toolchain/46476: on i386, gdb silently fails to set a breakpoint on PaX-MPROTECTed binary

[dyoung%ojctech.com@localhost]

>Number:         46476
>Category:       toolchain
>Synopsis:       on i386, gdb silently fails to set a breakpoint on 
>PaX-MPROTECTed binary
>Confidential:   no
>Severity:       serious
>Priority:       low
>Responsible:    toolchain-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed May 23 16:45:00 +0000 2012
>Originator:     David Young
>Release:        NetBSD 5.1rc4
>Organization:
>Environment:
>Description:
        When I try to set a breakpoint in a program that's protected
        with 'paxctl +M', the breakpoint isn't actually activated
        because of the MPROTECTion, but gdb does not tell me so
        because of some deficiency in gdb's error checking.

        gdb needs to check for and report the failure.

>How-To-Repeat:
        % paxctl +M program
        % gdb program
        (gdb) break main
        (gdb) run
        *never breaks*
>Fix:
        Improve error checking, but how?