[PATCH] MIPS: ptrace: Fix PTRACE_PEEKUSR requests for 64-bit FGRs

Maciej W. Rozycki
2018-05-16T15:40:41Z

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: <stable@vger.kernel.org> # 3.19+
Fixes: bbd426f542cb ("MIPS: Simplify FP context access")
Signed-off-by: Maciej W. Rozycki <macro@mips.com>
---
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 2018-05-15 17:44:25.000000000 +0100
+++ linux/arch/mips/kernel/ptrace.c 2018-05-16 11:22:00.714605000 +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 2018-05-15 17:45:16.000000000 +0100
+++ linux/arch/mips/kernel/ptrace32.c 2018-05-16 11:22:16.313698000 +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;