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c1fe190c06
This adds a flag so that the DAWR can be enabled on P9 via:
echo Y > /sys/kernel/debug/powerpc/dawr_enable_dangerous
The DAWR was previously force disabled on POWER9 in:
9654153158 powerpc: Disable DAWR in the base POWER9 CPU features
Also see Documentation/powerpc/DAWR-POWER9.txt
This is a dangerous setting, USE AT YOUR OWN RISK.
Some users may not care about a bad user crashing their box
(ie. single user/desktop systems) and really want the DAWR. This
allows them to force enable DAWR.
This flag can also be used to disable DAWR access. Once this is
cleared, all DAWR access should be cleared immediately and your
machine once again safe from crashing.
Userspace may get confused by toggling this. If DAWR is force
enabled/disabled between getting the number of breakpoints (via
PTRACE_GETHWDBGINFO) and setting the breakpoint, userspace will get an
inconsistent view of what's available. Similarly for guests.
For the DAWR to be enabled in a KVM guest, the DAWR needs to be force
enabled in the host AND the guest. For this reason, this won't work on
POWERVM as it doesn't allow the HCALL to work. Writes of 'Y' to the
dawr_enable_dangerous file will fail if the hypervisor doesn't support
writing the DAWR.
To double check the DAWR is working, run this kernel selftest:
tools/testing/selftests/powerpc/ptrace/ptrace-hwbreak.c
Any errors/failures/skips mean something is wrong.
Signed-off-by: Michael Neuling <mikey@neuling.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
108 lines
3.5 KiB
C
108 lines
3.5 KiB
C
/*
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* PowerPC BookIII S hardware breakpoint definitions
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*
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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 2 of the License, or
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* (at your option) any later version.
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*
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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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*
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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, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright 2010, IBM Corporation.
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* Author: K.Prasad <prasad@linux.vnet.ibm.com>
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*
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*/
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#ifndef _PPC_BOOK3S_64_HW_BREAKPOINT_H
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#define _PPC_BOOK3S_64_HW_BREAKPOINT_H
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#ifdef __KERNEL__
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struct arch_hw_breakpoint {
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unsigned long address;
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u16 type;
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u16 len; /* length of the target data symbol */
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};
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/* Note: Don't change the the first 6 bits below as they are in the same order
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* as the dabr and dabrx.
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*/
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#define HW_BRK_TYPE_READ 0x01
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#define HW_BRK_TYPE_WRITE 0x02
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#define HW_BRK_TYPE_TRANSLATE 0x04
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#define HW_BRK_TYPE_USER 0x08
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#define HW_BRK_TYPE_KERNEL 0x10
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#define HW_BRK_TYPE_HYP 0x20
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#define HW_BRK_TYPE_EXTRANEOUS_IRQ 0x80
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/* bits that overlap with the bottom 3 bits of the dabr */
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#define HW_BRK_TYPE_RDWR (HW_BRK_TYPE_READ | HW_BRK_TYPE_WRITE)
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#define HW_BRK_TYPE_DABR (HW_BRK_TYPE_RDWR | HW_BRK_TYPE_TRANSLATE)
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#define HW_BRK_TYPE_PRIV_ALL (HW_BRK_TYPE_USER | HW_BRK_TYPE_KERNEL | \
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HW_BRK_TYPE_HYP)
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#ifdef CONFIG_HAVE_HW_BREAKPOINT
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#include <linux/kdebug.h>
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#include <asm/reg.h>
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#include <asm/debug.h>
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struct perf_event_attr;
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struct perf_event;
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struct pmu;
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struct perf_sample_data;
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struct task_struct;
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#define HW_BREAKPOINT_ALIGN 0x7
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extern int hw_breakpoint_slots(int type);
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extern int arch_bp_generic_fields(int type, int *gen_bp_type);
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extern int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw);
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extern int hw_breakpoint_arch_parse(struct perf_event *bp,
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const struct perf_event_attr *attr,
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struct arch_hw_breakpoint *hw);
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extern int hw_breakpoint_exceptions_notify(struct notifier_block *unused,
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unsigned long val, void *data);
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int arch_install_hw_breakpoint(struct perf_event *bp);
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void arch_uninstall_hw_breakpoint(struct perf_event *bp);
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void arch_unregister_hw_breakpoint(struct perf_event *bp);
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void hw_breakpoint_pmu_read(struct perf_event *bp);
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extern void flush_ptrace_hw_breakpoint(struct task_struct *tsk);
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extern struct pmu perf_ops_bp;
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extern void ptrace_triggered(struct perf_event *bp,
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struct perf_sample_data *data, struct pt_regs *regs);
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static inline void hw_breakpoint_disable(void)
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{
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struct arch_hw_breakpoint brk;
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brk.address = 0;
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brk.type = 0;
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brk.len = 0;
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if (ppc_breakpoint_available())
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__set_breakpoint(&brk);
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}
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extern void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs);
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int hw_breakpoint_handler(struct die_args *args);
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extern int set_dawr(struct arch_hw_breakpoint *brk);
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extern bool dawr_force_enable;
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static inline bool dawr_enabled(void)
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{
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return dawr_force_enable;
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}
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#else /* CONFIG_HAVE_HW_BREAKPOINT */
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static inline void hw_breakpoint_disable(void) { }
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static inline void thread_change_pc(struct task_struct *tsk,
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struct pt_regs *regs) { }
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static inline bool dawr_enabled(void) { return false; }
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#endif /* CONFIG_HAVE_HW_BREAKPOINT */
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#endif /* __KERNEL__ */
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#endif /* _PPC_BOOK3S_64_HW_BREAKPOINT_H */
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