[PATCHv2 1/5] x86/mm: split arch_mmap_rnd() on compat/native versions

[Dmitry Safonov]

I need those arch_{native,compat}_rnd() to compute separately
random factor for mmap() in compat syscalls for 64-bit binaries
and vice-versa for native syscall in 32-bit compat binaries.
They will be used in the following patches.

Signed-off-by: Dmitry Safonov <dsafonov@xxxxxxxxxxxxx>
---
 arch/x86/include/asm/elf.h |  5 +++++
 arch/x86/mm/mmap.c         | 25 ++++++++++++++++---------
 2 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index e7f155c3045e..ee1a87782b2c 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -349,6 +349,11 @@ static inline int mmap_is_ia32(void)
 		test_thread_flag(TIF_ADDR32));
 }
 
+#ifdef CONFIG_COMPAT
+extern unsigned long arch_compat_rnd(void);
+#endif
+extern unsigned long arch_native_rnd(void);
+
 /* Do not change the values. See get_align_mask() */
 enum align_flags {
 	ALIGN_VA_32	= BIT(0),
diff --git a/arch/x86/mm/mmap.c b/arch/x86/mm/mmap.c
index d2dc0438d654..0b2007b08194 100644
--- a/arch/x86/mm/mmap.c
+++ b/arch/x86/mm/mmap.c
@@ -65,20 +65,27 @@ static int mmap_is_legacy(void)
 	return sysctl_legacy_va_layout;
 }
 
-unsigned long arch_mmap_rnd(void)
+#ifdef CONFIG_COMPAT
+unsigned long arch_compat_rnd(void)
 {
-	unsigned long rnd;
+	return (get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1))
+		<< PAGE_SHIFT;
+}
+#endif
 
-	if (mmap_is_ia32())
+unsigned long arch_native_rnd(void)
+{
+	return (get_random_long() & ((1UL << mmap_rnd_bits) - 1)) << PAGE_SHIFT;
+}
+
+unsigned long arch_mmap_rnd(void)
+{
 #ifdef CONFIG_COMPAT
-		rnd = get_random_long() & ((1UL << mmap_rnd_compat_bits) - 1);
-#else
-		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
+	if (mmap_is_ia32())
+		return arch_compat_rnd();
 #endif
-	else
-		rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
 
-	return rnd << PAGE_SHIFT;
+	return arch_native_rnd();
 }
 
 static unsigned long mmap_base(unsigned long rnd)
-- 
2.11.0