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--enable-64-bit-bfd. Basically the issue happens when dealing with "bl" instructions: GDB does branch destination calculation and (wrongly) sign-extends the PC. Here is a piece of his original message explaining the problem: > next_pc = arm_get_next_pc (frame, get_frame_pc (frame)); > > /* The Linux kernel offers some user-mode helpers in a high page. We can > not read this page (as of 2.6.23), and even if we could then we couldn't > set breakpoints in it, and even if we could then the atomic operations > would fail when interrupted. They are all called as functions and return > to the address in LR, so step to there instead. */ > if (next_pc > 0xffff0000) > next_pc = get_frame_register_unsigned (frame, ARM_LR_REGNUM); > > arm_insert_single_step_breakpoint (gdbarch, aspace, next_pc); > > Unfortunately, branch destination addresses are SIGN EXTENDED to 64 > bits. So, > > (top-gdb) p/x next_pc > $14 = 0xffffffffb6df2864 > > Which triggers the next_pc = get_frame_register_unsigned(), and we > cannot step into any branches because the destination PC is wrong. Anyway, the fix is simple and Andrew himself provided it for us. It took a while for me to figure out how to trigger the bug (in order to write a testcase for it), but I finally made it. The attached patch fixes the problem (by casting to `unsigned long' instead of just `long'), and also includes a testcase to reproduce the issue. gdb/ChangeLog: 2013-04-22 Andrew Haley <aph@redhat.com> * arm-tdep.c (BranchDest): Cast result as "unsigned long", instead of "long". gdb/testsuite/ChangeLog: 2013-04-22 Sergio Durigan Junior <sergiodj@redhat.com> * gdb.arch/arm-bl-branch-dest.c: New file. * gdb.arch/arm-bl-branch-dest.exp: Likewise.
29 lines
847 B
C
29 lines
847 B
C
/* This testcase is part of GDB, the GNU debugger.
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Copyright 2013 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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static void
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foo (int a)
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{
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++a;
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}
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int
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main (int argc, char *argv[])
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{
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foo (10);
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return 0;
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}
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