x32: Add a thread flag for x32 processes

An x32 process is *almost* the same thing as a 64-bit process with a
32-bit address limit, but there are a few minor differences -- in
particular core dumps are 32 bits and signal handling is different.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

2 files changed, 4 insertions, 0 deletions

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index d1803a495b35..912e93511466 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -96,6 +96,7 @@ struct thread_info {
 #define TIF_LAZY_MMU_UPDATES    27      /* task is updating the mmu lazily */
 #define TIF_SYSCALL_TRACEPOINT  28      /* syscall tracepoint instrumentation */
 #define TIF_ADDR32              29      /* 32-bit address space on 64 bits */
+#define TIF_X32                 30      /* 32-bit native x86-64 binary */
 
 #define _TIF_SYSCALL_TRACE      (1 << TIF_SYSCALL_TRACE)
 #define _TIF_NOTIFY_RESUME      (1 << TIF_NOTIFY_RESUME)
@@ -118,6 +119,7 @@ struct thread_info {
 #define _TIF_LAZY_MMU_UPDATES   (1 << TIF_LAZY_MMU_UPDATES)
 #define _TIF_SYSCALL_TRACEPOINT (1 << TIF_SYSCALL_TRACEPOINT)
 #define _TIF_ADDR32             (1 << TIF_ADDR32)
+#define _TIF_X32                (1 << TIF_X32)
 
 /* work to do in syscall_trace_enter() */
 #define _TIF_WORK_SYSCALL_ENTRY \
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 0e900d09e232..5fe2fbaa56ba 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -509,6 +509,7 @@ void set_personality_64bit(void)
         /* Make sure to be in 64bit mode */
         clear_thread_flag(TIF_IA32);
         clear_thread_flag(TIF_ADDR32);
+        clear_thread_flag(TIF_X32);
 
         /* Ensure the corresponding mm is not marked. */
         if (current->mm)
@@ -528,6 +529,7 @@ void set_personality_ia32(void)
         /* Make sure to be in 32bit mode */
         set_thread_flag(TIF_IA32);
         set_thread_flag(TIF_ADDR32);
+        clear_thread_flag(TIF_X32);
         current->personality |= force_personality32;
 
         /* Mark the associated mm as containing 32-bit tasks. */