| Message ID | 1382008671-4515-2-git-send-email-sandeepa.prabhu@linaro.org |
|---|---|
| State | New |
| Headers | show |
Hi Sandeepa, This is getting there, thanks for persevering with it. I still have a few minor comments though. On Thu, Oct 17, 2013 at 12:17:46PM +0100, Sandeepa Prabhu wrote: > AArch64 Single Steping and Breakpoint debug exceptions will be > used by multiple debug framworks like kprobes & kgdb. > > This patch implements the hooks for those frameworks to register > their own handlers for handling breakpoint and single step events. > > Reworked the debug exception handler in entry.S: do_dbg to route > software breakpoint (BRK64) exception to do_debug_exception() > > Signed-off-by: Sandeepa Prabhu <sandeepa.prabhu@linaro.org> > Signed-off-by: Deepak Saxena <dsaxena@linaro.org> > --- > arch/arm64/include/asm/debug-monitors.h | 21 ++++++++ > arch/arm64/kernel/debug-monitors.c | 86 ++++++++++++++++++++++++++++++++- > arch/arm64/kernel/entry.S | 2 + > 3 files changed, 108 insertions(+), 1 deletion(-) [...] > @@ -215,7 +257,10 @@ static int single_step_handler(unsigned long addr, unsigned int esr, > */ > user_rewind_single_step(current); > } else { > - /* TODO: route to KGDB */ > + /* call registered single step handlers */ Don't bother with this comment (it's crystal clear from the code). > + if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED) > + return 0; > + > pr_warning("Unexpected kernel single-step exception at EL1\n"); > /* > * Re-enable stepping since we know that we will be > @@ -227,11 +272,50 @@ static int single_step_handler(unsigned long addr, unsigned int esr, > return 0; > } > > + > +static LIST_HEAD(break_hook); > +DEFINE_RWLOCK(break_hook_lock); This guy can be a plain old spinlock. That way, the readers have less overhead but things still work because we only call a single hook function. Will
Hi Will, Sorry for responding to this after long-time, I missed this review during Linaro connect travels. On 25 October 2013 20:52, Will Deacon <will.deacon@arm.com> wrote: > Hi Sandeepa, > > This is getting there, thanks for persevering with it. I still have a few > minor comments though. > > On Thu, Oct 17, 2013 at 12:17:46PM +0100, Sandeepa Prabhu wrote: >> AArch64 Single Steping and Breakpoint debug exceptions will be >> used by multiple debug framworks like kprobes & kgdb. >> >> This patch implements the hooks for those frameworks to register >> their own handlers for handling breakpoint and single step events. >> >> Reworked the debug exception handler in entry.S: do_dbg to route >> software breakpoint (BRK64) exception to do_debug_exception() >> >> Signed-off-by: Sandeepa Prabhu <sandeepa.prabhu@linaro.org> >> Signed-off-by: Deepak Saxena <dsaxena@linaro.org> >> --- >> arch/arm64/include/asm/debug-monitors.h | 21 ++++++++ >> arch/arm64/kernel/debug-monitors.c | 86 ++++++++++++++++++++++++++++++++- >> arch/arm64/kernel/entry.S | 2 + >> 3 files changed, 108 insertions(+), 1 deletion(-) > > [...] > >> @@ -215,7 +257,10 @@ static int single_step_handler(unsigned long addr, unsigned int esr, >> */ >> user_rewind_single_step(current); >> } else { >> - /* TODO: route to KGDB */ >> + /* call registered single step handlers */ > > Don't bother with this comment (it's crystal clear from the code). OK, I will remove this unnecessary print. > >> + if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED) >> + return 0; >> + >> pr_warning("Unexpected kernel single-step exception at EL1\n"); >> /* >> * Re-enable stepping since we know that we will be >> @@ -227,11 +272,50 @@ static int single_step_handler(unsigned long addr, unsigned int esr, >> return 0; >> } >> >> + >> +static LIST_HEAD(break_hook); >> +DEFINE_RWLOCK(break_hook_lock); > > This guy can be a plain old spinlock. That way, the readers have less > overhead but things still work because we only call a single hook function. well, kprobes need to support recursive breakpoints (i.e. breakpoint handler executing BRK once again) so I converted this lock to rw_lock. I should put this info in commit description to be more clearer. Let me know if you find any issue with re-cursing in breakpoint exception? Thanks, Sandeepa > > Will > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/
On Tue, Dec 03, 2013 at 02:33:17PM +0000, Sandeepa Prabhu wrote: > Hi Will, > > Sorry for responding to this after long-time, I missed this review > during Linaro connect travels. No problem. > >> @@ -215,7 +257,10 @@ static int single_step_handler(unsigned long addr, unsigned int esr, > >> */ > >> user_rewind_single_step(current); > >> } else { > >> - /* TODO: route to KGDB */ > >> + /* call registered single step handlers */ > > > > Don't bother with this comment (it's crystal clear from the code). > OK, I will remove this unnecessary print. Thanks. > >> +static LIST_HEAD(break_hook); > >> +DEFINE_RWLOCK(break_hook_lock); > > > > This guy can be a plain old spinlock. That way, the readers have less > > overhead but things still work because we only call a single hook function. > well, kprobes need to support recursive breakpoints (i.e. breakpoint > handler executing BRK once again) > so I converted this lock to rw_lock. I should put this info in commit > description to be more clearer. Actually, this is one place where a comment in the code *would* be useful! > Let me know if you find any issue with re-cursing in breakpoint exception? Sounds ok to me. With those changes: Acked-by: Will Deacon <will.deacon@arm.com> Cheers, Will
diff --git a/arch/arm64/include/asm/debug-monitors.h b/arch/arm64/include/asm/debug-monitors.h index a2232d0..6231479 100644 --- a/arch/arm64/include/asm/debug-monitors.h +++ b/arch/arm64/include/asm/debug-monitors.h @@ -62,6 +62,27 @@ struct task_struct; #define DBG_ARCH_ID_RESERVED 0 /* In case of ptrace ABI updates. */ +#define DBG_HOOK_HANDLED 0 +#define DBG_HOOK_ERROR 1 + +struct step_hook { + struct list_head node; + int (*fn)(struct pt_regs *regs, unsigned int esr); +}; + +void register_step_hook(struct step_hook *hook); +void unregister_step_hook(struct step_hook *hook); + +struct break_hook { + struct list_head node; + u32 esr_val; + u32 esr_mask; + int (*fn)(struct pt_regs *regs, unsigned int esr); +}; + +void register_break_hook(struct break_hook *hook); +void unregister_break_hook(struct break_hook *hook); + u8 debug_monitors_arch(void); void enable_debug_monitors(enum debug_el el); diff --git a/arch/arm64/kernel/debug-monitors.c b/arch/arm64/kernel/debug-monitors.c index cbfacf7..e42ad5f 100644 --- a/arch/arm64/kernel/debug-monitors.c +++ b/arch/arm64/kernel/debug-monitors.c @@ -188,6 +188,48 @@ static void clear_regs_spsr_ss(struct pt_regs *regs) regs->pstate = spsr; } +/* EL1 Single Step Handler hooks */ +static LIST_HEAD(step_hook); +DEFINE_RWLOCK(step_hook_lock); + +void register_step_hook(struct step_hook *hook) +{ + write_lock(&step_hook_lock); + list_add(&hook->node, &step_hook); + write_unlock(&step_hook_lock); +} + +void unregister_step_hook(struct step_hook *hook) +{ + write_lock(&step_hook_lock); + list_del(&hook->node); + write_unlock(&step_hook_lock); +} + +/* + * Call registered single step handers + * There is no Syndrome info to check for determining the handler. + * So we call all the registered handlers, until the right handler is + * found which returns zero. + */ +static int call_step_hook(struct pt_regs *regs, unsigned int esr) +{ + struct step_hook *hook; + int retval = DBG_HOOK_ERROR; + + read_lock(&step_hook_lock); + + list_for_each_entry(hook, &step_hook, node) { + retval = hook->fn(regs, esr); + if (retval == DBG_HOOK_HANDLED) + break; + } + + read_unlock(&step_hook_lock); + + return retval; +} + static int single_step_handler(unsigned long addr, unsigned int esr, struct pt_regs *regs) { @@ -215,7 +257,10 @@ static int single_step_handler(unsigned long addr, unsigned int esr, */ user_rewind_single_step(current); } else { - /* TODO: route to KGDB */ + /* call registered single step handlers */ + if (call_step_hook(regs, esr) == DBG_HOOK_HANDLED) + return 0; + pr_warning("Unexpected kernel single-step exception at EL1\n"); /* * Re-enable stepping since we know that we will be @@ -227,11 +272,50 @@ static int single_step_handler(unsigned long addr, unsigned int esr, return 0; } + +static LIST_HEAD(break_hook); +DEFINE_RWLOCK(break_hook_lock); + +void register_break_hook(struct break_hook *hook) +{ + write_lock(&break_hook_lock); + list_add(&hook->node, &break_hook); + write_unlock(&break_hook_lock); +} + +void unregister_break_hook(struct break_hook *hook) +{ + write_lock(&break_hook_lock); + list_del(&hook->node); + write_unlock(&break_hook_lock); +} + +static int call_break_hook(struct pt_regs *regs, unsigned int esr) +{ + struct break_hook *hook; + int (*fn)(struct pt_regs *regs, unsigned int esr) = NULL; + + read_lock(&break_hook_lock); + list_for_each_entry(hook, &break_hook, node) + if ((esr & hook->esr_mask) == hook->esr_val) + fn = hook->fn; + read_unlock(&break_hook_lock); + + return fn ? fn(regs, esr) : DBG_HOOK_ERROR; +} + static int brk_handler(unsigned long addr, unsigned int esr, struct pt_regs *regs) { siginfo_t info; + /* call the registered breakpoint handler */ + if (call_break_hook(regs, esr) == DBG_HOOK_HANDLED) + return 0; + + pr_warn("unexpected brk exception at %lx, esr=0x%x\n", + (long)instruction_pointer(regs), esr); + if (!user_mode(regs)) return -EFAULT; diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 3881fd1..7fbc510 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -288,6 +288,8 @@ el1_dbg: /* * Debug exception handling */ + cmp x24, #ESR_EL1_EC_BRK64 // if BRK64 + cinc x24, x24, eq // set bit '0' tbz x24, #0, el1_inv // EL1 only mrs x0, far_el1 mov x2, sp // struct pt_regs