Messages in this thread | | | Date | Wed, 10 Sep 2014 09:20:21 -0400 | From | Vivek Goyal <> | Subject | Re: [PATCH 1/4] kaslr: check user's config too when handle relocations |
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On Wed, Sep 10, 2014 at 02:10:35PM +0800, Baoquan He wrote:
[..] > > > 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; > > > + > > > > I still think this needs a test for the 32-bit case, since IUIC, it > > requires relocations unconditionally. > > Oops, just understood that 32 bit kernel alwasy need relocations, but > only focus on x86_64 and kaslr again when I was doing it. You are right, > this is not correct for 32 bit kernel. > > I am thinking if I can add a compiling condition check like below. This > only works only when x86_64 or when kaslr is compiled in. Otherwise it > wokrs as before. > > #if CONFIG_X86_64 > if (output_orig == output) > return; > #endif
Hi Bao,
I think above should work reasonably well. Also put a comment above it. Something like as follows.
/* * 32bit always requires relocations to be performed. For x86_64, * relocations need to be performed only if kaslr has chosen a * different load address then kernel was originally loaded at. * * If we are here, either kaslr is not configured in or kaslr is disabled * or kaslr has chosen not to change the load location of kernel. Don't * perform any relocations. */
Thanks Vivek
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