Messages in this thread | | | Date | Mon, 13 Nov 2017 13:59:56 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH][v2] uprobes/x86: emulate push insns for uprobe on x86 |
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The patch looks good to me, but I have a question because I know nothing about insn encoding,
On 11/10, Yonghong Song wrote: > > +static int push_setup_xol_ops(struct arch_uprobe *auprobe, struct insn *insn) > +{ > + u8 opc1 = OPCODE1(insn), reg_offset = 0; > + > + if (opc1 < 0x50 || opc1 > 0x57) > + return -ENOSYS; > + > + if (insn->length > 2) > + return -ENOSYS; > + if (insn->length == 2) { > + /* only support rex_prefix 0x41 (x64 only) */ > +#ifdef CONFIG_X86_64 > + if (insn->rex_prefix.nbytes != 1 || > + insn->rex_prefix.bytes[0] != 0x41) > + return -ENOSYS; > + > + auprobe->push.ilen = 2;
and the "else" branch does
auprobe->push.ilen = 1;
you could add auprobe->push.ilen = insn->length;
at the end of push_setup_xol_ops() instead, but this is minor/cosmetic,
> + switch (opc1) { > + case 0x50: > + reg_offset = offsetof(struct pt_regs, r8); > + break; > + case 0x51: > + reg_offset = offsetof(struct pt_regs, r9); > + break; > + case 0x52: > + reg_offset = offsetof(struct pt_regs, r10); > + break; > + case 0x53: > + reg_offset = offsetof(struct pt_regs, r11); > + break; > + case 0x54: > + reg_offset = offsetof(struct pt_regs, r12); > + break; > + case 0x55: > + reg_offset = offsetof(struct pt_regs, r13); > + break; > + case 0x56: > + reg_offset = offsetof(struct pt_regs, r14); > + break; > + case 0x57: > + reg_offset = offsetof(struct pt_regs, r15); > + break; > + } > +#else > + return -ENOSYS; > +#endif
OK, but shouldn't we also return ENOSYS if CONFIG_X86_64=y but the probed task is 32bit?
Or in this case uprobe_init_insn(x86_64 => false) should fail and push_setup_xol_ops() won't be called?
Oleg.
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