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[rfa] Detect __aeabi_read_tp even without symbols
- From: "Ulrich Weigand" <uweigand at de dot ibm dot com>
- To: gdb-patches at sourceware dot org, rearnsha at arm dot com
- Date: Wed, 20 Oct 2010 02:02:31 +0200 (CEST)
- Subject: [rfa] Detect __aeabi_read_tp even without symbols
even with the exception unwinder, there are still a couple of extra failures
on ARM when libc symbol information is missing.
One set of failures is related to the skip_prologue_function routine, which
is used to detect helper routines that are called *during* a function prologue,
so that the prologue parser should not stop when encountering a call to one
of these special routines (as opposed to regular function calls).
However, skip_prologue_function works by identifying the routine by *name*.
If no symbol information is present for libc, this may not work.
One case where this problem happens is in calls to __aeabi_read_tp early
in the prologue of certain glibc routines (like abort). This causes a
number of test case failures.
However, the __aeabi_read_tp implementation in glibc is actually easy to
recognize even in the absence of a function name: its *contents* are just
two ARM instructions, which are hard-coded as assembler in glibc and seem
unlikely to change (they just forward to the kernel-provided code in the
The following patch uses this idea to work around the issue. This fixes
these failures when running without libc symbol info:
FAIL: gdb.base/corefile.exp: print func2::coremaker_local
FAIL: gdb.base/corefile.exp: backtrace in corefile.exp
FAIL: gdb.base/relativedebug.exp: pause found in backtrace
Tested on armv7l-linux-gnueabi with no regressions.
OK for mainline?
* arm-tdep.c (thumb_analyze_prologue): Skip in-prologue calls to glibc
__aeabi_read_tp implementation even if no symbols are available.
RCS file: /cvs/src/src/gdb/arm-tdep.c,v
retrieving revision 1.310
diff -u -p -r1.310 arm-tdep.c
--- gdb/arm-tdep.c 12 Oct 2010 08:46:15 -0000 1.310
+++ gdb/arm-tdep.c 15 Oct 2010 14:11:40 -0000
@@ -822,7 +826,23 @@ thumb_analyze_prologue (struct gdbarch *
if (bit (inst2, 12) == 0)
nextpc = nextpc & 0xfffffffc;
- if (!skip_prologue_function (nextpc))
+ if (skip_prologue_function (nextpc))
+ /* If we run against a stripped glibc, skip_prologue_function
+ might not have been able to identify the special functions
+ by name. Check for one important case, __aeabi_read_tp,
+ by comparing the *code* against the default implementation
+ (this is hand-written ARM assembler in glibc, therefore we
+ need to check for BLX here). */
+ else if (bit (inst2, 12) == 0
+ && read_memory_unsigned_integer (nextpc, 4,
+ == 0xe3e00a0f /* mov r0, #0xffff0fff */
+ && read_memory_unsigned_integer (nextpc + 4, 4,
+ == 0xe240f01f) /* sub pc, r0, #31 */
Dr. Ulrich Weigand
GNU Toolchain for Linux on System z and Cell BE