From 62edab9056a6cf0c9207339c8892c923a5217e45 Mon Sep 17 00:00:00 2001 From: "K.Prasad" Date: Mon, 1 Jun 2009 23:47:06 +0530 Subject: [PATCH] hw-breakpoints: reset bits in dr6 after the corresponding exception is handled This patch resets the bit in dr6 after the corresponding exception is handled in code, so that we keep a clean track of the current virtual debug status register. [ Impact: keep track of breakpoints triggering completion ] Signed-off-by: K.Prasad Signed-off-by: Frederic Weisbecker --- arch/x86/kernel/hw_breakpoint.c | 13 +++++++++++-- arch/x86/kernel/kgdb.c | 6 ++++++ arch/x86/kernel/kprobes.c | 9 ++++++++- arch/x86/kernel/traps.c | 4 ++-- arch/x86/mm/kmmio.c | 8 +++++++- 5 files changed, 34 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/hw_breakpoint.c b/arch/x86/kernel/hw_breakpoint.c index 4867c9f..6945147 100644 --- a/arch/x86/kernel/hw_breakpoint.c +++ b/arch/x86/kernel/hw_breakpoint.c @@ -314,8 +314,12 @@ int __kprobes hw_breakpoint_handler(struct die_args *args) { int i, cpu, rc = NOTIFY_STOP; struct hw_breakpoint *bp; - /* The DR6 value is stored in args->err */ - unsigned long dr7, dr6 = args->err; + unsigned long dr7, dr6; + unsigned long *dr6_p; + + /* The DR6 value is pointed by args->err */ + dr6_p = (unsigned long *)ERR_PTR(args->err); + dr6 = *dr6_p; /* Do an early return if no trap bits are set in DR6 */ if ((dr6 & DR_TRAP_BITS) == 0) @@ -352,6 +356,11 @@ int __kprobes hw_breakpoint_handler(struct die_args *args) rc = NOTIFY_DONE; } /* + * Reset the 'i'th TRAP bit in dr6 to denote completion of + * exception handling + */ + (*dr6_p) &= ~(DR_TRAP0 << i); + /* * bp can be NULL due to lazy debug register switching * or due to the delay between updates of hbp_kernel_pos * and this_hbp_kernel. diff --git a/arch/x86/kernel/kgdb.c b/arch/x86/kernel/kgdb.c index b1f4dff..f820b73 100644 --- a/arch/x86/kernel/kgdb.c +++ b/arch/x86/kernel/kgdb.c @@ -43,6 +43,7 @@ #include #include +#include #include #include @@ -434,6 +435,11 @@ single_step_cont(struct pt_regs *regs, struct die_args *args) "resuming...\n"); kgdb_arch_handle_exception(args->trapnr, args->signr, args->err, "c", "", regs); + /* + * Reset the BS bit in dr6 (pointed by args->err) to + * denote completion of processing + */ + (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP; return NOTIFY_STOP; } diff --git a/arch/x86/kernel/kprobes.c b/arch/x86/kernel/kprobes.c index 7b5169d..b5b1848 100644 --- a/arch/x86/kernel/kprobes.c +++ b/arch/x86/kernel/kprobes.c @@ -54,6 +54,7 @@ #include #include #include +#include void jprobe_return_end(void); @@ -967,8 +968,14 @@ int __kprobes kprobe_exceptions_notify(struct notifier_block *self, ret = NOTIFY_STOP; break; case DIE_DEBUG: - if (post_kprobe_handler(args->regs)) + if (post_kprobe_handler(args->regs)) { + /* + * Reset the BS bit in dr6 (pointed by args->err) to + * denote completion of processing + */ + (*(unsigned long *)ERR_PTR(args->err)) &= ~DR_STEP; ret = NOTIFY_STOP; + } break; case DIE_GPF: /* diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index de99132..124a4d5 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -545,8 +545,8 @@ dotraplinkage void __kprobes do_debug(struct pt_regs *regs, long error_code) /* Store the virtualized DR6 value */ tsk->thread.debugreg6 = dr6; - if (notify_die(DIE_DEBUG, "debug", regs, dr6, error_code, - SIGTRAP) == NOTIFY_STOP) + if (notify_die(DIE_DEBUG, "debug", regs, PTR_ERR(&dr6), error_code, + SIGTRAP) == NOTIFY_STOP) return; /* It's safe to allow irq's after DR6 has been saved */ diff --git a/arch/x86/mm/kmmio.c b/arch/x86/mm/kmmio.c index 16ccbd7..11a4ad4 100644 --- a/arch/x86/mm/kmmio.c +++ b/arch/x86/mm/kmmio.c @@ -540,8 +540,14 @@ kmmio_die_notifier(struct notifier_block *nb, unsigned long val, void *args) struct die_args *arg = args; if (val == DIE_DEBUG && (arg->err & DR_STEP)) - if (post_kmmio_handler(arg->err, arg->regs) == 1) + if (post_kmmio_handler(arg->err, arg->regs) == 1) { + /* + * Reset the BS bit in dr6 (pointed by args->err) to + * denote completion of processing + */ + (*(unsigned long *)ERR_PTR(arg->err)) &= ~DR_STEP; return NOTIFY_STOP; + } return NOTIFY_DONE; } -- 2.7.4