x86-64: make compat_start_thread() match start_thread()

For no real good reason, compat_start_thread() was embedded inline in
<asm/elf.h> whereas the native start_thread() lives in process_*.c.
Move compat_start_thread() to process_64.c, remove gratuitious
differences, and fix a few items which mostly look like bit rot.

In particular, compat_start_thread() didn't do free_thread_xstate(),
which means it was hanging on to the xstate store area even when it
was not needed.  It was also not setting old_rsp, but it looks like
that generally shouldn't matter for a 32-bit process.

Note: compat_start_thread *has* to be a macro, since it is tested with
start_thread_ia32() as the out of line function name.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Acked-by: Suresh Siddha <suresh.b.siddha@intel.com>

2 files changed, 24 insertions, 19 deletions

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index 456a304b817..8a024babe5e 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -157,19 +157,6 @@ do {						\
 
 #define compat_elf_check_arch(x)        elf_check_arch_ia32(x)
 
-static inline void start_ia32_thread(struct pt_regs *regs, u32 ip, u32 sp)
-{
-        loadsegment(fs, 0);
-        loadsegment(ds, __USER32_DS);
-        loadsegment(es, __USER32_DS);
-        load_gs_index(0);
-        regs->ip = ip;
-        regs->sp = sp;
-        regs->flags = X86_EFLAGS_IF;
-        regs->cs = __USER32_CS;
-        regs->ss = __USER32_DS;
-}
-
 static inline void elf_common_init(struct thread_struct *t,
                                    struct pt_regs *regs, const u16 ds)
 {
@@ -191,11 +178,8 @@ do {							\
 #define COMPAT_ELF_PLAT_INIT(regs, load_addr)           \
         elf_common_init(&current->thread, regs, __USER_DS)
 
-#define compat_start_thread(regs, ip, sp)               \
-do {                                                    \
-        start_ia32_thread(regs, ip, sp);                \
-        set_fs(USER_DS);                                \
-} while (0)
+void start_thread_ia32(struct pt_regs *regs, u32 new_ip, u32 new_sp);
+#define compat_start_thread start_thread_ia32
 
 #define COMPAT_SET_PERSONALITY(ex)                      \
 do {                                                    \
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index ad535b68317..7cf0a6b6d4b 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -356,7 +356,7 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
         percpu_write(old_rsp, new_sp);
         regs->cs                = __USER_CS;
         regs->ss                = __USER_DS;
-        regs->flags             = 0x200;
+        regs->flags             = X86_EFLAGS_IF;
         set_fs(USER_DS);
         /*
          * Free the old FP and other extended state
@@ -365,6 +365,27 @@ start_thread(struct pt_regs *regs, unsigned long new_ip, unsigned long new_sp)
 }
 EXPORT_SYMBOL_GPL(start_thread);
 
+#ifdef CONFIG_IA32_EMULATION
+void start_thread_ia32(struct pt_regs *regs, u32 new_ip, u32 new_sp)
+{
+        loadsegment(fs, 0);
+        loadsegment(ds, __USER32_DS);
+        loadsegment(es, __USER32_DS);
+        load_gs_index(0);
+        regs->ip                = new_ip;
+        regs->sp                = new_sp;
+        percpu_write(old_rsp, new_sp);
+        regs->cs                = __USER32_CS;
+        regs->ss                = __USER32_DS;
+        regs->flags             = X86_EFLAGS_IF;
+        set_fs(USER_DS);
+        /*
+         * Free the old FP and other extended state
+         */
+        free_thread_xstate(current);
+}
+#endif
+
 /*
  *      switch_to(x,y) should switch tasks from x to y.
  *