Messages in this thread | | | Date | Fri, 9 Mar 2012 11:58:53 +0530 | From | Srikar Dronamraju <> | Subject | Re: [PATCH] uprobes/core: handle breakpoint and signal step exception. |
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* Ingo Molnar <mingo@elte.hu> [2012-03-08 14:48:09]:
> > * Srikar Dronamraju <srikar@linux.vnet.ibm.com> wrote: > > > @@ -233,9 +233,11 @@ static inline void __user *arch_compat_alloc_user_space(long len) > > > > if (test_thread_flag(TIF_IA32)) { > > sp = task_pt_regs(current)->sp; > > +#ifdef CONFIG_X86_64 > > } else { > > /* -128 for the x32 ABI redzone */ > > sp = __this_cpu_read(old_rsp) - 128; > > +#endif > > } > > > > return (void __user *)round_down(sp - len, 16); > > So 'sp' is undefined if that TIF check fails? > > Also, on a 32-bit kernel the TIF check probably fails all the > time, because we don't set TIF_IA32 (and don't know that flag).
> > It would probably be better to make the whole helper inline > #ifdef 64-bit, it does not look very useful on 32-bit. >
arch_compat_alloc_user_space gets called from compat_alloc_user_space which is arch agnostic and exported too.
So I will change this to
void __user *arch_compat_alloc_user_space(long len) { if (is_ia32_compat_task(current)) sp = task_pt_regs(current)->sp; #ifdef CONFIG_X86_64 else /* -128 for the x32 ABI redzone */ sp = __this_cpu_read(old_rsp) - 128; #endif return (void __user *)round_down(sp - len, 16); }
where is_ia32_compat_task() is the new macro that you suggested we put in compat.h which would return true if the task is 32 bit emulated on x86_64 or running on i386 machine.
Hence we can avoid the case where sp is not set.
-- Thanks and Regards Srikar
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