Messages in this thread | | | Date | Thu, 19 Nov 2020 13:36:36 +0100 | From | Thomas Bogendoerfer <> | Subject | Re: [PATCH 1/3] MIPS: KASLR: Correcte valid bits in apply_r_mips_26_rel |
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On Thu, Nov 19, 2020 at 10:29:12AM +0800, Jinyang He wrote: > Apply_r_mips_26_rel() relocates instructions like j, jal and etc. These > instructions consist of 6bits function field and 26bits address field. > The value of target_addr as follows, > ================================================================= > | high 4bits | low 28bits | > ================================================================= > |the high 4bits of this PC | the low 26bits of instructions << 2| > ================================================================= > Thus, loc_orig and log_new both need high 4bits ranther than high 6bits. rather
> Replace 0x3ffffff with 0xfffffff. > > Signed-off-by: Jinyang He <hejinyang@loongson.cn> > --- > arch/mips/kernel/relocate.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/arch/mips/kernel/relocate.c b/arch/mips/kernel/relocate.c > index 3d80a51..709cfa0 100644 > --- a/arch/mips/kernel/relocate.c > +++ b/arch/mips/kernel/relocate.c > @@ -95,7 +95,7 @@ static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset) > > /* Original target address */ > target_addr <<= 2; > - target_addr += (unsigned long)loc_orig & ~0x03ffffff; > + target_addr += (unsigned long)loc_orig & ~0x0fffffff;
how about using
target_addr += (unsigned long)log_orig & 0xf0000000;
which makes it IMHO even clearer what this does ?
Thomas.
-- Crap can work. Given enough thrust pigs will fly, but it's not necessarily a good idea. [ RFC1925, 2.3 ]
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