[3.19.y-ckt stable] Patch "x86: Make is_64bit_mm() widely available" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    x86: Make is_64bit_mm() widely available

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 7d7577609859a7e83af4159129d8a6262a6a44c1 Mon Sep 17 00:00:00 2001
From: Dave Hansen <dave.hansen at linux.intel.com>
Date: Sun, 7 Jun 2015 11:37:04 -0700
Subject: x86: Make is_64bit_mm() widely available

commit b0e9b09b3bd64e67bba862e238d3757b2482b6de upstream.

The uprobes code has a nice helper, is_64bit_mm(), that consults
both the runtime and compile-time flags for 32-bit support.
Instead of reinventing the wheel, pull it in to an x86 header so
we can use it for MPX.

I prefer passing the 'mm' around to test_thread_flag(TIF_IA32)
because it makes it explicit where the context is coming from.

Signed-off-by: Dave Hansen <dave.hansen at linux.intel.com>
Reviewed-by: Thomas Gleixner <tglx at linutronix.de>
Cc: Andrew Morton <akpm at linux-foundation.org>
Cc: Dave Hansen <dave at sr71.net>
Cc: H. Peter Anvin <hpa at zytor.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Oleg Nesterov <oleg at redhat.com>
Cc: Peter Zijlstra <peterz at infradead.org>
Link: http://lkml.kernel.org/r/20150607183704.F0209999@viggo.jf.intel.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
[ kamal: 3.19-stable prereq for "46561c3 x86/mpx: Do proper get_user() when
  running 32-bit binaries on 64-bit kernels" ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/x86/include/asm/mmu_context.h | 13 +++++++++++++
 arch/x86/kernel/uprobes.c          | 10 +---------
 2 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/mmu_context.h b/arch/x86/include/asm/mmu_context.h
index 1ab38a4..acdeb2be 100644
--- a/arch/x86/include/asm/mmu_context.h
+++ b/arch/x86/include/asm/mmu_context.h
@@ -165,6 +165,19 @@ static inline void arch_exit_mmap(struct mm_struct *mm)
 	paravirt_arch_exit_mmap(mm);
 }

+#ifdef CONFIG_X86_64
+static inline bool is_64bit_mm(struct mm_struct *mm)
+{
+	return	!config_enabled(CONFIG_IA32_EMULATION) ||
+		!(mm->context.ia32_compat == TIF_IA32);
+}
+#else
+static inline bool is_64bit_mm(struct mm_struct *mm)
+{
+	return false;
+}
+#endif
+
 static inline void arch_bprm_mm_init(struct mm_struct *mm,
 		struct vm_area_struct *vma)
 {
diff --git a/arch/x86/kernel/uprobes.c b/arch/x86/kernel/uprobes.c
index 8b96a94..6b1ca70 100644
--- a/arch/x86/kernel/uprobes.c
+++ b/arch/x86/kernel/uprobes.c
@@ -29,6 +29,7 @@
 #include <linux/kdebug.h>
 #include <asm/processor.h>
 #include <asm/insn.h>
+#include <asm/mmu_context.h>

 /* Post-execution fixups. */

@@ -245,11 +246,6 @@ static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool
 }

 #ifdef CONFIG_X86_64
-static inline bool is_64bit_mm(struct mm_struct *mm)
-{
-	return	!config_enabled(CONFIG_IA32_EMULATION) ||
-		!(mm->context.ia32_compat == TIF_IA32);
-}
 /*
  * If arch_uprobe->insn doesn't use rip-relative addressing, return
  * immediately.  Otherwise, rewrite the instruction so that it accesses
@@ -430,10 +426,6 @@ static void riprel_post_xol(struct arch_uprobe *auprobe, struct pt_regs *regs)
 	}
 }
 #else /* 32-bit: */
-static inline bool is_64bit_mm(struct mm_struct *mm)
-{
-	return false;
-}
 /*
  * No RIP-relative addressing on 32-bit
  */
--
1.9.1