On Fri, Sep 23, 2016 at 6:35 PM, Catalin Marinas <catalin.mari...@arm.com> wrote: > On Fri, Sep 23, 2016 at 09:42:30AM +0530, Pratyush Anand wrote: >> On 22/09/2016:05:50:30 PM, Catalin Marinas wrote: >> > On Thu, Sep 22, 2016 at 08:53:28AM +0530, Pratyush Anand wrote: >> > > On 21/09/2016:06:04:04 PM, Catalin Marinas wrote:
>> > As a quick workaround you could check mm->task_size > TASK_SIZE_32 in >> > the arch_uprobe_analyze_insn() function. >> >> It would be doable. TASK_SIZE_32 is defined only for COMPAT. So, may be I can >> return -EINVAL when mm->task_size < TASK_SIZE_64. > > That's just a temporary workaround. If we ever merge ILP32, this test > would no longer be enough (as the ISA is AArch64 but with TASK_SIZE_32). OK.. So what about doing something similar what x86 is doing. We can have a flag for task Type in arch specific mm_context_t. We also set this flag in COMPAT_SET_PERSONALITY() along with setting thread_info flag, and we clear them in SET_PERSONALITY(). > > Looking at prepare_uprobe(), we have a weak is_trap_insn() function. > This check is meaningless without knowing which instruction set we > target. A false positive here, however, is not that bad as we wouldn't > end up inserting the wrong breakpoint in the executable. But it looks to > me like the core uprobe code needs to pass some additional information > like the type of task or ELF format to the arch code to make a useful > choice of breakpoint type. It seems that 'strtle r0, [r0], #160' would have the closest matching aarch32 instruction wrt BRK64_OPCODE_UPROBES(0xd42000A0). But that too seems a bad instruction. So, may be we can use still weak is_trap_insn(). ~Pratyush
