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Commit d6cc1c3a authored by Suresh Siddha's avatar Suresh Siddha Committed by H. Peter Anvin
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x86-64: add comment for RODATA large page retainment 



Add a comment explaining why RODATA is aligned to 2 MB.

Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
parent 74e08179

arch/x86/kernel/vmlinux.lds.S

+12 −1
Original line number Diff line number Diff line
@@ -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				\