[PATCH 2/5] x86: mark associated mm when running a task in 32 bit compatibility mode

[Stephen Wilson]

This patch simply follows the same practice as for setting the TIF_IA32 flag.
In particular, an mm is marked as holding 32-bit tasks when a 32-bit binary is
exec'ed.  Both ELF and a.out formats are updated.

Signed-off-by: Stephen Wilson <wilsons@xxxxxxxx>
---
 arch/x86/ia32/ia32_aout.c    |    1 +
 arch/x86/kernel/process_64.c |    8 ++++++++
 2 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/arch/x86/ia32/ia32_aout.c b/arch/x86/ia32/ia32_aout.c
index 2d93bdb..95cde43 100644
--- a/arch/x86/ia32/ia32_aout.c
+++ b/arch/x86/ia32/ia32_aout.c
@@ -298,6 +298,7 @@ static int load_aout_binary(struct linux_binprm *bprm, struct pt_regs *regs)
 	/* OK, This is the point of no return */
 	set_personality(PER_LINUX);
 	set_thread_flag(TIF_IA32);
+	current->mm->context.compat = 1;
 
 	setup_new_exec(bprm);
 
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index bd387e8..35f1221 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -501,6 +501,10 @@ void set_personality_64bit(void)
 	/* Make sure to be in 64bit mode */
 	clear_thread_flag(TIF_IA32);
 
+	/* Ensure the corresponding mm is not marked. */
+	if (current->mm)
+		current->mm->context.compat = 0;
+
 	/* TBD: overwrites user setup. Should have two bits.
 	   But 64bit processes have always behaved this way,
 	   so it's not too bad. The main problem is just that
@@ -516,6 +520,10 @@ void set_personality_ia32(void)
 	set_thread_flag(TIF_IA32);
 	current->personality |= force_personality32;
 
+	/* Mark the associated mm as containing 32-bit tasks. */
+	if (current->mm)
+		current->mm->context.compat = 1;
+
 	/* Prepare the first "return" to user space */
 	current_thread_info()->status |= TS_COMPAT;
 }
-- 
1.7.3.5

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