Re: [PATCH V4 2/7] powerpc/mm: Enable ARCH_HAS_VM_GET_PAGE_PROT

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Le 08/04/2022 à 14:53, Christophe Leroy a écrit :


Le 07/04/2022 à 12:32, Anshuman Khandual a écrit :
This defines and exports a platform specific custom vm_get_page_prot() via
subscribing ARCH_HAS_VM_GET_PAGE_PROT. While here, this also localizes
arch_vm_get_page_prot() as powerpc_vm_get_page_prot() and moves it near
vm_get_page_prot().

Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
---
  arch/powerpc/Kconfig            |  1 +
  arch/powerpc/include/asm/mman.h | 12 ------------
  arch/powerpc/mm/mmap.c          | 26 ++++++++++++++++++++++++++
  3 files changed, 27 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 174edabb74fa..eb9b6ddbf92f 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -140,6 +140,7 @@ config PPC
      select ARCH_HAS_TICK_BROADCAST        if GENERIC_CLOCKEVENTS_BROADCAST
      select ARCH_HAS_UACCESS_FLUSHCACHE
      select ARCH_HAS_UBSAN_SANITIZE_ALL
+    select ARCH_HAS_VM_GET_PAGE_PROT
      select ARCH_HAVE_NMI_SAFE_CMPXCHG
      select ARCH_KEEP_MEMBLOCK
      select ARCH_MIGHT_HAVE_PC_PARPORT
diff --git a/arch/powerpc/include/asm/mman.h b/arch/powerpc/include/asm/mman.h
index 7cb6d18f5cd6..1b024e64c8ec 100644
--- a/arch/powerpc/include/asm/mman.h
+++ b/arch/powerpc/include/asm/mman.h
@@ -24,18 +24,6 @@ static inline unsigned long arch_calc_vm_prot_bits(unsigned long prot,
  }
  #define arch_calc_vm_prot_bits(prot, pkey) arch_calc_vm_prot_bits(prot, pkey)
-static inline pgprot_t arch_vm_get_page_prot(unsigned long vm_flags)
-{
-#ifdef CONFIG_PPC_MEM_KEYS
-    return (vm_flags & VM_SAO) ?
-        __pgprot(_PAGE_SAO | vmflag_to_pte_pkey_bits(vm_flags)) :
-        __pgprot(0 | vmflag_to_pte_pkey_bits(vm_flags));
-#else
-    return (vm_flags & VM_SAO) ? __pgprot(_PAGE_SAO) : __pgprot(0);
-#endif
-}
-#define arch_vm_get_page_prot(vm_flags) arch_vm_get_page_prot(vm_flags)
-
  static inline bool arch_validate_prot(unsigned long prot, unsigned long addr)
  {
      if (prot & ~(PROT_READ | PROT_WRITE | PROT_EXEC | PROT_SEM | PROT_SAO))
diff --git a/arch/powerpc/mm/mmap.c b/arch/powerpc/mm/mmap.c
index c475cf810aa8..cd17bd6fa36b 100644
--- a/arch/powerpc/mm/mmap.c
+++ b/arch/powerpc/mm/mmap.c
@@ -254,3 +254,29 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
          mm->get_unmapped_area = arch_get_unmapped_area_topdown;
      }
  }
+
+#ifdef CONFIG_PPC64
+static pgprot_t powerpc_vm_get_page_prot(unsigned long vm_flags)
+{
+#ifdef CONFIG_PPC_MEM_KEYS
+    return (vm_flags & VM_SAO) ?
+        __pgprot(_PAGE_SAO | vmflag_to_pte_pkey_bits(vm_flags)) :
+        __pgprot(0 | vmflag_to_pte_pkey_bits(vm_flags));
+#else
+    return (vm_flags & VM_SAO) ? __pgprot(_PAGE_SAO) : __pgprot(0);
+#endif
+}
+#else
+static pgprot_t powerpc_vm_get_page_prot(unsigned long vm_flags)
+{
+    return __pgprot(0);
+}
+#endif /* CONFIG_PPC64 */

Can we reduce this forest of #ifdefs and make it more readable ?

mm/mmap.c is going away with patch https://patchwork.ozlabs.org/project/linuxppc-dev/patch/d6d849621f821af253e777a24eda4c648814a76e.1646847562.git.christophe.leroy@xxxxxxxxxx/

So it would be better to add two versions of vm_get_page_prot(), for instance one in mm/pgtable_64.c and one in mm/pgtable_32.c

Indeed, you don't need anything at all for PPC32. All you need to do is

	select ARCH_HAS_VM_GET_PAGE_PROT if PPC64

And in fact it could even be PPC_BOOK3S_64 instead of PPC64 because CONFIG_PPC_MEM_KEYS depends on PPC_BOOK3S_64 and _PAGE_SAO is 0 on nohash/64.

So you can then put it into arch/powerpc/mm/book3s64/pgtable.c




+
+pgprot_t vm_get_page_prot(unsigned long vm_flags)
+{
+    return __pgprot(pgprot_val(protection_map[vm_flags &
+            (VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)]) |
+           pgprot_val(powerpc_vm_get_page_prot(vm_flags)));
+}
+EXPORT_SYMBOL(vm_get_page_prot);

By the way I'm a bit puzzled with the name powerpc_vm_get_page_prot(), the name suggests that it's just a powerpc replacement of vm_get_page_prot(). I'd prefer if it was named __vm_get_page_prot(), it would be clearer that it is a complement to vm_get_page_prot() and not a remplacement.

Christophe



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