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 --- arch/x86/include/asm/sections.h | 6 ++++++ arch/x86/kernel/vmlinux.lds.S | 17 +++++++++++++++++ arch/x86/mm/init_64.c | 14 +++++++++++++- arch/x86/mm/pageattr.c | 14 ++++++++++++++ 4 files changed, 50 insertions(+), 1 deletion(-) Index: tree/arch/x86/include/asm/sections.h =================================================================== --- tree.orig/arch/x86/include/asm/sections.h +++ tree/arch/x86/include/asm/sections.h @@ -2,7 +2,13 @@ #define _ASM_X86_SECTIONS_H #include +#include extern char __brk_base[], __brk_limit[]; +extern struct exception_table_entry __stop___ex_table[]; + +#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) +extern char __end_rodata_hpage_align[]; +#endif #endif /* _ASM_X86_SECTIONS_H */ Index: tree/arch/x86/kernel/vmlinux.lds.S =================================================================== --- tree.orig/arch/x86/kernel/vmlinux.lds.S +++ tree/arch/x86/kernel/vmlinux.lds.S @@ -41,6 +41,21 @@ ENTRY(phys_startup_64) jiffies_64 = jiffies; #endif +#if defined(CONFIG_X86_64) && defined(CONFIG_DEBUG_RODATA) + +#define X64_ALIGN_DEBUG_RODATA_BEGIN . = ALIGN(HPAGE_SIZE); + +#define X64_ALIGN_DEBUG_RODATA_END \ + . = ALIGN(HPAGE_SIZE); \ + __end_rodata_hpage_align = .; + +#else + +#define X64_ALIGN_DEBUG_RODATA_BEGIN +#define X64_ALIGN_DEBUG_RODATA_END + +#endif + PHDRS { text PT_LOAD FLAGS(5); /* R_E */ data PT_LOAD FLAGS(7); /* RWE */ @@ -90,7 +105,9 @@ SECTIONS EXCEPTION_TABLE(16) :text = 0x9090 + X64_ALIGN_DEBUG_RODATA_BEGIN RO_DATA(PAGE_SIZE) + X64_ALIGN_DEBUG_RODATA_END /* Data */ .data : AT(ADDR(.data) - LOAD_OFFSET) { Index: tree/arch/x86/mm/init_64.c =================================================================== --- tree.orig/arch/x86/mm/init_64.c +++ tree/arch/x86/mm/init_64.c @@ -726,9 +726,13 @@ void set_kernel_text_ro(void) void mark_rodata_ro(void) { - unsigned long start = PFN_ALIGN(_text), end = PFN_ALIGN(__end_rodata); + unsigned long start = PFN_ALIGN(_text); unsigned long rodata_start = ((unsigned long)__start_rodata + PAGE_SIZE - 1) & PAGE_MASK; + unsigned long end = (unsigned long) &__end_rodata_hpage_align; + unsigned long text_end = PAGE_ALIGN((unsigned long) &__stop___ex_table); + unsigned long rodata_end = PAGE_ALIGN((unsigned long) &__end_rodata); + unsigned long data_start = (unsigned long) &_sdata; printk(KERN_INFO "Write protecting the kernel read-only data: %luk\n", (end - start) >> 10); @@ -751,6 +755,14 @@ void mark_rodata_ro(void) printk(KERN_INFO "Testing CPA: again\n"); set_memory_ro(start, (end-start) >> PAGE_SHIFT); #endif + + free_init_pages("unused kernel memory", + (unsigned long) page_address(virt_to_page(text_end)), + (unsigned long) + page_address(virt_to_page(rodata_start))); + free_init_pages("unused kernel memory", + (unsigned long) page_address(virt_to_page(rodata_end)), + (unsigned long) page_address(virt_to_page(data_start))); } #endif Index: tree/arch/x86/mm/pageattr.c =================================================================== --- tree.orig/arch/x86/mm/pageattr.c +++ tree/arch/x86/mm/pageattr.c @@ -279,6 +279,20 @@ static inline pgprot_t static_protection __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; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/