linux-kernel - Re: [PATCH] MIPS: Fix ptrace(2) PTRACE_PEEKUSR and PTRACE

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Date:   Mon, 14 May 2018 23:37:16 +0100
From:   James Hogan <jhogan@...nel.org>
To:     "Maciej W. Rozycki" <macro@...s.com>
Cc:     Ralf Baechle <ralf@...ux-mips.org>, linux-mips@...ux-mips.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] MIPS: Fix ptrace(2) PTRACE_PEEKUSR and PTRACE_POKEUSR
 accesses to o32 FGRs

On Mon, May 14, 2018 at 04:49:43PM +0100, Maciej W. Rozycki wrote:
> Check the TIF_32BIT_FPREGS task setting of the tracee rather than the 
> tracer in determining the layout of floating-point general registers in 
> the floating-point context, correcting access to odd-numbered registers 
> for o32 tracees where the setting disagrees between the two processes.
> 
> Cc: stable@...r.kernel.org # 3.14+
> Fixes: 597ce1723e0f ("MIPS: Support for 64-bit FP with O32 binaries")
> Signed-off-by: Maciej W. Rozycki <macro@...s.com>
> ---
> Hi,
> 
>  These are not the usual requests used by GDB to access the floating-point 
> context, which is likely why it went unnoticed so long.  They are only 
> used as a fallback in the case where PTRACE_GETFPREGS and PTRACE_SETFPREGS 
> requests are not supported, i.e. with ancient kernels.
> 
>  However to verify an unrelated GDB bug fix I have tweaked GDB to always 
> use PTRACE_PEEKUSR and PTRACE_POKEUSR, and then discovered this issue in 
> native GDB regression testing, as it showed regressions from corrupt FGR 
> contents across numerous tests compared to the usual results.  This fix 
> removed those regressions then.
> 
>  Not being typically used does not mean we ought to keep the interface 
> broken.  Therefore please apply.

Looks good. Applied to fixes branch for 4.17.

Thanks
James

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