Hello Tony, Thank you for review. Luck, Tony wrote: > +/* Insert a long branch code */ > +static void __kprobes set_brl_inst(void *from, void *to) > +{ > + s64 rel = ((s64) to - (s64) from) >> 4; > + bundle_t *brl; > + brl = (bundle_t *) ((u64) from & ~0xf); > + brl->quad0.template = 0x05; /* [MLX](stop) */ > + brl->quad0.slot0 = NOP_M_INST; /* nop.m 0x0 */ > + brl->quad0.slot1_p0 = ((rel >> 20) & 0x7fffffffff) << 2; > + brl->quad1.slot1_p1 = (((rel >> 20) & 0x7fffffffff) << 2) >> (64 - 46); > + /* brl.cond.sptk.many.clr rel<<4 (qp=0) */ > + brl->quad1.slot2 = BRL_INST(rel >> 59, rel & 0xfffff); > +} > > Is this function operating directly on the instruction bundle in the > kernel code? If so, the bundle will contain some "interesting" > intermediate values as each of the "brl->xxx = yyy;" are processed. > If another cpu should try to execute this bundle while the modifications > are in progress, then the results will be not what you want. No, this function writes brl on kprobe's instruction buffer (kprobe.ainsn.insn->bundle[1]) when preparing the kprobe. So, other cpu never execute it, and we don't need to write it atomically. > On cpu models that support st16 you could construct the brl instruction > and use a single st16 to update the whole bundle atomically. > > -Tony Thank you again, -- Masami Hiramatsu Software Engineer Hitachi Computer Products (America) Inc. Software Solutions Division e-mail: mhiramat@xxxxxxxxxx - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
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