Messages in this thread | | | Date | Thu, 07 Nov 2013 00:31:55 +0800 | From | Jiang Liu <> | Subject | Re: [PATCH v5 4/7] arm64: introduce aarch64_insn_gen_{nop|branch_imm}() helper functions |
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On 10/30/2013 08:48 AM, Will Deacon wrote: > On Fri, Oct 18, 2013 at 04:19:58PM +0100, Jiang Liu wrote: >> From: Jiang Liu <jiang.liu@huawei.com> >> >> Introduce aarch64_insn_gen_{nop|branch_imm}() helper functions, which >> will be used to implement jump label on ARM64. >> >> Signed-off-by: Jiang Liu <jiang.liu@huawei.com> >> Cc: Jiang Liu <liuj97@gmail.com> >> --- >> arch/arm64/include/asm/insn.h | 13 +++++++++++++ >> arch/arm64/kernel/insn.c | 28 ++++++++++++++++++++++++++++ >> 2 files changed, 41 insertions(+) >> >> diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h >> index 8f94e48..ee4a60d 100644 >> --- a/arch/arm64/include/asm/insn.h >> +++ b/arch/arm64/include/asm/insn.h >> @@ -96,9 +96,22 @@ static __always_inline void aarch64_insn_write(void *addr, u32 insn) >> *(u32 *)addr = cpu_to_le32(insn); >> } >> >> +static __always_inline u32 aarch64_insn_gen_hint(enum aarch64_insn_hint_op op) >> +{ >> + return aarch64_insn_get_hint_value() | op; > > What's the point in that helper function? Does it just return an immediate > value (and are there are other users of it?). It just returns a const value. The helper function is just for ease maintainence.
> >> +} >> + >> +static __always_inline u32 aarch64_insn_gen_nop(void) >> +{ >> + return aarch64_insn_gen_hint(AARCH64_INSN_HINT_NOP); >> +} > > Either use plain old `inline' or write these as preprocessor macros. Will change to normal (non-inline) and add __kprobe property.
> >> + >> enum aarch64_insn_encoding_class aarch64_get_insn_class(u32 insn); >> u32 aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type, >> u32 insn, u64 imm); >> +u32 aarch64_insn_gen_branch_imm(unsigned long pc, unsigned long addr, >> + bool link); >> + >> bool aarch64_insn_hotpatch_safe(u32 old_insn, u32 new_insn); >> >> int aarch64_insn_patch_text_nosync(void *addr, u32 insn); >> diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c >> index 886821f..f7498cc 100644 >> --- a/arch/arm64/kernel/insn.c >> +++ b/arch/arm64/kernel/insn.c >> @@ -14,6 +14,7 @@ >> * You should have received a copy of the GNU General Public License >> * along with this program. If not, see <http://www.gnu.org/licenses/>. >> */ >> +#include <linux/bitops.h> >> #include <linux/compiler.h> >> #include <linux/kernel.h> >> #include <linux/smp.h> >> @@ -233,3 +234,30 @@ u32 aarch64_insn_encode_immediate(enum aarch64_insn_imm_type type, >> >> return insn; >> } >> + >> +u32 aarch64_insn_gen_branch_imm(unsigned long pc, unsigned long addr, bool link) >> +{ >> + u32 insn; >> + long offset; >> + >> + /* >> + * PC: A 64-bit Program Counter holding the address of the current >> + * instruction. A64 instructions may be word-aligned. >> + */ >> + BUG_ON((pc & 0x3) || (addr & 0x3)); >> + >> + /* >> + * B/BL support [-128M, 128M) offset >> + * ARM64 virtual address arrangement garantees all kernel and module > > Typo: `guarantees'. Thanks, will fix it.
> >> + * texts are within +/-128M. >> + */ >> + offset = ((long)addr - (long)pc) >> 2; >> + BUG_ON(abs(offset) > BIT(25) || offset == BIT(25)); > > I really struggle to follow this range checking. Why don't you just compare > the absolute difference between addr and pc with SZ_128M? Will change code to follow your suggestion.
> > Will >
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