From 74e081797bd9d2a7d8005fe519e719df343a2ba8 Mon Sep 17 00:00:00 2001 From: Suresh Siddha Date: Wed, 14 Oct 2009 14:46:56 -0700 Subject: x86-64: align RODATA kernel section to 2MB with CONFIG_DEBUG_RODATA CONFIG_DEBUG_RODATA chops the large pages spanning boundaries of kernel text/rodata/data to small 4KB pages as they are mapped with different attributes (text as RO, RODATA as RO and NX etc). On x86_64, preserve the large page mappings for kernel text/rodata/data boundaries when CONFIG_DEBUG_RODATA is enabled. This is done by allowing the RODATA section to be hugepage aligned and having same RWX attributes for the 2MB page boundaries Extra Memory pages padding the sections will be freed during the end of the boot and the kernel identity mappings will have different RWX permissions compared to the kernel text mappings. Kernel identity mappings to these physical pages will be mapped with smaller pages but large page mappings are still retained for kernel text,rodata,data mappings. Signed-off-by: Suresh Siddha LKML-Reference: <20091014220254.190119924@sbs-t61.sc.intel.com> Signed-off-by: H. Peter Anvin --- arch/x86/mm/pageattr.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) (limited to 'arch/x86/mm/pageattr.c') diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index dd38bfbefd1f..b494fc4a986e 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -279,6 +279,20 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long address, __pa((unsigned long)__end_rodata) >> PAGE_SHIFT)) pgprot_val(forbidden) |= _PAGE_RW; +#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) + /* + * Kernel text mappings for the large page aligned .rodata section + * will be read-only. For the kernel identity mappings covering + * the holes caused by this alignment can be anything. + * + * This will preserve the large page mappings for kernel text/data + * at no extra cost. + */ + if (within(address, (unsigned long)_text, + (unsigned long)__end_rodata_hpage_align)) + pgprot_val(forbidden) |= _PAGE_RW; +#endif + prot = __pgprot(pgprot_val(prot) & ~pgprot_val(forbidden)); return prot; -- cgit v1.2.3