Date: Mon, 22 Feb 1999 19:40:02 -0800 (PST) From: John Polstra <jdp@polstra.com> To: Archie Cobbs <archie@whistle.com> Cc: hackers@FreeBSD.ORG, (Terry Lambert) <terry@whistle.com> Subject: Re: Interesting ld.so bug Message-ID: <XFMail.990222194002.jdp@polstra.com> In-Reply-To: <199902221912.LAA76945@bubba.whistle.com>
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Archie Cobbs wrote:
> Terry Lambert writes:
>> There appears to be a bug with ld.so. The following steps illustrate
>> the bug:
>
> After some further playing around, it seems like it may be a linker
> problem, or a least a problem in the way we're using it.
>
> Here's my test case that reproduces the problem:
>
> We compile a shared library "libfoo" containing these source files:
>
> bar.c - Containing functions bar1() and bar2(), which are
> both exported. Function bar1() calls function bar2().
>
> java_jni.c - Java JNI method to interface to function bar1(),
> call it Java_bar1().
>
> db.c - Other exported routines. The C code in this file
> uses GDBM routines. NOTE: GDBM routines live in
> a static library, /usr/local/lib/libgdbm.a.
>
> Now when we run a java class that uses the java_jni.c native method,
> the call to Java_bar1() succeeds, and the call from there to bar1()
> succeeds, but when bar1() tries to call bar2(), it jumps to a very
> low address and segfaults. It seems that the bar2() trampoline is
> using an uninitialized base address or whatever.
>
> NOW, if we remove "db.c" from the compilation of "libfoo.so",
> then everything works!
Was the code in the static libgdbm.a library compiled with -fpic?
I bet it wasn't, and that's probably the problem. All code that's
included in a shared library should be PIC code.
John
---
John Polstra jdp@polstra.com
John D. Polstra & Co., Inc. Seattle, Washington USA
"Nobody ever went broke underestimating the taste of the American public."
-- H. L. Mencken
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