Messages in this thread | | | Date | Mon, 12 Feb 2018 16:19:35 +0100 | From | Oleg Nesterov <> | Subject | Re: Uprobe: Bug(?) when probing small binaries |
| |
Hi Ravi,
On 02/12, Ravi Bangoria wrote: > > I'm observing a bug in the uprobe infrastructure.
I am not sure,
> When target binary > is quite small, uprobe replaces 'trap' instruction at two different > places. Ex,
but this is actually "the same place" (in the file), just 2 virtual addrs differ,
> (gdb) x/w 0x1001069c > 0x1001069c: 2080899750 > > Now enable the probe: > > # echo 1 > events/probe_a/main/enable > > Check probed instruction: > > (gdb) disassemble main > 0x000000001000069c <+8>: trap > > *Bug*: > > (gdb) x/w 0x1001069c > 0x1001069c: 2145386504 > > In short, when it replaces the probe instruction, it does some corruption > in the readonly vma. This seems to be a bug. > > How did I get the other address 0x1001069c?I found build_map_info() > returns these two vmas for the single probe: > > 10000000-10010000 r-xp 00000000 08:05 67325595 /home/ravi/a.out > 10010000-10020000 r--p 00000000 08:05 67325595 /home/ravi/a.out
please note that these 2 vma's mmap the same region in a.out, so *0x1001069c and *0x1000069c point to the same insn.
Oleg.
| |