linux-kernel - [PATCH 3.16 064/158] MIPS: ptrace: Avoid smp_processor

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Date:	Mon, 15 Sep 2014 12:25:03 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Alex Smith <alex@...x-smith.me.uk>,
	linux-mips@...ux-mips.org, Ralf Baechle <ralf@...ux-mips.org>
Subject: [PATCH 3.16 064/158] MIPS: ptrace: Avoid smp_processor_id() when retrieving FPU IR

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

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

From: Alex Smith <alex@...x-smith.me.uk>

commit 656ff9bef08c19a6471b49528dacb4cbbeb1e537 upstream.

Whenever ptrace attempts to retrieve the FPU implementation register it
accesses it through current_cpu_data, which calls smp_processor_id().
Since the code may execute with preemption enabled, this can trigger
a warning. Fix this by using boot_cpu_data to get the IR instead.

Signed-off-by: Alex Smith <alex@...x-smith.me.uk>
Cc: linux-mips@...ux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/7449/
Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/mips/kernel/ptrace.c   |    4 ++--
 arch/mips/kernel/ptrace32.c |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/arch/mips/kernel/ptrace.c
+++ b/arch/mips/kernel/ptrace.c
@@ -129,7 +129,7 @@ int ptrace_getfpregs(struct task_struct
 	}
 
 	__put_user(child->thread.fpu.fcr31, data + 64);
-	__put_user(current_cpu_data.fpu_id, data + 65);
+	__put_user(boot_cpu_data.fpu_id, data + 65);
 
 	return 0;
 }
@@ -611,7 +611,7 @@ long arch_ptrace(struct task_struct *chi
 			break;
 		case FPC_EIR:
 			/* implementation / version register */
-			tmp = current_cpu_data.fpu_id;
+			tmp = boot_cpu_data.fpu_id;
 			break;
 		case DSP_BASE ... DSP_BASE + 5: {
 			dspreg_t *dregs;
--- a/arch/mips/kernel/ptrace32.c
+++ b/arch/mips/kernel/ptrace32.c
@@ -129,7 +129,7 @@ long compat_arch_ptrace(struct task_stru
 			break;
 		case FPC_EIR:
 			/* implementation / version register */
-			tmp = current_cpu_data.fpu_id;
+			tmp = boot_cpu_data.fpu_id;
 			break;
 		case DSP_BASE ... DSP_BASE + 5: {
 			dspreg_t *dregs;


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