On Sun, Jan 03, 2016 at 05:05:57PM +0100, Ard Biesheuvel wrote: > Instead of using absolute addresses for both the exception location > and the fixup, use offsets relative to the exception table entry values. > Not only does this cut the size of the exception table in half, it is > also a prerequisite for KASLR, since absolute exception table entries > are subject to dynamic relocation, which is incompatible with the sorting > of the exception table that occurs at build time. > > Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > Cc: Will Deacon <will.deacon@xxxxxxx> > Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx> > --- > > Note that this patch supersedes the version I sent as part of the series that > implements KASLR for arm64: http://thread.gmane.org/gmane.linux.kernel/2116531 > > arch/arm64/include/asm/assembler.h | 2 +- > arch/arm64/include/asm/futex.h | 4 ++-- > arch/arm64/include/asm/uaccess.h | 18 ++++++++++-------- > arch/arm64/kernel/armv8_deprecated.c | 4 ++-- > arch/arm64/mm/extable.c | 2 +- > scripts/sortextable.c | 2 +- > 6 files changed, 17 insertions(+), 15 deletions(-) This looks good to me, so for the arm64 part (i.e. this patch): Acked-by: Will Deacon <will.deacon@xxxxxxx> Will > diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h > index 12eff928ef8b..8094d50f05bc 100644 > --- a/arch/arm64/include/asm/assembler.h > +++ b/arch/arm64/include/asm/assembler.h > @@ -98,7 +98,7 @@ > 9999: x; \ > .section __ex_table,"a"; \ > .align 3; \ > - .quad 9999b,l; \ > + .long (9999b - .), (l - .); \ > .previous > > /* > diff --git a/arch/arm64/include/asm/futex.h b/arch/arm64/include/asm/futex.h > index 007a69fc4f40..35e73e255ad3 100644 > --- a/arch/arm64/include/asm/futex.h > +++ b/arch/arm64/include/asm/futex.h > @@ -44,7 +44,7 @@ > " .popsection\n" \ > " .pushsection __ex_table,\"a\"\n" \ > " .align 3\n" \ > -" .quad 1b, 4b, 2b, 4b\n" \ > +" .long (1b - .), (4b - .), (2b - .), (4b - .)\n" \ > " .popsection\n" \ > ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, \ > CONFIG_ARM64_PAN) \ > @@ -135,7 +135,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, > " .popsection\n" > " .pushsection __ex_table,\"a\"\n" > " .align 3\n" > -" .quad 1b, 4b, 2b, 4b\n" > +" .long (1b - .), (4b - .), (2b - .), (4b - .)\n" > " .popsection\n" > : "+r" (ret), "=&r" (val), "+Q" (*uaddr), "=&r" (tmp) > : "r" (oldval), "r" (newval), "Ir" (-EFAULT) > diff --git a/arch/arm64/include/asm/uaccess.h b/arch/arm64/include/asm/uaccess.h > index b2ede967fe7d..ab627e6c06c9 100644 > --- a/arch/arm64/include/asm/uaccess.h > +++ b/arch/arm64/include/asm/uaccess.h > @@ -36,11 +36,11 @@ > #define VERIFY_WRITE 1 > > /* > - * The exception table consists of pairs of addresses: the first is the > - * address of an instruction that is allowed to fault, and the second is > - * the address at which the program should continue. No registers are > - * modified, so it is entirely up to the continuation code to figure out > - * what to do. > + * The exception table consists of pairs of relative offsets: the first > + * is the relative offset to an instruction that is allowed to fault, > + * and the second is the relative offset at which the program should > + * continue. No registers are modified, so it is entirely up to the > + * continuation code to figure out what to do. > * > * All the routines below use bits of fixup code that are out of line > * with the main instruction path. This means when everything is well, > @@ -50,9 +50,11 @@ > > struct exception_table_entry > { > - unsigned long insn, fixup; > + int insn, fixup; > }; > > +#define ARCH_HAS_RELATIVE_EXTABLE > + > extern int fixup_exception(struct pt_regs *regs); > > #define KERNEL_DS (-1UL) > @@ -125,7 +127,7 @@ static inline void set_fs(mm_segment_t fs) > " .previous\n" \ > " .section __ex_table,\"a\"\n" \ > " .align 3\n" \ > - " .quad 1b, 3b\n" \ > + " .long (1b - .), (3b - .)\n" \ > " .previous" \ > : "+r" (err), "=&r" (x) \ > : "r" (addr), "i" (-EFAULT)) > @@ -192,7 +194,7 @@ do { \ > " .previous\n" \ > " .section __ex_table,\"a\"\n" \ > " .align 3\n" \ > - " .quad 1b, 3b\n" \ > + " .long (1b - .), (3b - .)\n" \ > " .previous" \ > : "+r" (err) \ > : "r" (x), "r" (addr), "i" (-EFAULT)) > diff --git a/arch/arm64/kernel/armv8_deprecated.c b/arch/arm64/kernel/armv8_deprecated.c > index 937f5e58a4d3..8f21b1363387 100644 > --- a/arch/arm64/kernel/armv8_deprecated.c > +++ b/arch/arm64/kernel/armv8_deprecated.c > @@ -299,8 +299,8 @@ static void register_insn_emulation_sysctl(struct ctl_table *table) > " .popsection" \ > " .pushsection __ex_table,\"a\"\n" \ > " .align 3\n" \ > - " .quad 0b, 4b\n" \ > - " .quad 1b, 4b\n" \ > + " .long (0b - .), (4b - .)\n" \ > + " .long (1b - .), (4b - .)\n" \ > " .popsection\n" \ > ALTERNATIVE("nop", SET_PSTATE_PAN(1), ARM64_HAS_PAN, \ > CONFIG_ARM64_PAN) \ > diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c > index 79444279ba8c..81acd4706878 100644 > --- a/arch/arm64/mm/extable.c > +++ b/arch/arm64/mm/extable.c > @@ -11,7 +11,7 @@ int fixup_exception(struct pt_regs *regs) > > fixup = search_exception_tables(instruction_pointer(regs)); > if (fixup) > - regs->pc = fixup->fixup; > + regs->pc = (unsigned long)&fixup->fixup + fixup->fixup; > > return fixup != NULL; > } > diff --git a/scripts/sortextable.c b/scripts/sortextable.c > index c2423d913b46..af247c70fb66 100644 > --- a/scripts/sortextable.c > +++ b/scripts/sortextable.c > @@ -282,12 +282,12 @@ do_file(char const *const fname) > case EM_386: > case EM_X86_64: > case EM_S390: > + case EM_AARCH64: > custom_sort = sort_relative_table; > break; > case EM_ARCOMPACT: > case EM_ARCV2: > case EM_ARM: > - case EM_AARCH64: > case EM_MICROBLAZE: > case EM_MIPS: > case EM_XTENSA: > -- > 1.9.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-alpha" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
