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[Bug external/8841] Can not set breakpoints in the vsyscall page


http://sourceware.org/bugzilla/show_bug.cgi?id=8841

--- Comment #3 from chn <kalvdans at gmail dot com> 2012-03-04 20:08:53 UTC ---
It does not work on my Fedora 16 system, Linux 3.2:

chn@jaz:~$ uname -r
3.2.7-1.fc16.x86_64
chn@jaz:~$ gdb /bin/ls
GNU gdb (GDB) Fedora (7.3.50.20110722-10.fc16)
Copyright (C) 2011 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-redhat-linux-gnu".
For bug reporting instructions, please see:
<http://www.gnu.org/software/gdb/bugs/>...
Reading symbols from /bin/ls...(no debugging symbols found)...done.
Missing separate debuginfos, use: debuginfo-install
coreutils-8.12-6.fc16.x86_64
(gdb) break *0xffffffffff600000
Breakpoint 1 at 0xffffffffff600000
(gdb) r
Starting program: /bin/ls 
Warning:
Cannot insert breakpoint 1.
Error accessing memory address 0xffffffffff600000: Input/output error.
(gdb) 

Strace of gdb shows that it fails to insert the 0xcc int3 opcode on the
vsyscall page:

ptrace(PTRACE_GETREGS, 26776, 0, 0x7fff9d80cdf0) = 0
ptrace(PTRACE_SETREGS, 26776, 0, 0x7fff9d80cdf0) = 0
ptrace(PTRACE_PEEKTEXT, 26776, 0x3f65e0f990, [0x2e6666666666c3f3]) = 0
ptrace(PTRACE_PEEKTEXT, 26776, 0x3f65e0f990, [0x2e6666666666c3f3]) = 0
ptrace(PTRACE_POKEDATA, 26776, 0x3f65e0f990, 0x2e6666666666c3cc) = 0
ptrace(PTRACE_PEEKTEXT, 26776, 0xffffffffff600000, [0xf00000060c0c748]) = 0
ptrace(PTRACE_PEEKTEXT, 26776, 0xffffffffff600000, [0xf00000060c0c748]) = 0
ptrace(PTRACE_POKEDATA, 26776, 0xffffffffff600000, 0xf00000060c0c7cc) = -1 EIO
(Input/output error)
ptrace(PTRACE_POKETEXT, 26776, 0xffffffffff600000, 0xf00000060c0c7cc) = -1 EIO
(Input/output error)

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