mm/vma: add vma_flags_empty(), vma_flags_and(), vma_flags_diff_pair()

Patch series "mm/vma: convert vm_flags_t to vma_flags_t in vma code", v4.

This series converts a lot of the existing use of the legacy vm_flags_t
data type to the new vma_flags_t type which replaces it.

In order to do so it adds a number of additional helpers:

* vma_flags_empty() - Determines whether a vma_flags_t value has no bits
  set.

* vma_flags_and() - Performs a bitwise AND between two vma_flags_t values.

* vma_flags_diff_pair() - Determines which flags are not shared between a
  pair of VMA flags (typically non-constant values)

* append_vma_flags() - Similar to mk_vma_flags(), but allows a vma_flags_t
  value to be specified (typically a constant value) which will be copied
  and appended to to create a new vma_flags_t value, with additional flags
  specified to append to it.

* vma_flags_same() - Determines if a vma_flags_t value is exactly equal to
  a set of VMA flags.

* vma_flags_same_mask() - Determines if a vma_flags_t value is eactly equal
  to another vma_flags_t value (typically constant).

* vma_flags_same_pair() - Determines if a pair of vma_flags_t values are
  exactly equal to one another (typically both non-constant).

* vma_flags_to_legacy() - Converts a vma_flags_t value to a vm_flags_t
  value, used to enable more iterative introduction of the use of
  vma_flags_t.

* legacy_to_vma_flags() - Converts a vm_flags_t value to a vma_flags-t
  value, for the same purpose.

* vma_flags_test_single_mask() - Tests whether a vma_flags_t value contain
  the single flag specified in an input vma_flags_t flag mask, or if that
  flag mask is empty, is defined to return false. Useful for
  config-predicated VMA flag mask defines.

* vma_test() - Tests whether a VMA's flags contain a specific singular VMA
  flag.

* vma_test_any() - Tests whether a VMA's flags contain any of a set of VMA
  flags.

* vma_test_any_mask() - Tests whether a VMA's flags contain any of the
  flags specified in another, typically constant, vma_flags_t value.

* vma_test_single_mask() - Tests whether a VMA's flags contain the single
  flag specified in an input vma_flags_t flag mask, or if that flag mask is
  empty, is defined to return false. Useful for config-predicated VMA flag
  mask defines.

* vma_clear_flags() - Clears a specific set of VMA flags from a vma_flags_t
  value.

* vma_clear_flags_mask() - Clears those flag set in a vma_flags_t value
  (typically constant) from a (typically not constant) vma_flags_t value.

The series mostly focuses on the the VMA specific code, especially that
contained in mm/vma.c and mm/vma.h.

It updates both brk() and mmap() logic to utils vma_flags_t values as much
as is practiaclly possible at this point, changing surrounding logic to be
able to do so.

It also updates the vma_modify_xxx() functions where they interact with VMA
flags directly to use vm_flags_t values where possible.

There is extensive testing added in the VMA userland tests to assert that
all of these new VMA flag functions work correctly.


This patch (of 25):

Firstly, add the ability to determine if VMA flags are empty, that is no
flags are set in a vma_flags_t value.

Next, add the ability to obtain the equivalent of the bitwise and of two
vma_flags_t values, via vma_flags_and_mask().

Next, add the ability to obtain the difference between two sets of VMA
flags, that is the equivalent to the exclusive bitwise OR of the two sets
of flags, via vma_flags_diff_pair().

vma_flags_xxx_mask() typically operates on a pointer to a vma_flags_t
value, which is assumed to be an lvalue of some kind (such as a field in a
struct or a stack variable) and an rvalue of some kind (typically a
constant set of VMA flags obtained e.g.  via mk_vma_flags() or
equivalent).

However vma_flags_diff_pair() is intended to operate on two lvalues, so
use the _pair() suffix to make this clear.

Finally, update VMA userland tests to add these helpers.

We also port bitmap_xor() and __bitmap_xor() to the tools/ headers and
source to allow the tests to work with vma_flags_diff_pair().

Link: https://lkml.kernel.org/r/cover.1774034900.git.ljs@kernel.org
Link: https://lkml.kernel.org/r/53ab55b7da91425775e42c03177498ad6de88ef4.1774034900.git.ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Ondrej Mosnacek <omosnace@redhat.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Richard Weinberger <richard@nod.at>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Cc: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2 files changed, 59 insertions, 9 deletions

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 16a1ad9a3397..7954a7a2b811 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1049,6 +1049,19 @@ static __always_inline vma_flags_t __mk_vma_flags(size_t count,
 }
 
 /*
+ * Helper macro which bitwise-or combines the specified input flags into a
+ * vma_flags_t bitmap value. E.g.:
+ *
+ * vma_flags_t flags = mk_vma_flags(VMA_IO_BIT, VMA_PFNMAP_BIT,
+ *              VMA_DONTEXPAND_BIT, VMA_DONTDUMP_BIT);
+ *
+ * The compiler cleverly optimises away all of the work and this ends up being
+ * equivalent to aggregating the values manually.
+ */
+#define mk_vma_flags(...) __mk_vma_flags(COUNT_ARGS(__VA_ARGS__), \
+					 (const vma_flag_t []){__VA_ARGS__})
+
+/*
  * Test whether a specific VMA flag is set, e.g.:
  *
  * if (vma_flags_test(flags, VMA_READ_BIT)) { ... }
@@ -1062,17 +1075,30 @@ static __always_inline bool vma_flags_test(const vma_flags_t *flags,
 }
 
 /*
- * Helper macro which bitwise-or combines the specified input flags into a
- * vma_flags_t bitmap value. E.g.:
- *
- * vma_flags_t flags = mk_vma_flags(VMA_IO_BIT, VMA_PFNMAP_BIT,
- * 		VMA_DONTEXPAND_BIT, VMA_DONTDUMP_BIT);
+ * Obtain a set of VMA flags which contain the overlapping flags contained
+ * within flags and to_and.
+ */
+static __always_inline vma_flags_t vma_flags_and_mask(const vma_flags_t *flags,
+						      vma_flags_t to_and)
+{
+	vma_flags_t dst;
+	unsigned long *bitmap_dst = dst.__vma_flags;
+	const unsigned long *bitmap = flags->__vma_flags;
+	const unsigned long *bitmap_to_and = to_and.__vma_flags;
+
+	bitmap_and(bitmap_dst, bitmap, bitmap_to_and, NUM_VMA_FLAG_BITS);
+	return dst;
+}
+
+/*
+ * Obtain a set of VMA flags which contains the specified overlapping flags,
+ * e.g.:
  *
- * The compiler cleverly optimises away all of the work and this ends up being
- * equivalent to aggregating the values manually.
+ * vma_flags_t read_flags = vma_flags_and(&flags, VMA_READ_BIT,
+ *                                        VMA_MAY_READ_BIT);
  */
-#define mk_vma_flags(...) __mk_vma_flags(COUNT_ARGS(__VA_ARGS__), \
-					 (const vma_flag_t []){__VA_ARGS__})
+#define vma_flags_and(flags, ...)				\
+	vma_flags_and_mask(flags, mk_vma_flags(__VA_ARGS__))
 
 /*  Test each of to_test flags in flags, non-atomically. */
 static __always_inline bool vma_flags_test_any_mask(const vma_flags_t *flags,
@@ -1147,6 +1173,22 @@ static __always_inline void vma_flags_clear_mask(vma_flags_t *flags,
 	vma_flags_clear_mask(flags, mk_vma_flags(__VA_ARGS__))
 
 /*
+ * Obtain a VMA flags value containing those flags that are present in flags or
+ * flags_other but not in both.
+ */
+static __always_inline vma_flags_t vma_flags_diff_pair(const vma_flags_t *flags,
+		const vma_flags_t *flags_other)
+{
+	vma_flags_t dst;
+	const unsigned long *bitmap_other = flags_other->__vma_flags;
+	const unsigned long *bitmap = flags->__vma_flags;
+	unsigned long *bitmap_dst = dst.__vma_flags;
+
+	bitmap_xor(bitmap_dst, bitmap, bitmap_other, NUM_VMA_FLAG_BITS);
+	return dst;
+}
+
+/*
  * Helper to test that ALL specified flags are set in a VMA.
  *
  * Note: appropriate locks must be held, this function does not acquire them for
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index f22aecb047b7..321aa150c1ee 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -870,6 +870,14 @@ typedef struct {
 
 #define EMPTY_VMA_FLAGS ((vma_flags_t){ })
 
+/* Are no flags set in the specified VMA flags? */
+static __always_inline bool vma_flags_empty(const vma_flags_t *flags)
+{
+	const unsigned long *bitmap = flags->__vma_flags;
+
+	return bitmap_empty(bitmap, NUM_VMA_FLAG_BITS);
+}
+
 /*
  * Describes a VMA that is about to be mmap()'ed. Drivers may choose to
  * manipulate mutable fields which will cause those fields to be updated in the