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From: | Michael Matz |
Subject: | Re: [Tinycc-devel] x86_64 static link fix |
Date: | Sun, 13 Jan 2019 06:08:31 +0100 (CET) |
User-agent: | Alpine 2.21 (LSU 202 2017-01-01) |
Hi, On Wed, 9 Jan 2019, Kurt Nalty wrote:
After firing up gdb, and tracing through a few combinations of static and dynamically linked object files, I have determined that the segfaults were due to usage of procedure linking tables (.plt) with the statically linked process. The plt addresses are not corrected when static loaded, but are corrected during dynamic linking. File x86_64-gen.c, lines 630-634 were #ifdef TCC_TARGET_PE greloca(cur_text_section, vtop->sym, ind + 1, R_X86_64_PC32, (int)(vtop->c.i-4)); #else greloca(cur_text_section, vtop->sym, ind + 1, R_X86_64_PLT32, (int)(vtop->c.i-4)); #endif and are replaced by greloca(cur_text_section, vtop->sym, ind + 1, R_X86_64_PC32, (int)(vtop->c.i-4));This restores correct static linking in uClibc-0-9.30 and musl environments. Dynamic linking is unaffected, and continues to use procedure link table jumps and calls.
It's still wrong. The relocation to use really should be PLT32, even though it doesn't often make a difference (*).
I've now found time to look into this, i.e. static linking with uClibc. I fixed some problems in mob and reverted your patch again. A simple hello world now works statically with uClibc. Would be nice if you can retry (and maybe with bigger examples :) ).
Ciao, Michael.* it's a historic mistake of the initial x86-64 psABI implementations that PC32 relocs are sometimes used in place of PLT32 relocs (or from a different point of view, that both relocations exist, and not only PC32).
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