MIPS: ptrace: Fix PTRACE_PEEKUSR requests for 64-bit FGRs

19334 diff mbox series

Use 64-bit accesses for 64-bit floating-point general registers with 
PTRACE_PEEKUSR, removing the truncation of their upper halves in the 
FR=1 mode, caused by commit bbd426f542cb ("MIPS: Simplify FP context 
access"), which inadvertently switched them to using 32-bit accesses.

The PTRACE_POKEUSR side is fine as it's never been broken and continues 
using 64-bit accesses.

Cc: <> # 3.19+
Fixes: bbd426f542cb ("MIPS: Simplify FP context access")
Signed-off-by: Maciej W. Rozycki <>
---
Hi,

 Here's another one, spotted in the course of GDB PR gdb/22286 regression 
testing with the n64 ABI.  Please apply.

  Maciej
---
 arch/mips/kernel/ptrace.c   |    2 +-
 arch/mips/kernel/ptrace32.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

linux-mips-ptrace-peekusr-fp64.diff

On Wed, May 16, 2018 at 04:39:58PM +0100, Maciej W. Rozycki wrote:
> Use 64-bit accesses for 64-bit floating-point general registers with 
> PTRACE_PEEKUSR, removing the truncation of their upper halves in the 
> FR=1 mode, caused by commit bbd426f542cb ("MIPS: Simplify FP context 
> access"), which inadvertently switched them to using 32-bit accesses.
> 
> The PTRACE_POKEUSR side is fine as it's never been broken and continues 
> using 64-bit accesses.
> 
> Cc: <> # 3.19+

should that be 3.15+?

Cheers
James

On Thu, 24 May 2018, James Hogan wrote:

> > Use 64-bit accesses for 64-bit floating-point general registers with 
> > PTRACE_PEEKUSR, removing the truncation of their upper halves in the 
> > FR=1 mode, caused by commit bbd426f542cb ("MIPS: Simplify FP context 
> > access"), which inadvertently switched them to using 32-bit accesses.
> > 
> > The PTRACE_POKEUSR side is fine as it's never been broken and continues 
> > using 64-bit accesses.
> > 
> > Cc: <> # 3.19+
> 
> should that be 3.15+?

 Indeed, I must have used the wrong result; thank you for catching this!

  Maciej

Hi Maciej,

On Wed, May 16, 2018 at 04:39:58PM +0100, Maciej W. Rozycki wrote:
> Use 64-bit accesses for 64-bit floating-point general registers with 
> PTRACE_PEEKUSR, removing the truncation of their upper halves in the 
> FR=1 mode, caused by commit bbd426f542cb ("MIPS: Simplify FP context 
> access"), which inadvertently switched them to using 32-bit accesses.

Good catch:

  Reviewed-by: Paul Burton <>

Thanks,
  Paul

> The PTRACE_POKEUSR side is fine as it's never been broken and continues 
> using 64-bit accesses.
> 
> Cc: <> # 3.19+
> Fixes: bbd426f542cb ("MIPS: Simplify FP context access")
> Signed-off-by: Maciej W. Rozycki <>
> ---
> Hi,
> 
>  Here's another one, spotted in the course of GDB PR gdb/22286 regression 
> testing with the n64 ABI.  Please apply.
> 
>   Maciej
> ---
>  arch/mips/kernel/ptrace.c   |    2 +-
>  arch/mips/kernel/ptrace32.c |    2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> linux-mips-ptrace-peekusr-fp64.diff
> Index: linux/arch/mips/kernel/ptrace.c
> ===================================================================
> --- linux.orig/arch/mips/kernel/ptrace.c	:44:25. +0100
> +++ linux/arch/mips/kernel/ptrace.c	:22: +0100
> @@ -1070,7 +1070,7 @@ long arch_ptrace(struct task_struct *chi
>  				break;
>  			}
>  #endif
> -			tmp = get_fpr32(&fregs[addr - FPR_BASE], 0);
> +			tmp = get_fpr64(&fregs[addr - FPR_BASE], 0);
>  			break;
>  		case PC:
>  			tmp = regs->cp0_epc;
> Index: linux/arch/mips/kernel/ptrace32.c
> ===================================================================
> --- linux.orig/arch/mips/kernel/ptrace32.c	:45:16. +0100
> +++ linux/arch/mips/kernel/ptrace32.c	:22: +0100
> @@ -109,7 +109,7 @@ long compat_arch_ptrace(struct task_stru
>  						addr & 1);
>  				break;
>  			}
> -			tmp = get_fpr32(&fregs[addr - FPR_BASE], 0);
> +			tmp = get_fpr64(&fregs[addr - FPR_BASE], 0);
>  			break;
>  		case PC:
>  			tmp = regs->cp0_epc;
>

On Wed, May 16, 2018 at 04:39:58PM +0100, Maciej W. Rozycki wrote:
> Use 64-bit accesses for 64-bit floating-point general registers with 
> PTRACE_PEEKUSR, removing the truncation of their upper halves in the 
> FR=1 mode, caused by commit bbd426f542cb ("MIPS: Simplify FP context 
> access"), which inadvertently switched them to using 32-bit accesses.
> 
> The PTRACE_POKEUSR side is fine as it's never been broken and continues 
> using 64-bit accesses.
> 
> Cc: <> # 3.19+
> Fixes: bbd426f542cb ("MIPS: Simplify FP context access")
> Signed-off-by: Maciej W. Rozycki <>
> ---
> Hi,
> 
>  Here's another one, spotted in the course of GDB PR gdb/22286 regression 
> testing with the n64 ABI.  Please apply.
> 
>   Maciej

Thanks, applied to mips-fixes, hopefully for 4.17 (but if it misses
tomorrows linux-next it may have to wait 'til 4.18).

Cheers
James