Messages in this thread |  | | | Date | Mon, 17 Oct 2005 22:49:30 -0700 | | From | "Paul E. McKenney" <> | | Subject | Re: [PATCH 9/9] Kprobes: Use RCU for (un)register synchronization - arch changes |
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On Mon, Oct 10, 2005 at 10:48:13AM -0400, Ananth N Mavinakayanahalli wrote: > From: Ananth N Mavinakayanahalli <ananth@in.ibm.com> > > Changes to the arch kprobes infrastructure to take advantage of the locking > changes introduced by usage of RCU for synchronization. All handlers are > now run without any locks held, so they have to be re-entrant or provide > their own synchronization.
And a few very similar questions here as well...
Thanx, Paul
> Signed-off-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com> > Signed-off-by: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com> > --- > > arch/i386/kernel/kprobes.c | 22 +++++++--------------- > arch/ia64/kernel/kprobes.c | 16 ++++++---------- > arch/ppc64/kernel/kprobes.c | 24 ++++++------------------ > arch/sparc64/kernel/kprobes.c | 14 ++------------ > arch/x86_64/kernel/kprobes.c | 25 ++++++------------------- > 5 files changed, 27 insertions(+), 74 deletions(-) > > Index: linux-2.6.14-rc3/arch/i386/kernel/kprobes.c > =================================================================== > --- linux-2.6.14-rc3.orig/arch/i386/kernel/kprobes.c 2005-10-05 16:08:13.000000000 -0400 > +++ linux-2.6.14-rc3/arch/i386/kernel/kprobes.c 2005-10-05 16:08:48.000000000 -0400 > @@ -31,7 +31,6 @@ > #include <linux/config.h> > #include <linux/kprobes.h> > #include <linux/ptrace.h> > -#include <linux/spinlock.h> > #include <linux/preempt.h> > #include <asm/cacheflush.h> > #include <asm/kdebug.h> > @@ -123,6 +122,7 @@ static inline void prepare_singlestep(st > regs->eip = (unsigned long)&p->ainsn.insn; > } > > +/* Called with kretprobe_lock held */ > void __kprobes arch_prepare_kretprobe(struct kretprobe *rp, > struct pt_regs *regs) > { > @@ -168,15 +168,12 @@ static int __kprobes kprobe_handler(stru > } > /* Check we're not actually recursing */ > if (kprobe_running()) { > - /* We *are* holding lock here, so this is safe. > - Disarm the probe we just hit, and ignore it. */ > p = get_kprobe(addr); > if (p) { > if (kcb->kprobe_status == KPROBE_HIT_SS && > *p->ainsn.insn == BREAKPOINT_INSTRUCTION) { > regs->eflags &= ~TF_MASK; > regs->eflags |= kcb->kprobe_saved_eflags; > - unlock_kprobes(); > goto no_kprobe; > } > /* We have reentered the kprobe_handler(), since > @@ -197,14 +194,11 @@ static int __kprobes kprobe_handler(stru > goto ss_probe; > } > } > - /* If it's not ours, can't be delete race, (we hold lock). */ > goto no_kprobe; > } > > - lock_kprobes(); > p = get_kprobe(addr); > if (!p) { > - unlock_kprobes(); > if (regs->eflags & VM_MASK) { > /* We are in virtual-8086 mode. Return 0 */ > goto no_kprobe; > @@ -268,9 +262,10 @@ int __kprobes trampoline_probe_handler(s > struct kretprobe_instance *ri = NULL; > struct hlist_head *head; > struct hlist_node *node, *tmp; > - unsigned long orig_ret_address = 0; > + unsigned long flags, orig_ret_address = 0; > unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline; > > + spin_lock_irqsave(&kretprobe_lock, flags); > head = kretprobe_inst_table_head(current); > > /* > @@ -310,7 +305,7 @@ int __kprobes trampoline_probe_handler(s > regs->eip = orig_ret_address; > > reset_current_kprobe(); > - unlock_kprobes(); > + spin_unlock_irqrestore(&kretprobe_lock, flags); > preempt_enable_no_resched(); > > /* > @@ -395,7 +390,7 @@ static void __kprobes resume_execution(s > > /* > * Interrupts are disabled on entry as trap1 is an interrupt gate and they > - * remain disabled thoroughout this function. And we hold kprobe lock. > + * remain disabled thoroughout this function. > */ > static inline int post_kprobe_handler(struct pt_regs *regs) > { > @@ -419,7 +414,6 @@ static inline int post_kprobe_handler(st > goto out; > } > reset_current_kprobe(); > - unlock_kprobes(); > out: > preempt_enable_no_resched(); > > @@ -434,7 +428,6 @@ out: > return 1; > } > > -/* Interrupts disabled, kprobe_lock held. */ > static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr) > { > struct kprobe *cur = kprobe_running(); > @@ -448,7 +441,6 @@ static inline int kprobe_fault_handler(s > regs->eflags |= kcb->kprobe_old_eflags; > > reset_current_kprobe(); > - unlock_kprobes(); > preempt_enable_no_resched(); > } > return 0; > @@ -463,7 +455,7 @@ int __kprobes kprobe_exceptions_notify(s > struct die_args *args = (struct die_args *)data; > int ret = NOTIFY_DONE; > > - preempt_disable(); > + rcu_read_lock();
If synchronize_sched() is used on the update side, this needs to remain preempt_disable() rather than rcu_read_lock().
> switch (val) { > case DIE_INT3: > if (kprobe_handler(args->regs)) > @@ -482,7 +474,7 @@ int __kprobes kprobe_exceptions_notify(s > default: > break; > } > - preempt_enable(); > + rcu_read_unlock(); > return ret; > } > > Index: linux-2.6.14-rc3/arch/ia64/kernel/kprobes.c > =================================================================== > --- linux-2.6.14-rc3.orig/arch/ia64/kernel/kprobes.c 2005-10-05 16:08:14.000000000 -0400 > +++ linux-2.6.14-rc3/arch/ia64/kernel/kprobes.c 2005-10-05 16:08:48.000000000 -0400 > @@ -26,7 +26,6 @@ > #include <linux/config.h> > #include <linux/kprobes.h> > #include <linux/ptrace.h> > -#include <linux/spinlock.h> > #include <linux/string.h> > #include <linux/slab.h> > #include <linux/preempt.h> > @@ -343,10 +342,11 @@ int __kprobes trampoline_probe_handler(s > struct kretprobe_instance *ri = NULL; > struct hlist_head *head; > struct hlist_node *node, *tmp; > - unsigned long orig_ret_address = 0; > + unsigned long flags, orig_ret_address = 0; > unsigned long trampoline_address = > ((struct fnptr *)kretprobe_trampoline)->ip; > > + spin_lock_irqsave(&kretprobe_lock, flags); > head = kretprobe_inst_table_head(current); > > /* > @@ -386,7 +386,7 @@ int __kprobes trampoline_probe_handler(s > regs->cr_iip = orig_ret_address; > > reset_current_kprobe(); > - unlock_kprobes(); > + spin_unlock_irqrestore(&kretprobe_lock, flags); > preempt_enable_no_resched(); > > /* > @@ -397,6 +397,7 @@ int __kprobes trampoline_probe_handler(s > return 1; > } > > +/* Called with kretprobe_lock held */ > void __kprobes arch_prepare_kretprobe(struct kretprobe *rp, > struct pt_regs *regs) > { > @@ -612,7 +613,6 @@ static int __kprobes pre_kprobes_handler > if ((kcb->kprobe_status == KPROBE_HIT_SS) && > (p->ainsn.inst_flag == INST_FLAG_BREAK_INST)) { > ia64_psr(regs)->ss = 0; > - unlock_kprobes(); > goto no_kprobe; > } > /* We have reentered the pre_kprobe_handler(), since > @@ -641,10 +641,8 @@ static int __kprobes pre_kprobes_handler > } > } > > - lock_kprobes(); > p = get_kprobe(addr); > if (!p) { > - unlock_kprobes(); > if (!is_ia64_break_inst(regs)) { > /* > * The breakpoint instruction was removed right > @@ -707,7 +705,6 @@ static int __kprobes post_kprobes_handle > goto out; > } > reset_current_kprobe(); > - unlock_kprobes(); > > out: > preempt_enable_no_resched(); > @@ -728,7 +725,6 @@ static int __kprobes kprobes_fault_handl > if (kcb->kprobe_status & KPROBE_HIT_SS) { > resume_execution(cur, regs); > reset_current_kprobe(); > - unlock_kprobes(); > preempt_enable_no_resched(); > } > > @@ -741,7 +737,7 @@ int __kprobes kprobe_exceptions_notify(s > struct die_args *args = (struct die_args *)data; > int ret = NOTIFY_DONE; > > - preempt_disable(); > + rcu_read_lock();
Ditto here...
> switch(val) { > case DIE_BREAK: > if (pre_kprobes_handler(args)) > @@ -757,7 +753,7 @@ int __kprobes kprobe_exceptions_notify(s > default: > break; > } > - preempt_enable(); > + rcu_read_unlock(); > return ret; > } > > Index: linux-2.6.14-rc3/arch/ppc64/kernel/kprobes.c > =================================================================== > --- linux-2.6.14-rc3.orig/arch/ppc64/kernel/kprobes.c 2005-10-05 16:08:15.000000000 -0400 > +++ linux-2.6.14-rc3/arch/ppc64/kernel/kprobes.c 2005-10-05 16:08:48.000000000 -0400 > @@ -30,7 +30,6 @@ > #include <linux/config.h> > #include <linux/kprobes.h> > #include <linux/ptrace.h> > -#include <linux/spinlock.h> > #include <linux/preempt.h> > #include <asm/cacheflush.h> > #include <asm/kdebug.h> > @@ -125,6 +124,7 @@ static inline void set_current_kprobe(st > kcb->kprobe_saved_msr = regs->msr; > } > > +/* Called with kretprobe_lock held */ > void __kprobes arch_prepare_kretprobe(struct kretprobe *rp, > struct pt_regs *regs) > { > @@ -152,8 +152,6 @@ static inline int kprobe_handler(struct > > /* Check we're not actually recursing */ > if (kprobe_running()) { > - /* We *are* holding lock here, so this is safe. > - Disarm the probe we just hit, and ignore it. */ > p = get_kprobe(addr); > if (p) { > kprobe_opcode_t insn = *p->ainsn.insn; > @@ -161,7 +159,6 @@ static inline int kprobe_handler(struct > is_trap(insn)) { > regs->msr &= ~MSR_SE; > regs->msr |= kcb->kprobe_saved_msr; > - unlock_kprobes(); > goto no_kprobe; > } > /* We have reentered the kprobe_handler(), since > @@ -183,14 +180,11 @@ static inline int kprobe_handler(struct > goto ss_probe; > } > } > - /* If it's not ours, can't be delete race, (we hold lock). */ > goto no_kprobe; > } > > - lock_kprobes(); > p = get_kprobe(addr); > if (!p) { > - unlock_kprobes(); > if (*addr != BREAKPOINT_INSTRUCTION) { > /* > * PowerPC has multiple variants of the "trap" > @@ -254,9 +248,10 @@ int __kprobes trampoline_probe_handler(s > struct kretprobe_instance *ri = NULL; > struct hlist_head *head; > struct hlist_node *node, *tmp; > - unsigned long orig_ret_address = 0; > + unsigned long flags, orig_ret_address = 0; > unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline; > > + spin_lock_irqsave(&kretprobe_lock, flags); > head = kretprobe_inst_table_head(current); > > /* > @@ -296,7 +291,7 @@ int __kprobes trampoline_probe_handler(s > regs->nip = orig_ret_address; > > reset_current_kprobe(); > - unlock_kprobes(); > + spin_unlock_irqrestore(&kretprobe_lock, flags); > preempt_enable_no_resched(); > > /* > @@ -348,7 +343,6 @@ static inline int post_kprobe_handler(st > goto out; > } > reset_current_kprobe(); > - unlock_kprobes(); > out: > preempt_enable_no_resched(); > > @@ -363,7 +357,6 @@ out: > return 1; > } > > -/* Interrupts disabled, kprobe_lock held. */ > static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr) > { > struct kprobe *cur = kprobe_running(); > @@ -378,7 +371,6 @@ static inline int kprobe_fault_handler(s > regs->msr |= kcb->kprobe_saved_msr; > > reset_current_kprobe(); > - unlock_kprobes(); > preempt_enable_no_resched(); > } > return 0; > @@ -393,11 +385,7 @@ int __kprobes kprobe_exceptions_notify(s > struct die_args *args = (struct die_args *)data; > int ret = NOTIFY_DONE; > > - /* > - * Interrupts are not disabled here. We need to disable > - * preemption, because kprobe_running() uses smp_processor_id(). > - */ > - preempt_disable(); > + rcu_read_lock();
And here...
> switch (val) { > case DIE_BPT: > if (kprobe_handler(args->regs)) > @@ -416,7 +404,7 @@ int __kprobes kprobe_exceptions_notify(s > default: > break; > } > - preempt_enable_no_resched(); > + rcu_read_unlock(); > return ret; > } > > Index: linux-2.6.14-rc3/arch/sparc64/kernel/kprobes.c > =================================================================== > --- linux-2.6.14-rc3.orig/arch/sparc64/kernel/kprobes.c 2005-10-05 16:08:15.000000000 -0400 > +++ linux-2.6.14-rc3/arch/sparc64/kernel/kprobes.c 2005-10-05 16:08:48.000000000 -0400 > @@ -116,15 +116,11 @@ static int __kprobes kprobe_handler(stru > struct kprobe_ctlblk *kcb = get_kprobe_ctlblk(); > > if (kprobe_running()) { > - /* We *are* holding lock here, so this is safe. > - * Disarm the probe we just hit, and ignore it. > - */ > p = get_kprobe(addr); > if (p) { > if (kcb->kprobe_status == KPROBE_HIT_SS) { > regs->tstate = ((regs->tstate & ~TSTATE_PIL) | > kcb->kprobe_orig_tstate_pil); > - unlock_kprobes(); > goto no_kprobe; > } > /* We have reentered the kprobe_handler(), since > @@ -144,14 +140,11 @@ static int __kprobes kprobe_handler(stru > if (p->break_handler && p->break_handler(p, regs)) > goto ss_probe; > } > - /* If it's not ours, can't be delete race, (we hold lock). */ > goto no_kprobe; > } > > - lock_kprobes(); > p = get_kprobe(addr); > if (!p) { > - unlock_kprobes(); > if (*(u32 *)addr != BREAKPOINT_INSTRUCTION) { > /* > * The breakpoint instruction was removed right > @@ -296,14 +289,12 @@ static inline int post_kprobe_handler(st > goto out; > } > reset_current_kprobe(); > - unlock_kprobes(); > out: > preempt_enable_no_resched(); > > return 1; > } > > -/* Interrupts disabled, kprobe_lock held. */ > static inline int kprobe_fault_handler(struct pt_regs *regs, int trapnr) > { > struct kprobe *cur = kprobe_running(); > @@ -316,7 +307,6 @@ static inline int kprobe_fault_handler(s > resume_execution(cur, regs, kcb); > > reset_current_kprobe(); > - unlock_kprobes(); > preempt_enable_no_resched(); > } > return 0; > @@ -331,7 +321,7 @@ int __kprobes kprobe_exceptions_notify(s > struct die_args *args = (struct die_args *)data; > int ret = NOTIFY_DONE; > > - preempt_disable(); > + rcu_read_lock();
As well as here...
> switch (val) { > case DIE_DEBUG: > if (kprobe_handler(args->regs)) > @@ -350,7 +340,7 @@ int __kprobes kprobe_exceptions_notify(s > default: > break; > } > - preempt_enable(); > + rcu_read_unlock(); > return ret; > } > > Index: linux-2.6.14-rc3/arch/x86_64/kernel/kprobes.c > =================================================================== > --- linux-2.6.14-rc3.orig/arch/x86_64/kernel/kprobes.c 2005-10-05 16:08:33.000000000 -0400 > +++ linux-2.6.14-rc3/arch/x86_64/kernel/kprobes.c 2005-10-05 16:08:48.000000000 -0400 > @@ -34,7 +34,6 @@ > #include <linux/config.h> > #include <linux/kprobes.h> > #include <linux/ptrace.h> > -#include <linux/spinlock.h> > #include <linux/string.h> > #include <linux/slab.h> > #include <linux/preempt.h> > @@ -266,6 +265,7 @@ static void __kprobes prepare_singlestep > regs->rip = (unsigned long)p->ainsn.insn; > } > > +/* Called with kretprobe_lock held */ > void __kprobes arch_prepare_kretprobe(struct kretprobe *rp, > struct pt_regs *regs) > { > @@ -299,15 +299,12 @@ int __kprobes kprobe_handler(struct pt_r > > /* Check we're not actually recursing */ > if (kprobe_running()) { > - /* We *are* holding lock here, so this is safe. > - Disarm the probe we just hit, and ignore it. */ > p = get_kprobe(addr); > if (p) { > if (kcb->kprobe_status == KPROBE_HIT_SS && > *p->ainsn.insn == BREAKPOINT_INSTRUCTION) { > regs->eflags &= ~TF_MASK; > regs->eflags |= kcb->kprobe_saved_rflags; > - unlock_kprobes(); > goto no_kprobe; > } else if (kcb->kprobe_status == KPROBE_HIT_SSDONE) { > /* TODO: Provide re-entrancy from > @@ -340,14 +337,11 @@ int __kprobes kprobe_handler(struct pt_r > goto ss_probe; > } > } > - /* If it's not ours, can't be delete race, (we hold lock). */ > goto no_kprobe; > } > > - lock_kprobes(); > p = get_kprobe(addr); > if (!p) { > - unlock_kprobes(); > if (*addr != BREAKPOINT_INSTRUCTION) { > /* > * The breakpoint instruction was removed right > @@ -406,9 +400,10 @@ int __kprobes trampoline_probe_handler(s > struct kretprobe_instance *ri = NULL; > struct hlist_head *head; > struct hlist_node *node, *tmp; > - unsigned long orig_ret_address = 0; > + unsigned long flags, orig_ret_address = 0; > unsigned long trampoline_address =(unsigned long)&kretprobe_trampoline; > > + spin_lock_irqsave(&kretprobe_lock, flags); > head = kretprobe_inst_table_head(current); > > /* > @@ -448,7 +443,7 @@ int __kprobes trampoline_probe_handler(s > regs->rip = orig_ret_address; > > reset_current_kprobe(); > - unlock_kprobes(); > + spin_unlock_irqrestore(&kretprobe_lock, flags); > preempt_enable_no_resched(); > > /* > @@ -536,10 +531,6 @@ static void __kprobes resume_execution(s > } > } > > -/* > - * Interrupts are disabled on entry as trap1 is an interrupt gate and they > - * remain disabled thoroughout this function. And we hold kprobe lock. > - */ > int __kprobes post_kprobe_handler(struct pt_regs *regs) > { > struct kprobe *cur = kprobe_running(); > @@ -560,8 +551,6 @@ int __kprobes post_kprobe_handler(struct > if (kcb->kprobe_status == KPROBE_REENTER) { > restore_previous_kprobe(kcb); > goto out; > - } else { > - unlock_kprobes(); > } > reset_current_kprobe(); > out: > @@ -578,7 +567,6 @@ out: > return 1; > } > > -/* Interrupts disabled, kprobe_lock held. */ > int __kprobes kprobe_fault_handler(struct pt_regs *regs, int trapnr) > { > struct kprobe *cur = kprobe_running(); > @@ -592,7 +580,6 @@ int __kprobes kprobe_fault_handler(struc > regs->eflags |= kcb->kprobe_old_rflags; > > reset_current_kprobe(); > - unlock_kprobes(); > preempt_enable_no_resched(); > } > return 0; > @@ -607,7 +594,7 @@ int __kprobes kprobe_exceptions_notify(s > struct die_args *args = (struct die_args *)data; > int ret = NOTIFY_DONE; > > - preempt_disable(); > + rcu_read_lock();
As well as here yet again...
> switch (val) { > case DIE_INT3: > if (kprobe_handler(args->regs)) > @@ -626,7 +613,7 @@ int __kprobes kprobe_exceptions_notify(s > default: > break; > } > - preempt_enable(); > + rcu_read_unlock(); > return ret; > } > > - > 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/ > > - 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/
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