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    Subject[PATCH 3/6] x86: Allow the user not to build hw_breakpoints
    Date
    So that hw_breakpoints and perf can be not built on
    specific embedded systems.

    Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Ingo Molnar <mingo@elte.hu>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Jason Wessel <jason.wessel@windriver.com>
    Cc: H. Peter Anvin <hpa@zytor.com>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    ---
    arch/x86/Kconfig | 3 +--
    arch/x86/include/asm/debugreg.h | 33 +++++++++++++++++++++++++++++++--
    arch/x86/kernel/Makefile | 3 ++-
    arch/x86/kernel/process.c | 1 +
    arch/x86/kernel/ptrace.c | 17 +++++++++++++++++
    5 files changed, 52 insertions(+), 5 deletions(-)

    diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
    index 8b49bff..fb28dd9 100644
    --- a/arch/x86/Kconfig
    +++ b/arch/x86/Kconfig
    @@ -41,7 +41,7 @@ config X86
    select HAVE_FTRACE_NMI_ENTER if DYNAMIC_FTRACE
    select HAVE_SYSCALL_TRACEPOINTS
    select HAVE_KVM
    - select HAVE_ARCH_KGDB
    + select HAVE_ARCH_KGDB if HW_BREAKPOINT
    select HAVE_ARCH_TRACEHOOK
    select HAVE_GENERIC_DMA_COHERENT if X86_32
    select HAVE_EFFICIENT_UNALIGNED_ACCESS
    @@ -54,7 +54,6 @@ config X86
    select HAVE_KERNEL_XZ
    select HAVE_KERNEL_LZO
    select HAVE_HW_BREAKPOINT
    - select HW_BREAKPOINT
    select HAVE_MIXED_BREAKPOINTS_REGS
    select PERF_EVENTS
    select HAVE_PERF_EVENTS_NMI
    diff --git a/arch/x86/include/asm/debugreg.h b/arch/x86/include/asm/debugreg.h
    index 078ad0c..c40d6d4 100644
    --- a/arch/x86/include/asm/debugreg.h
    +++ b/arch/x86/include/asm/debugreg.h
    @@ -78,8 +78,6 @@
    */
    #ifdef __KERNEL__

    -DECLARE_PER_CPU(unsigned long, cpu_dr7);
    -
    static inline void hw_breakpoint_disable(void)
    {
    /* Zero the control register for HW Breakpoint */
    @@ -92,6 +90,10 @@ static inline void hw_breakpoint_disable(void)
    set_debugreg(0UL, 3);
    }

    +#ifdef CONFIG_HW_BREAKPOINT
    +
    +DECLARE_PER_CPU(unsigned long, cpu_dr7);
    +
    static inline int hw_breakpoint_active(void)
    {
    return __this_cpu_read(cpu_dr7) & DR_GLOBAL_ENABLE_MASK;
    @@ -100,6 +102,33 @@ static inline int hw_breakpoint_active(void)
    extern void aout_dump_debugregs(struct user *dump);

    extern void hw_breakpoint_restore(void);
    +#else
    +static inline int hw_breakpoint_active(void)
    +{
    + return 0;
    +}
    +
    +static inline void hw_breakpoint_restore(void)
    +{
    + set_debugreg(0UL, 0);
    + set_debugreg(0UL, 1);
    + set_debugreg(0UL, 2);
    + set_debugreg(0UL, 3);
    + set_debugreg(current->thread.debugreg6, 6);
    + set_debugreg(0UL, 7);
    +}
    +
    +static inline void aout_dump_debugregs(struct user *dump)
    +{
    + int i;
    +
    + for (i = 0; i < 6; i++)
    + dump->u_debugreg[i] = 0;
    +
    + dump->u_debugreg[6] = current->thread.debugreg6;
    + dump->u_debugreg[7] = 0;
    +}
    +#endif /* CONFIG_HW_BREAKPOINT */

    #endif /* __KERNEL__ */

    diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
    index 7338ef2..270e439 100644
    --- a/arch/x86/kernel/Makefile
    +++ b/arch/x86/kernel/Makefile
    @@ -42,7 +42,7 @@ obj-$(CONFIG_X86_64) += sys_x86_64.o x8664_ksyms_64.o
    obj-$(CONFIG_X86_64) += syscall_64.o vsyscall_64.o
    obj-y += bootflag.o e820.o
    obj-y += pci-dma.o quirks.o topology.o kdebugfs.o
    -obj-y += alternative.o i8253.o pci-nommu.o hw_breakpoint.o
    +obj-y += alternative.o i8253.o pci-nommu.o
    obj-y += tsc.o io_delay.o rtc.o
    obj-y += pci-iommu_table.o
    obj-y += resource.o
    @@ -51,6 +51,7 @@ obj-y += trampoline.o trampoline_$(BITS).o
    obj-y += process.o
    obj-y += i387.o xsave.o
    obj-y += ptrace.o
    +obj-$(CONFIG_HW_BREAKPOINT) += hw_breakpoint.o
    obj-$(CONFIG_X86_32) += tls.o
    obj-$(CONFIG_IA32_EMULATION) += tls.o
    obj-y += step.o
    diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
    index d46cbe4..d1adbd1 100644
    --- a/arch/x86/kernel/process.c
    +++ b/arch/x86/kernel/process.c
    @@ -22,6 +22,7 @@
    #include <asm/uaccess.h>
    #include <asm/i387.h>
    #include <asm/debugreg.h>
    +#include <asm/kdebug.h>

    struct kmem_cache *task_xstate_cachep;
    EXPORT_SYMBOL_GPL(task_xstate_cachep);
    diff --git a/arch/x86/kernel/ptrace.c b/arch/x86/kernel/ptrace.c
    index f65e5b5..091f110c 100644
    --- a/arch/x86/kernel/ptrace.c
    +++ b/arch/x86/kernel/ptrace.c
    @@ -528,6 +528,7 @@ static int genregs_set(struct task_struct *target,
    return ret;
    }

    +#ifdef CONFIG_HW_BREAKPOINT
    static void ptrace_triggered(struct perf_event *bp, int nmi,
    struct perf_sample_data *data,
    struct pt_regs *regs)
    @@ -777,6 +778,22 @@ ret_path:
    return rc;
    }

    +#else /* !CONFIG_HW_BREAKPOINT */
    +
    +static inline unsigned long
    +ptrace_get_debugreg(struct task_struct *tsk, int n)
    +{
    + return -ENOSYS;
    +}
    +
    +static inline
    +int ptrace_set_debugreg(struct task_struct *tsk, int n, unsigned long val)
    +{
    + return -ENOSYS;
    +}
    +
    +#endif /* CONFIG_HW_BREAKPOINT */
    +
    /*
    * These access the current or another (stopped) task's io permission
    * bitmap for debugging or core dump.
    --
    1.7.3.2


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