linux-kernel - [PATCH] mm: provide a fallback for PAGE_KERNEL

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Message-Id: <20180428001526.22475-1-mcgrof@kernel.org>
Date:   Fri, 27 Apr 2018 17:15:26 -0700
From:   "Luis R. Rodriguez" <mcgrof@...nel.org>
To:     arnd@...db.de
Cc:     gregkh@...uxfoundation.org, linux-arch@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Luis R. Rodriguez" <mcgrof@...nel.org>
Subject: [PATCH] mm: provide a fallback for PAGE_KERNEL_RO for architectures

Some architectures do not define PAGE_KERNEL_RO, best we can do
for them is to provide a fallback onto PAGE_KERNEL. Remove the
hack from the firmware loader and move it onto the asm-generic
header, and document while at it the affected architectures
which do not have a PAGE_KERNEL_RO:

  o alpha
  o ia64
  o m68k
  o mips
  o sparc64
  o sparc

Blessed-by: 0-day
Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
---
 drivers/base/firmware_loader/fallback.c |  5 -----
 include/asm-generic/pgtable.h           | 15 +++++++++++++++
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
index 31b5015b59fe..90f36be9e5ca 100644
--- a/drivers/base/firmware_loader/fallback.c
+++ b/drivers/base/firmware_loader/fallback.c
@@ -219,11 +219,6 @@ static ssize_t firmware_loading_show(struct device *dev,
 	return sprintf(buf, "%d\n", loading);
 }
 
-/* Some architectures don't have PAGE_KERNEL_RO */
-#ifndef PAGE_KERNEL_RO
-#define PAGE_KERNEL_RO PAGE_KERNEL
-#endif
-
 /* one pages buffer should be mapped/unmapped only once */
 static int map_fw_priv_pages(struct fw_priv *fw_priv)
 {
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index f59639afaa39..da47fe81df51 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -1083,6 +1083,21 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
 static inline void init_espfix_bsp(void) { }
 #endif
 
+/*
+ * Some architectures don't have PAGE_KERNEL_RO. This is the best
+ * we can do for them buggers for now. Currently known to not have it:
+ *
+ *  o alpha
+ *  o ia64
+ *  o m68k
+ *  o mips
+ *  o sparc64
+ *  o sparc
+ */
+#ifndef PAGE_KERNEL_RO
+#define PAGE_KERNEL_RO PAGE_KERNEL
+#endif
+
 #endif /* !__ASSEMBLY__ */
 
 #ifndef io_remap_pfn_range
-- 
2.13.2