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x86: debugctlmsr kprobes

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This adjusts the x86 kprobes implementation to cope with per-thread
MSR_IA32_DEBUGCTLMSR being set for user mode.  I haven't delved deep
enough into the kprobes code to be really sure this covers all the
cases where the user-mode BTF setting needs to be cleared or restored.
It looks about right to me.

Signed-off-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Roland McGrath 2008-01-30 13:30:54 +01:00 committed by Ingo Molnar
parent 10faa81e10
commit 1ecc798c67
2 changed files with 29 additions and 0 deletions
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15
arch/x86/kernel/kprobes_32.c
View File

@ -217,8 +217,21 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
kcb->kprobe_saved_eflags &= ~IF_MASK; kcb->kprobe_saved_eflags &= ~IF_MASK;
} }
static __always_inline void clear_btf(void)
{
if (test_thread_flag(TIF_DEBUGCTLMSR))
wrmsr(MSR_IA32_DEBUGCTLMSR, 0, 0);
}
static __always_inline void restore_btf(void)
{
if (test_thread_flag(TIF_DEBUGCTLMSR))
wrmsr(MSR_IA32_DEBUGCTLMSR, current->thread.debugctlmsr, 0);
}
static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs) static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{ {
clear_btf();
regs->eflags |= TF_MASK; regs->eflags |= TF_MASK;
regs->eflags &= ~IF_MASK; regs->eflags &= ~IF_MASK;
/*single step inline if the instruction is an int3*/ /*single step inline if the instruction is an int3*/
@ -542,6 +555,8 @@ static void __kprobes resume_execution(struct kprobe *p,
regs->eip = orig_eip + (regs->eip - copy_eip); regs->eip = orig_eip + (regs->eip - copy_eip);
no_change: no_change:
restore_btf();
return; return;
} }

14
arch/x86/kernel/kprobes_64.c
View File

@ -256,8 +256,21 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
kcb->kprobe_saved_rflags &= ~IF_MASK; kcb->kprobe_saved_rflags &= ~IF_MASK;
} }
static __always_inline void clear_btf(void)
{
if (test_thread_flag(TIF_DEBUGCTLMSR))
wrmsrl(MSR_IA32_DEBUGCTLMSR, 0);
}
static __always_inline void restore_btf(void)
{
if (test_thread_flag(TIF_DEBUGCTLMSR))
wrmsrl(MSR_IA32_DEBUGCTLMSR, current->thread.debugctlmsr);
}
static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs) static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
{ {
clear_btf();
regs->eflags |= TF_MASK; regs->eflags |= TF_MASK;
regs->eflags &= ~IF_MASK; regs->eflags &= ~IF_MASK;
/*single step inline if the instruction is an int3*/ /*single step inline if the instruction is an int3*/
@ -527,6 +540,7 @@ static void __kprobes resume_execution(struct kprobe *p,
regs->rip = orig_rip + (regs->rip - copy_rip); regs->rip = orig_rip + (regs->rip - copy_rip);
no_change: no_change:
restore_btf();
return; return;
} }