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powerpc, hw_breakpoints: Implement hw_breakpoints for 64-bit server processors

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Implement perf-events based hw-breakpoint interfaces for PowerPC
64-bit server (Book III S) processors.  This allows access to a
given location to be used as an event that can be counted or
profiled by the perf_events subsystem.

This is done using the DABR (data breakpoint register), which can
also be used for process debugging via ptrace.  When perf_event
hw_breakpoint support is configured in, the perf_event subsystem
manages the DABR and arbitrates access to it, and ptrace then
creates a perf_event when it is requested to set a data breakpoint.

[Adopted suggestions from Paul Mackerras <paulus@samba.org> to
- emulate_step() all system-wide breakpoints and single-step only the
  per-task breakpoints
- perform arch-specific cleanup before unregistration through
  arch_unregister_hw_breakpoint()
]

Signed-off-by: K.Prasad <prasad@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>
This commit is contained in:
K.Prasad
2010-06-15 11:35:19 +05:30
committed by Paul Mackerras
parent f7136c5150
commit 5aae8a5370
11 changed files with 495 additions and 0 deletions
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64
arch/powerpc/kernel/ptrace.c
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@@ -32,6 +32,8 @@
#ifdef CONFIG_PPC32
#include <linux/module.h>
#endif
#include <linux/hw_breakpoint.h>
#include <linux/perf_event.h>
#include <asm/uaccess.h>
#include <asm/page.h>
@@ -866,9 +868,34 @@ void user_disable_single_step(struct task_struct *task)
clear_tsk_thread_flag(task, TIF_SINGLESTEP);
}
#ifdef CONFIG_HAVE_HW_BREAKPOINT
void ptrace_triggered(struct perf_event *bp, int nmi,
struct perf_sample_data *data, struct pt_regs *regs)
{
struct perf_event_attr attr;
/*
* Disable the breakpoint request here since ptrace has defined a
* one-shot behaviour for breakpoint exceptions in PPC64.
* The SIGTRAP signal is generated automatically for us in do_dabr().
* We don't have to do anything about that here
*/
attr = bp->attr;
attr.disabled = true;
modify_user_hw_breakpoint(bp, &attr);
}
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
unsigned long data)
{
#ifdef CONFIG_HAVE_HW_BREAKPOINT
int ret;
struct thread_struct *thread = &(task->thread);
struct perf_event *bp;
struct perf_event_attr attr;
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
/* For ppc64 we support one DABR and no IABR's at the moment (ppc64).
* For embedded processors we support one DAC and no IAC's at the
* moment.
@@ -896,6 +923,43 @@ int ptrace_set_debugreg(struct task_struct *task, unsigned long addr,
/* Ensure breakpoint translation bit is set */
if (data && !(data & DABR_TRANSLATION))
return -EIO;
#ifdef CONFIG_HAVE_HW_BREAKPOINT
bp = thread->ptrace_bps[0];
if ((!data) || !(data & (DABR_DATA_WRITE | DABR_DATA_READ))) {
if (bp) {
unregister_hw_breakpoint(bp);
thread->ptrace_bps[0] = NULL;
}
return 0;
}
if (bp) {
attr = bp->attr;
attr.bp_addr = data & ~HW_BREAKPOINT_ALIGN;
arch_bp_generic_fields(data &
(DABR_DATA_WRITE | DABR_DATA_READ),
&attr.bp_type);
ret = modify_user_hw_breakpoint(bp, &attr);
if (ret)
return ret;
thread->ptrace_bps[0] = bp;
thread->dabr = data;
return 0;
}
/* Create a new breakpoint request if one doesn't exist already */
hw_breakpoint_init(&attr);
attr.bp_addr = data & ~HW_BREAKPOINT_ALIGN;
arch_bp_generic_fields(data & (DABR_DATA_WRITE | DABR_DATA_READ),
&attr.bp_type);
thread->ptrace_bps[0] = bp = register_user_hw_breakpoint(&attr,
ptrace_triggered, task);
if (IS_ERR(bp)) {
thread->ptrace_bps[0] = NULL;
return PTR_ERR(bp);
}
#endif /* CONFIG_HAVE_HW_BREAKPOINT */
/* Move contents to the DABR register */
task->thread.dabr = data;