On 11/09, Oleg Nesterov wrote:
>
> On 11/09, Oleg Nesterov wrote:
> >
> > Note: TASK_SIZE doesn't look right at least on x86, I think it should
> > be replaced by TASK_SIZE_MAX.
> > ...
> > --- x/arch/x86/kernel/hw_breakpoint.c
> > +++ x/arch/x86/kernel/hw_breakpoint.c
> > @@ -200,7 +200,7 @@ int arch_check_bp_in_kernelspace(struct
> > va = info->address;
> > len = get_hbp_len(info->len);
> >
> > - return (va >= TASK_SIZE) && ((va + len - 1) >= TASK_SIZE);
> > + return (va >= TASK_SIZE) || ((va + len - 1) >= TASK_SIZE);
>
> But actully I'd like to ask another question.
>
> Can't we add the additional !in_gate_area_no_mm() check to allow
> the hw breakpoints in vsyscall?
>
> Quoting Amnon:
>
> My service needs to catch the system-calls of its traced son.
> Almost all system-calls are caught with PTRACE_SYSCALL, but not those
> using the vsyscall page - especially "gettimeofday()" and "time()".
>
> ...
>
> However, the code in "arch/x86/kernel/ptrace.c" forbids catching kernel
> addresses.
>
> I tend to agree with Amnon...
>
> What do you think?
ping ;)
I agree the patch I sent is very minor (although it looks like the trivial
bugfix to me).
Just I think Amnon has a point, shouldn't we change this change like below?
(on top of this fixlet).
Oleg.
--- x/arch/x86/kernel/hw_breakpoint.c
+++ x/arch/x86/kernel/hw_breakpoint.c
@@ -188,6 +188,11 @@ static int get_hbp_len(u8 hbp_len)
return len_in_bytes;
}
+static inline bool bp_in_gate(unsigned long start, unsigned long end)
+{
+ return in_gate_area_no_mm(start) && in_gate_area_no_mm(end);
+}
+
/*
* Check for virtual address in kernel space.
*/
@@ -200,7 +205,8 @@ int arch_check_bp_in_kernelspace(struct
va = info->address;
len = get_hbp_len(info->len);
- return (va >= TASK_SIZE) || ((va + len - 1) >= TASK_SIZE);
+ return ((va >= TASK_SIZE) || ((va + len - 1) >= TASK_SIZE)) &&
+ !bp_in_gate(va, va + len - 1);
}
int arch_bp_generic_fields(int x86_len, int x86_type,
--
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