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s390/kprobes: make insn pages read-only

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Make sure that kprobe insn pages are not writable anymore.

Tested-by: Vasily Gorbik <gor@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2020-09-10 16:48:35 +02:00 committed by Vasily Gorbik
parent c3b2c9064e
commit 6c6687a444
1 changed files with 39 additions and 18 deletions
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57
arch/s390/kernel/kprobes.c
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@ -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;
/*
* 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];
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;
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.
*/
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 *)&insn[1] = new_disp;
}
s390_kernel_write(p->ainsn.insn, &insn, len);
}
NOKPROBE_SYMBOL(copy_instruction);