[Bug 49139] Regression: Wine crashes on startup on FreeBSD >= 5.7

[WineHQ Bugzilla]

https://bugs.winehq.org/show_bug.cgi?id=49139

--- Comment #5 from Damjan Jovanovic <damjan.jov at gmail.com> ---
Gen, thank you so much for your debugging so far. It would have taken me
forever to get started without it. I've begun my own debugging from the other
end: how the bad value gets into the binary in the first place.

Your patch modifies dlls/ntdll/loader.c to use dyn->d_un.d_ptr as the
initializer address instead of map->l_addr + dyn->d_un.d_val when its d_tag is
0x60009992. The d_tag of 0x60009992 comes from winebuild, function
fixup_elf32(), called from fixup_constructors(), called from main() when
"--fixup-ctors" was passed as a command line option. winebuild gets passed
--fixup-ctors from winegcc when its own function fixup_constuctors() is called,
and the commit I bisected the regression to
(1ccd638b1aa85fb3c43b49d69d279cd509ebdc21) calls fixup_constructors() in a new
place.

However what does 0x60009992 actually do? The fixup_elf32() function in
winebuild iterates over (what are effectively) Elf32_Dyn entries in the
PT_DYNAMIC section, and overwrites the d_tag containing DT_INIT with
0x60009992. Presumably, this is done so ELF initializers aren't run in the
native dynamic loader, but in Wine's NTDLL. But the 0x60009992 is still in
every other way a DT_INIT entry.

Testing on native FreeBSD binaries on both i386 and amd64 shows how (1) the
DT_INIT value in my own test executable on disk matches the value returned by
dlinfo() in memory, and (2) the value is also given by "objdump -x
<executable>|grep INIT".

But is that value an absolute address, or an offset relative to l_addr? Both
Wine and glibc seem to treat it as the latter:
https://code.woboq.org/userspace/glibc/elf/dl-init.c.html#58
    DL_CALL_DT_INIT(l, l->l_addr + l->l_info[DT_INIT]->d_un.d_ptr, argc, argv,
env);

-- 
Do not reply to this email, post in Bugzilla using the
above URL to reply.
You are receiving this mail because:
You are watching all bug changes.