Commit-ID: d6cc1c3af760c1d3f6b42f6e52b08718a6207cf1 Gitweb: http://git.kernel.org/tip/d6cc1c3af760c1d3f6b42f6e52b08718a6207cf1 Author: Suresh Siddha <suresh.b.siddha@xxxxxxxxx> AuthorDate: Mon, 19 Oct 2009 06:12:04 -0700 Committer: H. Peter Anvin <hpa@xxxxxxxxx> CommitDate: Tue, 20 Oct 2009 14:46:01 +0900 x86-64: add comment for RODATA large page retainment Add a comment explaining why RODATA is aligned to 2 MB. Signed-off-by: Suresh Siddha <suresh.b.siddha@xxxxxxxxx> Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxx> --- arch/x86/kernel/vmlinux.lds.S | 13 ++++++++++++- 1 files changed, 12 insertions(+), 1 deletions(-) diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 1476379..fd2dabe 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/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 \ -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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