Re: dash behaviour, was Re: core dump analysis
Finn Thain <[email protected]>
| Newsgroups | gmane.linux.ports.m68k,gmane.linux.debian.ports.68k |
|---|---|
| Message-ID | <[email protected]> |
On Sun, 9 Apr 2023, Michael Schmitz wrote: > > > > The only way I have found to alter dash's inclination to crash is to > > reboot. (I said previously I was unable to reproduce this in a single > > user mode shell but it turned out to be more subtle.) > > I wonder what could change from one boot to another - can you have dash > (and its subshells) dump /proc/self/maps and see whether there's any > variation in that? But what we really need is the physical mappings. How > can we find those? > > With the kernel RNG disabled, I would expect neither of these mappings > to change between boots? > It looks like the stack area still changes across invocations: # sh # cat < /proc/self/maps c0000000-c0021000 r-xp 00000000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c0021000-c0023000 rw-p 00000000 00:00 0 c0023000-c0024000 r--p 00021000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c0024000-c0026000 rw-p 00022000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c002a000-c0199000 r-xp 00000000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c0199000-c019a000 ---p 0016f000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c019a000-c019c000 r--p 00170000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c019c000-c01a0000 rw-p 00172000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c01a0000-c01aa000 rw-p 00000000 00:00 0 d0000000-d0019000 r-xp 00000000 08:06 32713 /usr/bin/dash d001b000-d001c000 r--p 00019000 08:06 32713 /usr/bin/dash d001c000-d001d000 rw-p 0001a000 08:06 32713 /usr/bin/dash d001d000-d001f000 rwxp 00000000 00:00 0 [heap] d001f000-d0040000 rwxp 00000000 00:00 0 [heap] eff9f000-effc0000 rw-p 00000000 00:00 0 [stack] # sh # cat < /proc/self/maps c0000000-c0021000 r-xp 00000000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c0021000-c0023000 rw-p 00000000 00:00 0 c0023000-c0024000 r--p 00021000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c0024000-c0026000 rw-p 00022000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c002a000-c0199000 r-xp 00000000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c0199000-c019a000 ---p 0016f000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c019a000-c019c000 r--p 00170000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c019c000-c01a0000 rw-p 00172000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c01a0000-c01aa000 rw-p 00000000 00:00 0 d0000000-d0019000 r-xp 00000000 08:06 32713 /usr/bin/dash d001b000-d001c000 r--p 00019000 08:06 32713 /usr/bin/dash d001c000-d001d000 rw-p 0001a000 08:06 32713 /usr/bin/dash d001d000-d001f000 rwxp 00000000 00:00 0 [heap] d001f000-d0040000 rwxp 00000000 00:00 0 [heap] effd8000-efff9000 rw-p 00000000 00:00 0 [stack] # sh # cat < /proc/self/maps c0000000-c0021000 r-xp 00000000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c0021000-c0023000 rw-p 00000000 00:00 0 c0023000-c0024000 r--p 00021000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c0024000-c0026000 rw-p 00022000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c002a000-c0199000 r-xp 00000000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c0199000-c019a000 ---p 0016f000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c019a000-c019c000 r--p 00170000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c019c000-c01a0000 rw-p 00172000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c01a0000-c01aa000 rw-p 00000000 00:00 0 d0000000-d0019000 r-xp 00000000 08:06 32713 /usr/bin/dash d001b000-d001c000 r--p 00019000 08:06 32713 /usr/bin/dash d001c000-d001d000 rw-p 0001a000 08:06 32713 /usr/bin/dash d001d000-d001f000 rwxp 00000000 00:00 0 [heap] d001f000-d0040000 rwxp 00000000 00:00 0 [heap] effdf000-f0000000 rw-p 00000000 00:00 0 [stack] # That can be disabled easily though (see below). I'll have to modify some init scripts to find out what effect it has. # setarch -R sh # sh # cat < /proc/self/maps c0000000-c0021000 r-xp 00000000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c0021000-c0023000 rw-p 00000000 00:00 0 c0023000-c0024000 r--p 00021000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c0024000-c0026000 rw-p 00022000 08:06 38780 /usr/lib/m68k-linux-gnu/ld.so.1 c002a000-c0199000 r-xp 00000000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c0199000-c019a000 ---p 0016f000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c019a000-c019c000 r--p 00170000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c019c000-c01a0000 rw-p 00172000 08:06 38786 /usr/lib/m68k-linux-gnu/libc.so.6 c01a0000-c01aa000 rw-p 00000000 00:00 0 d0000000-d0019000 r-xp 00000000 08:06 32713 /usr/bin/dash d001b000-d001c000 r--p 00019000 08:06 32713 /usr/bin/dash d001c000-d001d000 rw-p 0001a000 08:06 32713 /usr/bin/dash d001d000-d001f000 rwxp 00000000 00:00 0 [heap] d001f000-d0040000 rwxp 00000000 00:00 0 [heap] effdf000-f0000000 rw-p 00000000 00:00 0 [stack] # md5sum < /proc/self/maps baacbaf944fb01d3200d924da7f7a815 - # sh # md5sum < /proc/self/maps baacbaf944fb01d3200d924da7f7a815 - # sh # md5sum < /proc/self/maps baacbaf944fb01d3200d924da7f7a815 -