Re: ptrace denies access to EFLAGS_RF

[Stephane Eranian <eranian@hpl.hp.com>]

Chuck,

I tired today with 2.6.15-git8 and now it works just fine
on my Opteron box.

Thanks for your help.

On Fri, Jan 06, 2006 at 11:10:16AM -0500, Chuck Ebbert wrote:
> In-Reply-To: <20060106140217.GD7676@frankl.hpl.hp.com>
> 
> On Fri, 6 Jan 2006 at 06:02:17 -0800, Stephane Eranian wrote:
> 
> 
> > To my surprise, applying the same fix to the x86_64 does not
> > solve the problem on my Opteron box. I verified that the
> > offset (144) matches with what the kernel is expecting.
> > Somehow the RF is lost or not set in the proper location.
> > I cannot make forward progress once I reach the breakpoint.
> 
> 
> I sent this to Andi this morning.  Does it work for you?
> 
> Signed-off-by: Chuck Ebbert <76306.1226@compuserve.com>
> 
>  arch/x86_64/ia32/ptrace32.c |    9 ++++++---
>  arch/x86_64/kernel/ptrace.c |    9 ++++++---
>  2 files changed, 12 insertions(+), 6 deletions(-)
> 
> --- 2.6.15-64a.orig/arch/x86_64/ia32/ptrace32.c
> +++ 2.6.15-64a/arch/x86_64/ia32/ptrace32.c
> @@ -28,9 +28,12 @@
>  #include <asm/i387.h>
>  #include <asm/fpu32.h>
>  
> -/* determines which flags the user has access to. */
> -/* 1 = access 0 = no access */
> -#define FLAG_MASK 0x44dd5UL
> +/*
> + * Determines which flags the user has access to [1 = access, 0 = no access].
> + * Prohibits changing ID(21), VIP(20), VIF(19), VM(17), IOPL(12-13), IF(9).
> + * Also masks reserved bits (31-22, 15, 5, 3, 1).
> + */
> +#define FLAG_MASK 0x54dd5UL
>  
>  #define R32(l,q) \
>  	case offsetof(struct user32, regs.l): stack[offsetof(struct pt_regs, q)/8] = val; break
> --- 2.6.15-64a.orig/arch/x86_64/kernel/ptrace.c
> +++ 2.6.15-64a/arch/x86_64/kernel/ptrace.c
> @@ -36,9 +36,12 @@
>   * in exit.c or in signal.c.
>   */
>  
> -/* determines which flags the user has access to. */
> -/* 1 = access 0 = no access */
> -#define FLAG_MASK 0x44dd5UL
> +/*
> + * Determines which flags the user has access to [1 = access, 0 = no access].
> + * Prohibits changing ID(21), VIP(20), VIF(19), VM(17), IOPL(12-13), IF(9).
> + * Also masks reserved bits (63-22, 15, 5, 3, 1).
> + */
> +#define FLAG_MASK 0x54dd5UL
>  
>  /* set's the trap flag. */
>  #define TRAP_FLAG 0x100UL
> -- 
> Chuck
> Currently reading: _Thud!_ by Terry Pratchett

-- 

-Stephane