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Commit 162e006e authored by Heiko Carstens's avatar Heiko Carstens Committed by Martin Schwidefsky
Browse files

[S390] Mark kernel text section read-only. 



Set read-only flag in the page table entries for the kernel image text
section. This will catch all instruction caused corruptions withing the
text section.
Instruction replacement via kprobes still works, since it bypasses now
dynamic address translation.

Signed-off-by: default avatarHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent ab14de6c

arch/s390/kernel/early.c

+0 −1
Original line number Diff line number Diff line
@@ -27,7 +27,6 @@ 
#define DEFSYS_CMD_SIZE		96

#define SAVESYS_CMD_SIZE	32



extern int _eshared;

char kernel_nss_name[NSS_NAME_SIZE + 1];



#ifdef CONFIG_SHARED_KERNEL

arch/s390/kernel/kprobes.c

+23 −4
Original line number Diff line number Diff line
@@ -155,15 +155,34 @@ void __kprobes get_instruction_type(struct arch_specific_insn *ainsn) 
static int __kprobes swap_instruction(void *aref)

{

	struct ins_replace_args *args = aref;

	u32 *addr;

	u32 instr;

	int err = -EFAULT;



	/*

	 * Text segment is read-only, hence we use stura to bypass dynamic

	 * address translation to exchange the instruction. Since stura

	 * always operates on four bytes, but we only want to exchange two

	 * bytes do some calculations to get things right. In addition we

	 * shall not cross any page boundaries (vmalloc area!) when writing

	 * the new instruction.

	 */

	addr = (u32 *)ALIGN((unsigned long)args->ptr, 4);

	if ((unsigned long)args->ptr & 2)

		instr = ((*addr) & 0xffff0000) | args->new;

	else

		instr = ((*addr) & 0x0000ffff) | args->new << 16;



	asm volatile(

		"0: mvc  0(2,%2),0(%3)\n"

		"	lra	%1,0(%1)\n"

		"0:	stura	%2,%1\n"

		"1:	la	%0,0\n"

		"2:\n"

		EX_TABLE(0b,2b)

		: "+d" (err), "=m" (*args->ptr)

		: "a" (args->ptr), "a" (&args->new), "m" (args->new));

		: "+d" (err)

		: "a" (addr), "d" (instr)

		: "memory", "cc");



	return err;

}

arch/s390/kernel/vmlinux.lds.S

+2 −1
Original line number Diff line number Diff line
@@ -35,9 +35,10 @@ SECTIONS 


#ifdef CONFIG_SHARED_KERNEL

  . = ALIGN(1048576);		/* VM shared segments are 1MB aligned */

#endif



  . = ALIGN(4096);

  _eshared = .;			/* End of shareable data */

#endif



  . = ALIGN(16);		/* Exception table */

  __start___ex_table = .;

arch/s390/mm/init.c

+4 −5
Original line number Diff line number Diff line
@@ -26,7 +26,6 @@ 
#include <linux/pfn.h>

#include <linux/poison.h>

#include <linux/initrd.h>



#include <asm/processor.h>

#include <asm/system.h>

#include <asm/uaccess.h>
@@ -96,8 +95,8 @@ static void __init setup_ro_region(void) 
	pte_t new_pte;

	unsigned long address, end;



	address = ((unsigned long)&__start_rodata) & PAGE_MASK;

	end = PFN_ALIGN((unsigned long)&__end_rodata);

	address = ((unsigned long)&_stext) & PAGE_MASK;

	end = PFN_ALIGN((unsigned long)&_eshared);



	for (; address < end; address += PAGE_SIZE) {

		pgd = pgd_offset_k(address);
@@ -173,8 +172,8 @@ void __init mem_init(void) 
                datasize >>10,

                initsize >> 10);

	printk("Write protected kernel read-only data: %#lx - %#lx\n",

	       (unsigned long)&__start_rodata,

	       PFN_ALIGN((unsigned long)&__end_rodata) - 1);

	       (unsigned long)&_stext,

	       PFN_ALIGN((unsigned long)&_eshared) - 1);

}



void free_initmem(void)

include/asm-s390/sections.h

+2 −0
Original line number Diff line number Diff line
@@ -3,4 +3,6 @@ 


#include <asm-generic/sections.h>



extern char _eshared[];



#endif