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kprobes: kretprobes simplifications
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 - consolidate duplicate code in all arch_prepare_kretprobe instances
   into common code
 - replace various odd helpers that use hlist_for_each_entry to get
   the first elemenet of a list with either a hlist_for_each_entry_save
   or an opencoded access to the first element in the caller
 - inline add_rp_inst into it's only remaining caller
 - use kretprobe_inst_table_head instead of opencoding it

Signed-off-by: Christoph Hellwig <hch@lst.de>
Cc: Prasanna S Panchamukhi <prasanna@in.ibm.com>
Acked-by: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Christoph Hellwig authored and Linus Torvalds committed May 8, 2007
1 parent 6f716ac commit 4c4308c
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Showing 7 changed files with 44 additions and 114 deletions.
17 changes: 4 additions & 13 deletions arch/i386/kernel/kprobes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -226,24 +226,15 @@ static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
unsigned long *sara = (unsigned long *)&regs->esp;

struct kretprobe_instance *ri;
ri->ret_addr = (kprobe_opcode_t *) *sara;

if ((ri = get_free_rp_inst(rp)) != NULL) {
ri->rp = rp;
ri->task = current;
ri->ret_addr = (kprobe_opcode_t *) *sara;

/* Replace the return addr with trampoline addr */
*sara = (unsigned long) &kretprobe_trampoline;
add_rp_inst(ri);
} else {
rp->nmissed++;
}
/* Replace the return addr with trampoline addr */
*sara = (unsigned long) &kretprobe_trampoline;
}

/*
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18 changes: 4 additions & 14 deletions arch/ia64/kernel/kprobes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -465,23 +465,13 @@ int __kprobes trampoline_probe_handler(struct kprobe *p, struct pt_regs *regs)
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
struct kretprobe_instance *ri;
ri->ret_addr = (kprobe_opcode_t *)regs->b0;

if ((ri = get_free_rp_inst(rp)) != NULL) {
ri->rp = rp;
ri->task = current;
ri->ret_addr = (kprobe_opcode_t *)regs->b0;

/* Replace the return addr with trampoline addr */
regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;

add_rp_inst(ri);
} else {
rp->nmissed++;
}
/* Replace the return addr with trampoline addr */
regs->b0 = ((struct fnptr *)kretprobe_trampoline)->ip;
}

int __kprobes arch_prepare_kprobe(struct kprobe *p)
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19 changes: 5 additions & 14 deletions arch/powerpc/kernel/kprobes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -126,22 +126,13 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
struct kretprobe_instance *ri;

if ((ri = get_free_rp_inst(rp)) != NULL) {
ri->rp = rp;
ri->task = current;
ri->ret_addr = (kprobe_opcode_t *)regs->link;

/* Replace the return addr with trampoline addr */
regs->link = (unsigned long)kretprobe_trampoline;
add_rp_inst(ri);
} else {
rp->nmissed++;
}
ri->ret_addr = (kprobe_opcode_t *)regs->link;

/* Replace the return addr with trampoline addr */
regs->link = (unsigned long)kretprobe_trampoline;
}

static int __kprobes kprobe_handler(struct pt_regs *regs)
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18 changes: 4 additions & 14 deletions arch/s390/kernel/kprobes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -271,23 +271,13 @@ static void __kprobes set_current_kprobe(struct kprobe *p, struct pt_regs *regs,
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
struct kretprobe_instance *ri;
ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];

if ((ri = get_free_rp_inst(rp)) != NULL) {
ri->rp = rp;
ri->task = current;
ri->ret_addr = (kprobe_opcode_t *) regs->gprs[14];

/* Replace the return addr with trampoline addr */
regs->gprs[14] = (unsigned long)&kretprobe_trampoline;

add_rp_inst(ri);
} else {
rp->nmissed++;
}
/* Replace the return addr with trampoline addr */
regs->gprs[14] = (unsigned long)&kretprobe_trampoline;
}

static int __kprobes kprobe_handler(struct pt_regs *regs)
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17 changes: 4 additions & 13 deletions arch/x86_64/kernel/kprobes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -266,23 +266,14 @@ static void __kprobes prepare_singlestep(struct kprobe *p, struct pt_regs *regs)
}

/* Called with kretprobe_lock held */
void __kprobes arch_prepare_kretprobe(struct kretprobe *rp,
void __kprobes arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs)
{
unsigned long *sara = (unsigned long *)regs->rsp;
struct kretprobe_instance *ri;

if ((ri = get_free_rp_inst(rp)) != NULL) {
ri->rp = rp;
ri->task = current;
ri->ret_addr = (kprobe_opcode_t *) *sara;

/* Replace the return addr with trampoline addr */
*sara = (unsigned long) &kretprobe_trampoline;
add_rp_inst(ri);
} else {
rp->nmissed++;
}
ri->ret_addr = (kprobe_opcode_t *) *sara;
/* Replace the return addr with trampoline addr */
*sara = (unsigned long) &kretprobe_trampoline;
}

int __kprobes kprobe_handler(struct pt_regs *regs)
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5 changes: 2 additions & 3 deletions include/linux/kprobes.h
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Original file line number Diff line number Diff line change
Expand Up @@ -123,7 +123,8 @@ DECLARE_PER_CPU(struct kprobe *, current_kprobe);
DECLARE_PER_CPU(struct kprobe_ctlblk, kprobe_ctlblk);

#ifdef ARCH_SUPPORTS_KRETPROBES
extern void arch_prepare_kretprobe(struct kretprobe *rp, struct pt_regs *regs);
extern void arch_prepare_kretprobe(struct kretprobe_instance *ri,
struct pt_regs *regs);
#else /* ARCH_SUPPORTS_KRETPROBES */
static inline void arch_prepare_kretprobe(struct kretprobe *rp,
struct pt_regs *regs)
Expand Down Expand Up @@ -209,8 +210,6 @@ void jprobe_return(void);
int register_kretprobe(struct kretprobe *rp);
void unregister_kretprobe(struct kretprobe *rp);

struct kretprobe_instance *get_free_rp_inst(struct kretprobe *rp);
void add_rp_inst(struct kretprobe_instance *ri);
void kprobe_flush_task(struct task_struct *tk);
void recycle_rp_inst(struct kretprobe_instance *ri, struct hlist_head *head);
#else /* CONFIG_KPROBES */
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64 changes: 21 additions & 43 deletions kernel/kprobes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -357,46 +357,6 @@ void __kprobes kprobes_inc_nmissed_count(struct kprobe *p)
return;
}

/* Called with kretprobe_lock held */
struct kretprobe_instance __kprobes *get_free_rp_inst(struct kretprobe *rp)
{
struct hlist_node *node;
struct kretprobe_instance *ri;
hlist_for_each_entry(ri, node, &rp->free_instances, uflist)
return ri;
return NULL;
}

/* Called with kretprobe_lock held */
static struct kretprobe_instance __kprobes *get_used_rp_inst(struct kretprobe
*rp)
{
struct hlist_node *node;
struct kretprobe_instance *ri;
hlist_for_each_entry(ri, node, &rp->used_instances, uflist)
return ri;
return NULL;
}

/* Called with kretprobe_lock held */
void __kprobes add_rp_inst(struct kretprobe_instance *ri)
{
/*
* Remove rp inst off the free list -
* Add it back when probed function returns
*/
hlist_del(&ri->uflist);

/* Add rp inst onto table */
INIT_HLIST_NODE(&ri->hlist);
hlist_add_head(&ri->hlist,
&kretprobe_inst_table[hash_ptr(ri->task, KPROBE_HASH_BITS)]);

/* Also add this rp inst to the used list. */
INIT_HLIST_NODE(&ri->uflist);
hlist_add_head(&ri->uflist, &ri->rp->used_instances);
}

/* Called with kretprobe_lock held */
void __kprobes recycle_rp_inst(struct kretprobe_instance *ri,
struct hlist_head *head)
Expand Down Expand Up @@ -450,7 +410,9 @@ void __kprobes kprobe_flush_task(struct task_struct *tk)
static inline void free_rp_inst(struct kretprobe *rp)
{
struct kretprobe_instance *ri;
while ((ri = get_free_rp_inst(rp)) != NULL) {
struct hlist_node *pos, *next;

hlist_for_each_entry_safe(ri, pos, next, &rp->free_instances, uflist) {
hlist_del(&ri->uflist);
kfree(ri);
}
Expand Down Expand Up @@ -732,7 +694,21 @@ static int __kprobes pre_handler_kretprobe(struct kprobe *p,

/*TODO: consider to only swap the RA after the last pre_handler fired */
spin_lock_irqsave(&kretprobe_lock, flags);
arch_prepare_kretprobe(rp, regs);
if (!hlist_empty(&rp->free_instances)) {
struct kretprobe_instance *ri;

ri = hlist_entry(rp->free_instances.first,
struct kretprobe_instance, uflist);
ri->rp = rp;
ri->task = current;
arch_prepare_kretprobe(ri, regs);

/* XXX(hch): why is there no hlist_move_head? */
hlist_del(&ri->uflist);
hlist_add_head(&ri->uflist, &ri->rp->used_instances);
hlist_add_head(&ri->hlist, kretprobe_inst_table_head(ri->task));
} else
rp->nmissed++;
spin_unlock_irqrestore(&kretprobe_lock, flags);
return 0;
}
Expand Down Expand Up @@ -795,11 +771,13 @@ void __kprobes unregister_kretprobe(struct kretprobe *rp)
{
unsigned long flags;
struct kretprobe_instance *ri;
struct hlist_node *pos, *next;

unregister_kprobe(&rp->kp);

/* No race here */
spin_lock_irqsave(&kretprobe_lock, flags);
while ((ri = get_used_rp_inst(rp)) != NULL) {
hlist_for_each_entry_safe(ri, pos, next, &rp->used_instances, uflist) {
ri->rp = NULL;
hlist_del(&ri->uflist);
}
Expand Down

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