---

yaml --- r: 173037 b: refs/heads/master c: d6cc1c3 h: refs/heads/master i: 173035: 6ff35e2 v: v3
git-mirror · Oct 20, 2009 · 84e9398 · 84e9398
1 parent dcd473f
commit 84e9398
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Showing 2 changed files with 13 additions and 2 deletions.
diff --git a/[refs] b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 74e081797bd9d2a7d8005fe519e719df343a2ba8
+refs/heads/master: d6cc1c3af760c1d3f6b42f6e52b08718a6207cf1
diff --git a/trunk/arch/x86/kernel/vmlinux.lds.S b/trunk/arch/x86/kernel/vmlinux.lds.S
@@ -42,7 +42,18 @@ jiffies_64 = jiffies;
 #endif
 
 #if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA)
-
+/*
+ * On 64-bit, align RODATA to 2MB so that even with CONFIG_DEBUG_RODATA
+ * we retain large page mappings for boundaries spanning kernel text, rodata
+ * and data sections.
+ *
+ * However, kernel identity mappings will have different RWX permissions
+ * to the pages mapping to text and to the pages padding (which are freed) the
+ * text section. Hence kernel identity mappings will be broken to smaller
+ * pages. For 64-bit, kernel text and kernel identity mappings are different,
+ * so we can enable protection checks that come with CONFIG_DEBUG_RODATA,
+ * as well as retain 2MB large page mappings for kernel text.
+ */
 #define X64_ALIGN_DEBUG_RODATA_BEGIN	. = ALIGN(HPAGE_SIZE);
 
 #define X64_ALIGN_DEBUG_RODATA_END				\