On 11/13/17 4:59 AM, Oleg Nesterov wrote:
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,
Will make this change in the next revision.
+ 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; +#endifOK, but shouldn't we also return ENOSYS if CONFIG_X86_64=y but the probed task is 32bit?
Just tested with a 32bit app on x86 box and segfaults. Yes, we would need to return ENOSYS if the app is 32bit on 64bit system. I may not
be worthwhile to emulate this uncommon case. I will use mmap_is_ia32 or a variant to test whether the app is 32bit or not. Please let me know whether this is correct approach or not.
Or in this case uprobe_init_insn(x86_64 => false) should fail and push_setup_xol_ops() won't be called? Oleg.
