[PATCH] arm64: ptrace: fix setting hw breakpoint/watchpoint

[catalin.udma at freescale.com]

Thank you, Will. The gdb patch seems to solve the problem.

As long as the kernel can rely on the registers number sent from GDB,
then there is no need for this kernel patch.

Regards,
Catalin


> -----Original Message-----
> From: Will Deacon [mailto:will.deacon at arm.com]
> Sent: Friday, May 16, 2014 4:44 PM
> To: Udma Catalin-Dan-B32721
> Cc: linux-arm-kernel at lists.infradead.org
> Subject: Re: [PATCH] arm64: ptrace: fix setting hw breakpoint/watchpoint
> 
> On Mon, May 05, 2014 at 12:51:25PM +0100, Catalin Udma wrote:
> > When setting hw breakpoints/watchpoints, GDB reports the error
> > "Unexpected error setting hardware debug registers". The problem is
> > reproducible on A53/A57 models where the supported number of
> > breakpoints/watchpoints (6 or 4 read from ID_AA64DFR0_EL1) it is
> > less than the maximum number of debug registers from user_hwdebug_state
> >
> > This patch fixes the problem by restricting the registers access to the
> > maximum number of supported breakpoints/watchpoints
> 
> Actually, I consider this to be a bug in GDB. It shouldn't be trying to
> access registers that don't exist (we tell it the number of registers
> available as part of the 32-bit info register).
> 
> I also think this has been fixed in GDB upstream:
> 
> 
>   commit f45c82da381e0ce5ce51b7fb24d0d28611d266b8
>   Author: Yufeng Zhang <yufeng.zhang at arm.com>
>   Date:   Wed Dec 18 16:47:33 2013 +0000
> 
>       gdb/
> 
>           * aarch64-linux-nat.c (aarch64_linux_set_debug_regs): Set
>           iov.iov_len with the real length in use.
> 
>       gdb/gdbserver/
> 
>           * linux-aarch64-low.c (aarch64_linux_set_debug_regs): Set
>           iov.iov_len with the real length in use.
> 
> 
> so there's no need to change the kernel for this.
> 
> Will