Messages in this thread | | | Subject | Re: [PATCH v14 7/7] ARM: kprobes: enable OPTPROBES for ARM 32 | From | "Jon Medhurst (Tixy)" <> | Date | Mon, 08 Dec 2014 13:22:14 +0000 |
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On Mon, 2014-12-08 at 20:31 +0800, Wang Nan wrote: > On 2014/12/8 20:06, Wang Nan wrote: > > On 2014/12/8 19:50, Jon Medhurst (Tixy) wrote: > >> On Mon, 2014-12-08 at 19:15 +0800, Wang Nan wrote: > >>> On 2014/12/8 19:04, Jon Medhurst (Tixy) wrote: > >>>> On Mon, 2014-12-08 at 14:28 +0800, Wang Nan wrote: > [...] > >> > >> so another CPU could find and delete next before this one has finished > >> doing so. Would the list end up in a consistent state where no loops > >> develop and no probes are missed? I don't know the answer and a full > >> analysis would be complicated, but my gut feeling is that if a cpu can > >> observe the links in the list in an inconsistent state then only bad > >> things can result. > >> > > > > I see the problem. > > > > I'm thinking about making core.c and opt-arm.c to share stop_machine() code. > > stop_machine() is required when removing breakpoint, so I'd like to define > > a "remove_breakpoint" function in core.c and make opt-arm.c to call it. > > Do you think it is a good idea? > > > > > > What I mean is something like this:
Yes, that should work, though as remove_breakpoint is a globally visible symbol, I suggest a less generic name for it, perhaps remove_kprobe_breakpoint ?
-- Tixy
> diff --git a/arch/arm/probes/kprobes/core.c b/arch/arm/probes/kprobes/core.c > index 3a58db4..efd8ab1 100644 > --- a/arch/arm/probes/kprobes/core.c > +++ b/arch/arm/probes/kprobes/core.c > @@ -163,19 +163,31 @@ void __kprobes arch_arm_kprobe(struct kprobe *p) > * memory. It is also needed to atomically set the two half-words of a 32-bit > * Thumb breakpoint. > */ > -int __kprobes __arch_disarm_kprobe(void *p) > -{ > - struct kprobe *kp = p; > - void *addr = (void *)((uintptr_t)kp->addr & ~1); > - > - __patch_text(addr, kp->opcode); > +struct patch { > + void *addr; > + unsigned int insn; > +}; > > +static int __remove_breakpoint(void *data) > +{ > + struct patch *p = data; > + __patch_text(p->addr, p->insn); > return 0; > } > > +void __kprobes remove_breakpoint(void *addr, unsigned int insn) > +{ > + struct patch p = { > + .addr = addr, > + .insn = insn, > + }; > + stop_machine(__remove_breakpoint, &p, cpu_online_mask); > +} > + > void __kprobes arch_disarm_kprobe(struct kprobe *p) > { > - stop_machine(__arch_disarm_kprobe, p, cpu_online_mask); > + remove_breakpoint((void *)((uintptr_t)p->addr & ~1), > + p->opcode); > } > > void __kprobes arch_remove_kprobe(struct kprobe *p) > diff --git a/arch/arm/probes/kprobes/core.h b/arch/arm/probes/kprobes/core.h > index f88c79f..7b7c334 100644 > --- a/arch/arm/probes/kprobes/core.h > +++ b/arch/arm/probes/kprobes/core.h > @@ -30,6 +30,8 @@ > #define KPROBE_THUMB16_BREAKPOINT_INSTRUCTION 0xde18 > #define KPROBE_THUMB32_BREAKPOINT_INSTRUCTION 0xf7f0a018 > > +extern void remove_breakpoint(void *addr, unsigned int insn); > + > enum probes_insn __kprobes > kprobe_decode_ldmstm(kprobe_opcode_t insn, struct arch_probes_insn *asi, > const struct decode_header *h); > diff --git a/arch/arm/probes/kprobes/opt-arm.c b/arch/arm/probes/kprobes/opt-arm.c > index afbfeef..a1a1882 100644 > --- a/arch/arm/probes/kprobes/opt-arm.c > +++ b/arch/arm/probes/kprobes/opt-arm.c > @@ -28,8 +28,9 @@ > #include <asm/insn.h> > /* for patch_text */ > #include <asm/patch.h> > -/* for stop_machine */ > -#include <linux/stop_machine.h> > + > +#include "core.h" > + > /* > * NOTE: the first sub and add instruction will be modified according > * to the stack cost of the instruction. > @@ -245,13 +246,8 @@ int arch_prepare_optimized_kprobe(struct optimized_kprobe *op, struct kprobe *or > return 0; > } > > -/* > - * Similar to __arch_disarm_kprobe, operations which removing > - * breakpoints must be wrapped by stop_machine to avoid racing. > - */ > -static __kprobes int __arch_optimize_kprobes(void *p) > +void __kprobes arch_optimize_kprobes(struct list_head *oplist) > { > - struct list_head *oplist = p; > struct optimized_kprobe *op, *tmp; > > list_for_each_entry_safe(op, tmp, oplist, list) { > @@ -277,16 +273,15 @@ static __kprobes int __arch_optimize_kprobes(void *p) > op->optinsn.copied_insn[0]) & 0xf0000000) | > (insn & 0x0fffffff); > > - patch_text(op->kp.addr, insn); > + /* > + * Similar to __arch_disarm_kprobe, operations which > + * removing breakpoints must be wrapped by stop_machine > + * to avoid racing. > + */ > + remove_breakpoint(op->kp.addr, insn); > > list_del_init(&op->list); > } > - return 0; > -} > - > -void arch_optimize_kprobes(struct list_head *oplist) > -{ > - stop_machine(__arch_optimize_kprobes, oplist, cpu_online_mask); > } > > void arch_unoptimize_kprobe(struct optimized_kprobe *op)
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