Messages in this thread | | | Date | Sun, 19 Jul 2009 20:09:14 -0400 | Subject | Re: [PATCH] x86: NX protection for kernel data | From | Siarhei Liakh <> |
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On Sun, Jul 19, 2009 at 4:13 PM, Sam Ravnborg<sam@ravnborg.org> wrote: > On Sun, Jul 19, 2009 at 03:43:06PM -0400, Siarhei Liakh wrote: >> This patch expands functionality of CONFIG_DEBUG_RODATA to set main >> (static) kernel data area as NX. >> The following steps are taken to achieve this: >> 1. Linker scripts are adjusted so .text always starts and end on a page boundary >> 2. Linker scripts are adjusted so .rodata and .data always starts and >> end on a page boundary >> 3. void mark_nxdata_nx(void) added to arch/x86/mm/init_64.c and >> arch/x86/mm/init_32.c with actual functionality: NX is set for all >> pages from _etext through _edata >> 4. mark_nxdata_nx() called from init_post(void) in init/main.c >> >> The patch have been developed for Linux 2.6.30 x86 by Siarhei Liakh >> <sliakh.lkml@gmail.com> and Xuxian Jiang <jiang@cs.ncsu.edu>. > > > The patch no longer applies. > The file vmlinux_32.lds.S and vmlinux_64.lds.S has been unified > into one file.
That is actually a great news. I will get the latest source and re-write the patch.
>> --- a/arch/x86/kernel/vmlinux_32.lds.S >> +++ b/arch/x86/kernel/vmlinux_32.lds.S >> @@ -47,6 +47,7 @@ SECTIONS >> IRQENTRY_TEXT >> *(.fixup) >> *(.gnu.warning) >> + . = ALIGN(PAGE_SIZE); /* .text should occupy whole number of pages */ >> _etext = .; /* End of text section */ > > So _etext cover until page boundary - makes sense. > >> } :text = 0x9090 >> >> @@ -93,6 +94,7 @@ SECTIONS >> *(.data.read_mostly) >> _edata = .; /* End of data section */ >> } >> + . = ALIGN(PAGE_SIZE); /* needed so we can set NX for .data */ > > But here _edata does not cover until page boundary. > And alignmnet is located outside the output section > definition. > It would be better/more consistent to follow the style you use for .text here.
You are correct. _edata should be the last thing in .data, and alignment should be done before it. However, this brings up a question: was there any specific reason to leave .data.init_task beyond the _edata? Should we move _edata into the the last of the .data.* sections to have poper view of kernel layout? -- 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/
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