[PATCH 4.4 26/37] MIPS: ptrace: Fix PTRACE_PEEKUSR requests for 64-bit FGRs

[PATCH 4.4 26/37] MIPS: ptrace: Fix PTRACE_PEEKUSR requests for 64-bit FGRs

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maciej W. Rozycki <macro@mips.com>

commit c7e814628df65f424fe197dde73bfc67e4a244d7 upstream.

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.

Fixes: bbd426f542cb ("MIPS: Simplify FP context access")
Signed-off-by: Maciej W. Rozycki <macro@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 3.15+
Patchwork: https://patchwork.linux-mips.org/patch/19334/
Signed-off-by: James Hogan <jhogan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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

--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -841,7 +841,7 @@ 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;
--- a/arch/mips/kernel/ptrace32.c
+++ b/arch/mips/kernel/ptrace32.c
@@ -107,7 +107,7 @@ 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;

[PATCH 4.4 27/37] MIPS: prctl: Disallow FRE without FR with PR_SET_FP_MODE requests

[Greg Kroah-Hartman]

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Maciej W. Rozycki <macro@mips.com>

commit 28e4213dd331e944e7fca1954a946829162ed9d4 upstream.

Having PR_FP_MODE_FRE (i.e. Config5.FRE) set without PR_FP_MODE_FR (i.e.
Status.FR) is not supported as the lone purpose of Config5.FRE is to
emulate Status.FR=0 handling on FPU hardware that has Status.FR=1
hardwired[1][2].  Also we do not handle this case elsewhere, and assume
throughout our code that TIF_HYBRID_FPREGS and TIF_32BIT_FPREGS cannot
be set both at once for a task, leading to inconsistent behaviour if
this does happen.

Return unsuccessfully then from prctl(2) PR_SET_FP_MODE calls requesting
PR_FP_MODE_FRE to be set with PR_FP_MODE_FR clear.  This corresponds to
modes allowed by `mips_set_personality_fp'.

References:

[1] "MIPS Architecture For Programmers, Vol. III: MIPS32 / microMIPS32
    Privileged Resource Architecture", Imagination Technologies,
    Document Number: MD00090, Revision 6.02, July 10, 2015, Table 9.69
    "Config5 Register Field Descriptions", p. 262

[2] "MIPS Architecture For Programmers, Volume III: MIPS64 / microMIPS64
    Privileged Resource Architecture", Imagination Technologies,
    Document Number: MD00091, Revision 6.03, December 22, 2015, Table
    9.72 "Config5 Register Field Descriptions", p. 288

Fixes: 9791554b45a2 ("MIPS,prctl: add PR_[GS]ET_FP_MODE prctl options for MIPS")
Signed-off-by: Maciej W. Rozycki <macro@mips.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: <stable@vger.kernel.org> # 4.0+
Patchwork: https://patchwork.linux-mips.org/patch/19327/
Signed-off-by: James Hogan <jhogan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/mips/kernel/process.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/arch/mips/kernel/process.c
+++ b/arch/mips/kernel/process.c
@@ -680,6 +680,10 @@ int mips_set_process_fp_mode(struct task
 	if (value & ~known_bits)
 		return -EOPNOTSUPP;
 
+	/* Setting FRE without FR is not supported.  */
+	if ((value & (PR_FP_MODE_FR | PR_FP_MODE_FRE)) == PR_FP_MODE_FRE)
+		return -EOPNOTSUPP;
+
 	/* Avoid inadvertently triggering emulation */
 	if ((value & PR_FP_MODE_FR) && raw_cpu_has_fpu &&
 	    !(raw_current_cpu_data.fpu_id & MIPS_FPIR_F64))