number Diff line number Diff line
@@ -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,

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