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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.
262 lines
8.4 KiB
C
262 lines
8.4 KiB
C
/* Target-dependent code for GNU/Linux on Nios II.
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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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#include "defs.h"
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#include "frame.h"
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#include "osabi.h"
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#include "solib-svr4.h"
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#include "trad-frame.h"
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#include "tramp-frame.h"
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#include "symtab.h"
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#include "regset.h"
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#include "regcache.h"
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#include "linux-tdep.h"
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#include "glibc-tdep.h"
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#include "nios2-tdep.h"
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/* Core file and register set support. */
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/* Map from the normal register enumeration order to the order that
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registers appear in core files, which corresponds to the order
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of the register slots in the kernel's struct pt_regs. */
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static const int reg_offsets[NIOS2_NUM_REGS] =
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{
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-1, 8, 9, 10, 11, 12, 13, 14, /* r0 - r7 */
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0, 1, 2, 3, 4, 5, 6, 7, /* r8 - r15 */
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23, 24, 25, 26, 27, 28, 29, 30, /* r16 - r23 */
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-1, -1, 19, 18, 17, 21, -1, 16, /* et bt gp sp fp ea sstatus ra */
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21, /* pc */
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-1, 20, -1, -1, -1, -1, -1, -1, /* status estatus ... */
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-1, -1, -1, -1, -1, -1, -1, -1
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};
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/* General register set size. Should match sizeof (struct pt_regs) +
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sizeof (struct switch_stack) from the NIOS2 Linux kernel patch. */
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#define NIOS2_GREGS_SIZE (4 * 34)
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/* Implement the supply_regset hook for core files. */
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static void
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nios2_supply_gregset (const struct regset *regset,
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struct regcache *regcache,
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int regnum, const void *gregs_buf, size_t len)
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{
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const gdb_byte *gregs = (const gdb_byte *) gregs_buf;
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int regno;
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static const gdb_byte zero_buf[4] = {0, 0, 0, 0};
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for (regno = NIOS2_Z_REGNUM; regno <= NIOS2_MPUACC_REGNUM; regno++)
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if (regnum == -1 || regnum == regno)
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{
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if (reg_offsets[regno] != -1)
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regcache->raw_supply (regno, gregs + 4 * reg_offsets[regno]);
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else
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regcache->raw_supply (regno, zero_buf);
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}
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}
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/* Implement the collect_regset hook for core files. */
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static void
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nios2_collect_gregset (const struct regset *regset,
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const struct regcache *regcache,
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int regnum, void *gregs_buf, size_t len)
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{
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gdb_byte *gregs = (gdb_byte *) gregs_buf;
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int regno;
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for (regno = NIOS2_Z_REGNUM; regno <= NIOS2_MPUACC_REGNUM; regno++)
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if (regnum == -1 || regnum == regno)
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{
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if (reg_offsets[regno] != -1)
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regcache->raw_collect (regno, gregs + 4 * reg_offsets[regno]);
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}
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}
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static const struct regset nios2_core_regset =
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{
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NULL,
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nios2_supply_gregset,
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nios2_collect_gregset
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};
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/* Iterate over core file register note sections. */
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static void
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nios2_iterate_over_regset_sections (struct gdbarch *gdbarch,
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iterate_over_regset_sections_cb *cb,
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void *cb_data,
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const struct regcache *regcache)
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{
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cb (".reg", NIOS2_GREGS_SIZE, NIOS2_GREGS_SIZE, &nios2_core_regset, NULL,
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cb_data);
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}
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/* Initialize a trad-frame cache corresponding to the tramp-frame.
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FUNC is the address of the instruction TRAMP[0] in memory.
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This ABI is not documented. It corresponds to rt_setup_ucontext in
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the kernel arch/nios2/kernel/signal.c file.
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The key points are:
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- The kernel creates a trampoline at the hard-wired address 0x1044.
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- The stack pointer points to an object of type struct rt_sigframe.
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The definition of this structure is not exported from the kernel.
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The register save area is located at offset 152 bytes (as determined
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by inspection of the stack contents in the debugger), and the
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registers are saved as r1-r23, ra, fp, gp, ea, sp.
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This interface was implemented with kernel version 3.19 (the first
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official mainline kernel). Older unofficial kernel versions used
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incompatible conventions; we do not support those here. */
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#define NIOS2_SIGRETURN_TRAMP_ADDR 0x1044
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#define NIOS2_SIGRETURN_REGSAVE_OFFSET 152
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static void
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nios2_linux_rt_sigreturn_init (const struct tramp_frame *self,
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struct frame_info *next_frame,
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struct trad_frame_cache *this_cache,
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CORE_ADDR func)
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{
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CORE_ADDR sp = get_frame_register_unsigned (next_frame, NIOS2_SP_REGNUM);
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CORE_ADDR base = sp + NIOS2_SIGRETURN_REGSAVE_OFFSET;
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int i;
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for (i = 0; i < 23; i++)
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trad_frame_set_reg_addr (this_cache, i + 1, base + i * 4);
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trad_frame_set_reg_addr (this_cache, NIOS2_RA_REGNUM, base + 23 * 4);
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trad_frame_set_reg_addr (this_cache, NIOS2_FP_REGNUM, base + 24 * 4);
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trad_frame_set_reg_addr (this_cache, NIOS2_GP_REGNUM, base + 25 * 4);
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trad_frame_set_reg_addr (this_cache, NIOS2_PC_REGNUM, base + 27 * 4);
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trad_frame_set_reg_addr (this_cache, NIOS2_SP_REGNUM, base + 28 * 4);
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/* Save a frame ID. */
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trad_frame_set_id (this_cache, frame_id_build (base, func));
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}
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/* Trampoline for sigreturn. This has the form
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movi r2, __NR_rt_sigreturn
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trap 0
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appropriately encoded for R1 or R2. */
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static struct tramp_frame nios2_r1_linux_rt_sigreturn_tramp_frame =
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{
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SIGTRAMP_FRAME,
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4,
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{
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{ MATCH_R1_MOVI | SET_IW_I_B (2) | SET_IW_I_IMM16 (139), ULONGEST_MAX },
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{ MATCH_R1_TRAP | SET_IW_R_IMM5 (0), ULONGEST_MAX},
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{ TRAMP_SENTINEL_INSN }
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},
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nios2_linux_rt_sigreturn_init
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};
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static struct tramp_frame nios2_r2_linux_rt_sigreturn_tramp_frame =
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{
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SIGTRAMP_FRAME,
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4,
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{
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{ MATCH_R2_MOVI | SET_IW_F2I16_B (2) | SET_IW_F2I16_IMM16 (139), ULONGEST_MAX },
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{ MATCH_R2_TRAP | SET_IW_X2L5_IMM5 (0), ULONGEST_MAX},
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{ TRAMP_SENTINEL_INSN }
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},
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nios2_linux_rt_sigreturn_init
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};
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/* When FRAME is at a syscall instruction, return the PC of the next
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instruction to be executed. */
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static CORE_ADDR
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nios2_linux_syscall_next_pc (struct frame_info *frame,
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const struct nios2_opcode *op)
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{
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CORE_ADDR pc = get_frame_pc (frame);
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ULONGEST syscall_nr = get_frame_register_unsigned (frame, NIOS2_R2_REGNUM);
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/* If we are about to make a sigreturn syscall, use the unwinder to
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decode the signal frame. */
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if (syscall_nr == 139 /* rt_sigreturn */)
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return frame_unwind_caller_pc (frame);
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return pc + op->size;
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}
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/* Return true if PC is a kernel helper, a function mapped by the kernel
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into user space on an unwritable page. Currently the only such function
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is __kuser_cmpxchg at 0x1004. See arch/nios2/kernel/entry.S in the Linux
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kernel sources and sysdeps/unix/sysv/linux/nios2/atomic-machine.h in
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GLIBC. */
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static bool
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nios2_linux_is_kernel_helper (CORE_ADDR pc)
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{
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return pc == 0x1004;
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}
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/* Hook function for gdbarch_register_osabi. */
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static void
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nios2_linux_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
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{
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struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
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linux_init_abi (info, gdbarch);
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/* Shared library handling. */
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set_gdbarch_skip_trampoline_code (gdbarch, find_solib_trampoline_target);
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set_gdbarch_skip_solib_resolver (gdbarch, glibc_skip_solib_resolver);
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set_solib_svr4_fetch_link_map_offsets (gdbarch,
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svr4_ilp32_fetch_link_map_offsets);
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/* Enable TLS support. */
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set_gdbarch_fetch_tls_load_module_address (gdbarch,
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svr4_fetch_objfile_link_map);
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/* Core file support. */
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set_gdbarch_iterate_over_regset_sections
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(gdbarch, nios2_iterate_over_regset_sections);
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/* Linux signal frame unwinders. */
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if (gdbarch_bfd_arch_info (gdbarch)->mach == bfd_mach_nios2r2)
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tramp_frame_prepend_unwinder (gdbarch,
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&nios2_r2_linux_rt_sigreturn_tramp_frame);
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else
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tramp_frame_prepend_unwinder (gdbarch,
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&nios2_r1_linux_rt_sigreturn_tramp_frame);
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tdep->syscall_next_pc = nios2_linux_syscall_next_pc;
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tdep->is_kernel_helper = nios2_linux_is_kernel_helper;
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/* Index of target address word in glibc jmp_buf. */
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tdep->jb_pc = 10;
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}
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void
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_initialize_nios2_linux_tdep (void)
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{
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const struct bfd_arch_info *arch_info;
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for (arch_info = bfd_lookup_arch (bfd_arch_nios2, 0);
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arch_info != NULL;
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arch_info = arch_info->next)
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gdbarch_register_osabi (bfd_arch_nios2, arch_info->mach,
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GDB_OSABI_LINUX, nios2_linux_init_abi);
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}
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