Commit 6c6687a4 authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
Browse files

s390/kprobes: make insn pages read-only 



Make sure that kprobe insn pages are not writable anymore.

Tested-by: default avatarVasily Gorbik <gor@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent c3b2c906

arch/s390/kernel/kprobes.c

+39 −18
Original line number Diff line number Diff line
@@ -7,6 +7,7 @@ 
 * s390 port, used ppc64 as template. Mike Grundy <grundym@us.ibm.com>

 */



#include <linux/moduleloader.h>

#include <linux/kprobes.h>

#include <linux/ptrace.h>

#include <linux/preempt.h>
@@ -32,17 +33,33 @@ DEFINE_INSN_CACHE_OPS(s390_insn); 
static int insn_page_in_use;

static char insn_page[PAGE_SIZE] __aligned(PAGE_SIZE);



void *alloc_insn_page(void)

{

	void *page;



	page = module_alloc(PAGE_SIZE);

	if (!page)

		return NULL;

	__set_memory((unsigned long) page, 1, SET_MEMORY_RO | SET_MEMORY_X);

	return page;

}



void free_insn_page(void *page)

{

	module_memfree(page);

}



static void *alloc_s390_insn_page(void)

{

	if (xchg(&insn_page_in_use, 1) == 1)

		return NULL;

	set_memory_x((unsigned long) &insn_page, 1);

	__set_memory((unsigned long) &insn_page, 1, SET_MEMORY_RO | SET_MEMORY_X);

	return &insn_page;

}



static void free_s390_insn_page(void *page)

{

	set_memory_nx((unsigned long) page, 1);

	__set_memory((unsigned long) page, 1, SET_MEMORY_RW | SET_MEMORY_NX);

	xchg(&insn_page_in_use, 0);

}
@@ -56,25 +73,29 @@ struct kprobe_insn_cache kprobe_s390_insn_slots = { 


static void copy_instruction(struct kprobe *p)

{

	kprobe_opcode_t insn[MAX_INSN_SIZE];

	s64 disp, new_disp;

	u64 addr, new_addr;

	unsigned int len;



	memcpy(p->ainsn.insn, p->addr, insn_length(*p->addr >> 8));

	p->opcode = p->ainsn.insn[0];

	if (!probe_is_insn_relative_long(p->ainsn.insn))

		return;

	len = insn_length(*p->addr >> 8);

	memcpy(&insn, p->addr, len);

	p->opcode = insn[0];

	if (probe_is_insn_relative_long(&insn[0])) {

		/*

	 * For pc-relative instructions in RIL-b or RIL-c format patch the

	 * RI2 displacement field. We have already made sure that the insn

	 * slot for the patched instruction is within the same 2GB area

	 * as the original instruction (either kernel image or module area).

	 * Therefore the new displacement will always fit.

		 * For pc-relative instructions in RIL-b or RIL-c format patch

		 * the RI2 displacement field. We have already made sure that

		 * the insn slot for the patched instruction is within the same

		 * 2GB area as the original instruction (either kernel image or

		 * module area). Therefore the new displacement will always fit.

		 */

	disp = *(s32 *)&p->ainsn.insn[1];

		disp = *(s32 *)&insn[1];

		addr = (u64)(unsigned long)p->addr;

		new_addr = (u64)(unsigned long)p->ainsn.insn;

		new_disp = ((addr + (disp * 2)) - new_addr) / 2;

	*(s32 *)&p->ainsn.insn[1] = new_disp;

		*(s32 *)&insn[1] = new_disp;

	}

	s390_kernel_write(p->ainsn.insn, &insn, len);

}

NOKPROBE_SYMBOL(copy_instruction);