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POAIX loadquery() return value interpretation (was also SEGV in 64-bit mode)
 

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    <p>I'm trying to compile Ruby 1.9.3-p125 on AIX 5.3 using xlc_r. I want to use the --enable-load-relative but that's dependent on the dladdr() function to get the pathname of the Ruby shared library and dladdr() isn't available on AIX. I found an implementation of dladdr() <a href="http://root.cern.ch/drupal/content/aix-and-dladdr" rel="nofollow">here on root.cern.ch</a> for AIX based on a call to loadquery(L_GETINFO).</p> <p>The loadquery(L_GETINFO) call gets a list of the binary files that make up a program. So to implement dladdr(), I'm doing a check to see if the address of the function passed to dladdr is between ldinfo_textorg and ldinfo_textorg+ldinfo_textsize. But the address of the function isn't within this address range for <em>any</em> of the structures returned. Maybe I'm not correctly interpreting the ld_info structure.</p> <p>I've attached the code I'm testing. Any help that can be rendered to these questions will be much appreciated.</p> <pre><code>#include &lt;sys/types.h&gt; #include &lt;sys/ldr.h&gt; #include &lt;stdlib.h&gt; #include &lt;stdio.h&gt; typedef struct { char* dli_fname; } Dl_info; int dladdr(void* s, Dl_info* i) { size_t bufSize = 40960; struct ld_info* ldi; void *buf; int r; printf("sym at %lu\n", (ulong)s); buf = (void *)malloc(bufSize); if (!buf) { i-&gt;dli_fname = 0; return 0; } r = loadquery((int)L_GETINFO, buf, (int)bufSize); if (r == -1) { i-&gt;dli_fname = 0; return 0; } do { ldi = (struct ld_info*)buf; printf("checking %s, text %lu - %lu\n", ldi-&gt;ldinfo_filename, (ulong)ldi-&gt;ldinfo_textorg, (ulong)(ldi-&gt;ldinfo_textorg + ldi-&gt;ldinfo_textsize)); if ((ldi-&gt;ldinfo_textorg &lt;= s) &amp;&amp; (s &lt; (ldi-&gt;ldinfo_textorg + ldi-&gt;ldinfo_textsize))) { i-&gt;dli_fname = ldi-&gt;ldinfo_filename; return 1; } buf += ldi-&gt;ldinfo_next; } while (ldi-&gt;ldinfo_next); i-&gt;dli_fname = 0; return 0; } int test_func() { 1; } int main() { Dl_info dli; int rc = dladdr((void *)test_func, &amp;dli); printf("rc = %d\n", rc); if (rc) { printf("dli.dli_fname = %s\n", dli.dli_fname); } } </code></pre> <p><strong>Update 30-Apr-2012:</strong> When I originally posted this question, I was also seeing loadquery(L_GETINFO) cause a segmentation violation when called from a 64-bit program. I can't live without 64-bit so this was a showstopper for me. This now looks like it's a problem with the installation of the compiler; other AIX machines can compile and run the code in 64-bit mode.</p> <p>The stack back-trace looked like this:</p> <pre><code>.() at 0xf458 usl_getinfo_user(??, ??, ??, ??) at 0x9fffffff00096b8 uloadquery(??, ??, ??, ??, ??, ??, ??) at 0x9fffffff0009b40 loadquery(0x200000002, 0x1000b3f0, 0xa0000000a000, 0x0, 0x0, 0x0, 0x0, 0x0) at 0x900000000043874 dladdr(s = 0x0000000110000900, i = 0x0ffffffffffffa00), line 18 in "dladdr.c" main(), line 11 in "test_dladdr.c" </code></pre>
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    1. COnote the relatively small number of followers each of your tags has (roll-over with mouse to see). As this is c code, you'll get a lot more eye-balls on your problem if you include a tag for 'c' (don't know if it called 'c' or 'c-lang' or ?? Good luck.
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    2. CO@shellter, yes you're right and I think it's 'c'. I woke up this morning thinking exactly this. Thanks!
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