OK, I think I've got it - it certainly smells like a linkerism but I
didn't want to blame it until I actually found the bad code, but I
believe it's another instance of bug 745843 - a problem with the fixup
for the cortex-a8 branch erratum:
In the bad build we have:
00021fe0 <_GLOBAL__sub_I_netrc.cc>:
21fe0: b538 push {r3, r4, r5, lr}
21fe2: 4d08 ldr r5, [pc, #32] ; (22004
<_GLOBAL__sub_I_netrc.cc+0x24>)
21fe4: 4c08 ldr r4, [pc, #32] ; (22008
<_GLOBAL__sub_I_netrc.cc+0x28>)
21fe6: 447d add r5, pc
21fe8: 447c add r4, pc
21fea: 4628 mov r0, r5
21fec: f7ff e86c blx 210c8 <_init+0x290>
21ff0: 4b06 ldr r3, [pc, #24] ; (2200c
<_GLOBAL__sub_I_netrc.cc+0x2c>)
21ff2: 4628 mov r0, r5
21ff4: 58e1 ldr r1, [r4, r3]
21ff6: 4b06 ldr r3, [pc, #24] ; (22010
<_GLOBAL__sub_I_netrc.cc+0x30>)
21ff8: 58e2 ldr r2, [r4, r3]
21ffa: e8bd 4038 ldmia.w sp!, {r3, r4, r5, lr}
21ffe: f081 bfa3 b.w a3f48
Now that branch is on a word boundary which kicks the a8 erratum case,
so it has planted:
a3f48: f77d bc20 b.w 2178c <_init+0x954>
Now note we're in Thumb at the moment.
which unfortunately branches to the following ARM code in the PLT - it should
have branched a few bytes earlier, which is what Richard's fix in bug 745843
fixed.
2178c: e28fc600 add ip, pc, #0
21790: e28cca9f add ip, ip, #651264 ; 0x9f000
21794: e5bcfb84 ldr pc, [ip, #2948]! ; 0xb84
We reckoned that was a really unlikely bug to hit - maybe one in a few
thousand executables - trust it to land in apt!
Dave
** Also affects: binutils (Ubuntu)
Importance: Undecided
Status: New
** Changed in: gcc-linaro
Status: New => Invalid
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https://bugs.launchpad.net/bugs/774175
Title:
apt segfaults on armel in oneiric
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