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f489207efd
This patch fixes a problem on nios2-linux-gnu with stepping past the
kernel helper __kuser_cmpxchg, which was exposed by the testcase
gdb.threads/watchpoint-fork.exp. The kernel maps this function into
user space on an unwritable page. In this testcase, the cmpxchg
helper is invoked indirectly from the setbuf call in the test program.
Since this target lacks hardware breakpoint/watchpoint support, GDB
tries to single-step through the program by setting software
breakpoints, and was just giving an error when it reached the function
on the unwritable page.
The solution here is to always step over the call instead of stepping
into it; cmpxchg is supposed to be an atomic operation so this
behavior seems reasonable. The hook in nios2_get_next_pc is somewhat
generic, but at present cmpxchg is the only helper provided by the
Linux kernel that is invoked by an ordinary function call. (Signal
return trampolines also go through the unwritable page but not by a
function call.)
Fixing this issue also revealed that the testcase needs a much larger
timeout factor when software single-stepping is used. That has also
been fixed in this patch.
gdb/ChangeLog
2019-03-28 Sandra Loosemore <sandra@codesourcery.com>
* nios2-tdep.h (struct gdbarch_tdep): Add is_kernel_helper.
* nios2-tdep.c (nios2_get_next_pc): Skip over kernel helpers.
* nios2-linux-tdep.c (nios2_linux_is_kernel_helper): New.
(nios2_linux_init_abi): Install it.
gdb/testsuite/ChangeLog
2019-03-28 Sandra Loosemore <sandra@codesourcery.com>
* gdb.threads/watchpoint-fork.exp (test): Use large timeout
factor when no hardware watchpoint support.
89 lines
2.9 KiB
C
89 lines
2.9 KiB
C
/* Target-dependent header for the Nios II architecture, for GDB.
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Copyright (C) 2012-2019 Free Software Foundation, Inc.
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Contributed by Mentor Graphics, Inc.
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This file is part of GDB.
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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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#ifndef NIOS2_TDEP_H
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#define NIOS2_TDEP_H
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/* Nios II ISA specific encodings and macros. */
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#include "opcode/nios2.h"
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/* Registers. */
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#define NIOS2_Z_REGNUM 0 /* Zero */
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#define NIOS2_R2_REGNUM 2 /* used for return value */
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#define NIOS2_R3_REGNUM 3 /* used for return value */
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/* Used for hidden zero argument to store ptr to struct return value. */
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#define NIOS2_R4_REGNUM 4
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#define NIOS2_R7_REGNUM 7
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#define NIOS2_GP_REGNUM 26 /* Global Pointer */
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#define NIOS2_SP_REGNUM 27 /* Stack Pointer */
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#define NIOS2_FP_REGNUM 28 /* Frame Pointer */
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#define NIOS2_EA_REGNUM 29 /* Exception address */
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#define NIOS2_BA_REGNUM 30 /* Breakpoint return address */
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#define NIOS2_RA_REGNUM 31 /* Return address */
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#define NIOS2_PC_REGNUM 32
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/* Control registers. */
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#define NIOS2_STATUS_REGNUM 33
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#define NIOS2_ESTATUS_REGNUM 34
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#define NIOS2_BSTATUS_REGNUM 35
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#define NIOS2_IENABLE_REGNUM 36
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#define NIOS2_IPENDING_REGNUM 37
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#define NIOS2_CPUID_REGNUM 38
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#define NIOS2_EXCEPTION_REGNUM 40
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#define NIOS2_PTEADDR_REGNUM 41
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#define NIOS2_TLBACC_REGNUM 42
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#define NIOS2_TLBMISC_REGNUM 43
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#define NIOS2_ECCINJ_REGNUM 44
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#define NIOS2_BADADDR_REGNUM 45
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#define NIOS2_CONFIG_REGNUM 46
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#define NIOS2_MPUBASE_REGNUM 47
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#define NIOS2_MPUACC_REGNUM 48
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/* R4-R7 are used for argument passing. */
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#define NIOS2_FIRST_ARGREG NIOS2_R4_REGNUM
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#define NIOS2_LAST_ARGREG NIOS2_R7_REGNUM
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/* Number of all registers. */
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#define NIOS2_NUM_REGS 49
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/* Size of an instruction, in bytes. */
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#define NIOS2_OPCODE_SIZE 4
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#define NIOS2_CDX_OPCODE_SIZE 2
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/* Target-dependent structure in gdbarch. */
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struct gdbarch_tdep
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{
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/* Assumes FRAME is stopped at a syscall (trap) instruction; returns
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the expected next PC. */
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CORE_ADDR (*syscall_next_pc) (struct frame_info *frame,
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const struct nios2_opcode *op);
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/* Returns true if PC points to a kernel helper function. */
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bool (*is_kernel_helper) (CORE_ADDR pc);
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/* Offset to PC value in jump buffer.
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If this is negative, longjmp support will be disabled. */
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int jb_pc;
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};
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extern struct target_desc *tdesc_nios2_linux;
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extern struct target_desc *tdesc_nios2;
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#endif /* NIOS2_TDEP_H */
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