On 09/05/14 at 10:11am, Kees Cook wrote: > I don't think this is correct. If you look at a02150610776 ("x86, > relocs: Move ELF relocation handling to C"), we always did relocations > on 32-bit when CONFIG_RELOCATABLE was set, so I think this will fail > badly on 32-bit. 64-bit only needs relocation when > CONFIG_RANDOMIZE_BASE is set, so this is probably what needs to be > tested here instead. I think a better option would be, in > decompress_kernel(), to compare output before and after > choose_kernel_location(). If it's the same on 64-bit, > handle_relocations() can be skipped. (Perhaps pass the before/after to > handle_relocations() and it can perform the logic.) > > -Kees
Hi Kees, Checking handle_relocations() again, I just didn't notice it's mandatory to do the relocations handling in i386. So in this function delta is checked to see if it's a kaslr relocation handling. This might be a little confusing. But I am fine with it. Per your comment, you prefer to compare the output before and after choose_kernel_location(). That's also good, Lu Yinghai posted a draft patch in this way before, however the checking and the delta calculation are not correct. I changed that and test all cases, it works well. So do you like this it? If yes I will repost it. >From 13471bd838c52a0e143c2aee81e3863cfff585bd Mon Sep 17 00:00:00 2001 From: Baoquan He <b...@redhat.com> Date: Mon, 25 Aug 2014 14:57:43 +0800 Subject: [PATCH] kaslr: check if kernel location is changed Signed-off-by: Baoquan He <b...@redhat.com> --- arch/x86/boot/compressed/misc.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) diff --git a/arch/x86/boot/compressed/misc.c b/arch/x86/boot/compressed/misc.c index 57ab74d..887f404 100644 --- a/arch/x86/boot/compressed/misc.c +++ b/arch/x86/boot/compressed/misc.c @@ -230,8 +230,9 @@ static void error(char *x) asm("hlt"); } -#if CONFIG_X86_NEED_RELOCS -static void handle_relocations(void *output, unsigned long output_len) +#ifdef CONFIG_X86_NEED_RELOCS +static void handle_relocations(void *output_orig, void *output, + unsigned long output_len) { int *reloc; unsigned long delta, map, ptr; @@ -242,6 +243,9 @@ static void handle_relocations(void *output, unsigned long output_len) * Calculate the delta between where vmlinux was linked to load * and where it was actually loaded. */ + if (output_orig == output) + return; + delta = min_addr - LOAD_PHYSICAL_ADDR; if (!delta) { debug_putstr("No relocation needed... "); @@ -299,7 +303,8 @@ static void handle_relocations(void *output, unsigned long output_len) #endif } #else -static inline void handle_relocations(void *output, unsigned long output_len) +static inline void handle_relocations(void *output_orig, void *output, + unsigned long output_len) { } #endif @@ -360,6 +365,8 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap, unsigned char *output, unsigned long output_len) { + unsigned char *output_orig = output; + real_mode = rmode; sanitize_boot_params(real_mode); @@ -402,7 +409,7 @@ asmlinkage __visible void *decompress_kernel(void *rmode, memptr heap, debug_putstr("\nDecompressing Linux... "); decompress(input_data, input_len, NULL, NULL, output, NULL, error); parse_elf(output); - handle_relocations(output, output_len); + handle_relocations(output_orig, output, output_len); debug_putstr("done.\nBooting the kernel.\n"); return output; } -- 1.8.5.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/