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MIPS Kprobes: Deny probes on ll/sc instructions 

As ll/sc instruction are for atomic read-modify-write operations, allowing
probes on top of these insturctions is a bad idea.

Signed-off-by: Victor Kamensky <kamensky@cisco.com>
Signed-off-by: Maneesh Soni <manesoni@cisco.com>
Cc: David Daney <david.daney@cavium.com>
Cc: ananth@in.ibm.com
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/2912/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
hifive-unleashed-5.1
Maneesh Soni 2011-11-08 17:05:35 +05:30 committed by Ralf Baechle
parent 41dde781f5
commit 9233c1ee71
1 changed files with 31 additions and 0 deletions
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31
arch/mips/kernel/kprobes.c
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@ -113,6 +113,30 @@ insn_ok:
return 0;
}
/*
* insn_has_ll_or_sc function checks whether instruction is ll or sc
* one; putting breakpoint on top of atomic ll/sc pair is bad idea;
* so we need to prevent it and refuse kprobes insertion for such
* instructions; cannot do much about breakpoint in the middle of
* ll/sc pair; it is upto user to avoid those places
*/
static int __kprobes insn_has_ll_or_sc(union mips_instruction insn)
{
int ret = 0;
switch (insn.i_format.opcode) {
case ll_op:
case lld_op:
case sc_op:
case scd_op:
ret = 1;
break;
default:
break;
}
return ret;
}
int __kprobes arch_prepare_kprobe(struct kprobe *p)
{
union mips_instruction insn;
@ -121,6 +145,13 @@ int __kprobes arch_prepare_kprobe(struct kprobe *p)
insn = p->addr[0];
if (insn_has_ll_or_sc(insn)) {
pr_notice("Kprobes for ll and sc instructions are not"
"supported\n");
ret = -EINVAL;
goto out;
}
if (insn_has_delayslot(insn)) {
pr_notice("Kprobes for branch and jump instructions are not"
"supported\n");