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[ob] Fix sizeof buffer used by ptrace(tls)
- From: Andrew Cagney <ac131313 at redhat dot com>
- To: gdb-patches at sources dot redhat dot com
- Date: Tue, 26 Aug 2003 15:37:39 -0400
- Subject: [ob] Fix sizeof buffer used by ptrace(tls)
Hello,
The buffer returned by PTRACE_GET_THREAD_AREA is 4x4 bytes not 3x4
bytes. This fixes the size and adds a few more comments about what is
happening.
committed to mainline and 6.0 branch,
Andrew
2003-08-26 Andrew Cagney <cagney@redhat.com>
* i386-linux-nat.c (ps_get_thread_area): Make "desc" four "int"s
in size. Add comments.
Index: i386-linux-nat.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-linux-nat.c,v
retrieving revision 1.49
diff -u -r1.49 i386-linux-nat.c
--- i386-linux-nat.c 23 Aug 2003 08:56:45 -0000 1.49
+++ i386-linux-nat.c 26 Aug 2003 19:33:12 -0000
@@ -687,11 +687,31 @@
perror_with_name ("Couldn't write debug register");
}
+/* Called by libthread_db. Return's a pointer to the thread local
+ storage (or it's descriptor). */
extern ps_err_e
ps_get_thread_area(const struct ps_prochandle *ph,
lwpid_t lwpid, int idx, void **base)
{
- unsigned long int desc[3];
+ /* NOTE: cagney/2003-08-26: The definition of this buffer is found
+ in the kernel header <asm-i386/ldt.h>. It, after padding, is 4 x
+ 4 byte integers in size: "entry_number", "base_addr", "limit",
+ and a bunch of status bits.
+
+ The values returned by this ptrace call should be part of the
+ regcache buffer, and ps_get_thread_area should channel its
+ request through the regcache. That way remote targets could
+ provide the value using the remote protocol and not this direct
+ call.
+
+ Is this function needed? I'm guessing that the "base" is the
+ address of a a descriptor that libthread_db uses to find the
+ thread local address base that GDB needs. Perhaphs that
+ descriptor is defined by the ABI. Anyway, given that
+ libthread_db calls this function without prompting (gdb
+ requesting tls base) I guess it needs info in there anyway. */
+ unsigned int desc[4];
+ gdb_assert (sizeof (int) == 4);
#define PTRACE_GET_THREAD_AREA 25
if (ptrace (PTRACE_GET_THREAD_AREA,