From 162e006ef59266b9ebf34e3d15ca1f3d9ee956d7 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Mon, 5 Feb 2007 21:18:41 +0100 Subject: [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: Heiko Carstens Signed-off-by: Martin Schwidefsky --- arch/s390/kernel/kprobes.c | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) (limited to 'arch/s390/kernel/kprobes.c') diff --git a/arch/s390/kernel/kprobes.c b/arch/s390/kernel/kprobes.c index b2e1dc89a8c..a466bab6677 100644 --- a/arch/s390/kernel/kprobes.c +++ b/arch/s390/kernel/kprobes.c @@ -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" - "1: la %0,0\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; } -- cgit v1.2.3