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Re: [PATCH] thumb fixes
On Thu, 2008-09-04 at 15:25 +0300, Mikko Rapeli wrote:
> I suppose 0x8928 is in plt ELF section where objdump also shows a few
> undefined instrunctions:
They aren't instructions, they're data entries The PLT sequence loads
that value and jumps to it. Note that PLT sequences rely on the target
being either an ARM instruction or that the CPU running the code is v5t
or later (since ldr pc does not interwork correctly on v4t).
> 00008908 <.plt>:
> 8908: e52de004 str lr, [sp, #-4]!
> 890c: e59fe004 ldr lr, [pc, #4] ; 8918 <.plt+0x10>
> 8910: e08fe00e add lr, pc, lr
> 8914: e5bef008 ldr pc, [lr, #8]!
> 8918: 0000922c andeq r9, r0, ip, lsr #4
> 891c: e28fc600 add ip, pc, #0 ; 0x0
> 8920: e28cca09 add ip, ip, #36864 ; 0x9000
> 8924: e5bcf22c ldr pc, [ip, #556]!
> 8928: 46c04778 undefined
> 892c: e28fc600 add ip, pc, #0 ; 0x0
> 8930: e28cca09 add ip, ip, #36864 ; 0x9000
> 8934: e5bcf220 ldr pc, [ip, #544]!
> 8938: 46c04778 undefined
> 893c: e28fc600 add ip, pc, #0 ; 0x0
> 8940: e28cca09 add ip, ip, #36864 ; 0x9000
> 8944: e5bcf214 ldr pc, [ip, #532]!
> 8948: 46c04778 undefined
> I don't know what this .plt section is or which object files it's coming
> from, but I suspect the dynamic linker ld.elf_so. Hopefully compiling it
> in ARM mode would solve this. But at least a dynamic /bin/echo works in
> thumb mode now :)
PLT sequences are used for inter-library calls and are intended to
support dynamic loading and lazy binding (resolving the symbol only when
Before you start messing with that, you should probably read the ARM
Procedure call documentation carefully (see
Although NetBSD doesn't conform to the latest version of the spec many of the
notes will be useful.
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