| Message ID | 1605752954-10368-1-git-send-email-hejinyang@loongson.cn (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/3] MIPS: KASLR: Correcte valid bits in apply_r_mips_26_rel | expand |
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.
Hi, On 11/19/2020 08:36 PM, Thomas Bogendoerfer wrote: > 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 ? That sounds good. I'll send v2 later. Thanks, Jinyang. > Thomas. >
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; /* Get the new target address */ target_addr += offset; @@ -105,7 +105,7 @@ static int __init apply_r_mips_26_rel(u32 *loc_orig, u32 *loc_new, long offset) return -ENOEXEC; } - target_addr -= (unsigned long)loc_new & ~0x03ffffff; + target_addr -= (unsigned long)loc_new & ~0x0fffffff; target_addr >>= 2; *loc_new = (*loc_new & ~0x03ffffff) | (target_addr & 0x03ffffff);
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. 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(-)