From: Ananth N Mavinakayanahalli In certain cases like when the real return address can't be found or when the number of tracked calls to a kretprobed function is less than the number of returns, we may not be able to find the correct return address after processing a kretprobe. Currently we just do a BUG_ON, but no information is provided about the actual failing kretprobe. Print out details of the kretprobe before calling BUG(). Signed-off-by: Ananth N Mavinakayanahalli Cc: Prasanna S Panchamukhi Cc: Jim Keniston Cc: Anil S Keshavamurthy Cc: Maneesh Soni Signed-off-by: Andrew Morton --- arch/i386/kernel/kprobes.c | 3 +-- arch/ia64/kernel/kprobes.c | 3 ++- arch/powerpc/kernel/kprobes.c | 2 +- arch/x86_64/kernel/kprobes.c | 2 +- include/linux/kprobes.h | 10 ++++++++++ 5 files changed, 15 insertions(+), 5 deletions(-) diff -puN arch/i386/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure arch/i386/kernel/kprobes.c --- a/arch/i386/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure +++ a/arch/i386/kernel/kprobes.c @@ -449,8 +449,7 @@ fastcall void *__kprobes trampoline_hand break; } - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); - + kretprobe_assert(ri, orig_ret_address, trampoline_address); spin_unlock_irqrestore(&kretprobe_lock, flags); hlist_for_each_entry_safe(ri, node, tmp, &empty_rp, hlist) { diff -puN arch/ia64/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure arch/ia64/kernel/kprobes.c --- a/arch/ia64/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure +++ a/arch/ia64/kernel/kprobes.c @@ -444,7 +444,8 @@ int __kprobes trampoline_probe_handler(s break; } - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); + kretprobe_assert(ri, orig_ret_address, trampoline_address); + regs->cr_iip = orig_ret_address; reset_current_kprobe(); diff -puN arch/powerpc/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure arch/powerpc/kernel/kprobes.c --- a/arch/powerpc/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure +++ a/arch/powerpc/kernel/kprobes.c @@ -336,7 +336,7 @@ int __kprobes trampoline_probe_handler(s break; } - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); + kretprobe_assert(ri, orig_ret_address, trampoline_address); regs->nip = orig_ret_address; reset_current_kprobe(); diff -puN arch/x86_64/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure arch/x86_64/kernel/kprobes.c --- a/arch/x86_64/kernel/kprobes.c~kprobes-print-details-of-kretprobe-on-assertion-failure +++ a/arch/x86_64/kernel/kprobes.c @@ -447,7 +447,7 @@ int __kprobes trampoline_probe_handler(s break; } - BUG_ON(!orig_ret_address || (orig_ret_address == trampoline_address)); + kretprobe_assert(ri, orig_ret_address, trampoline_address); regs->rip = orig_ret_address; reset_current_kprobe(); diff -puN include/linux/kprobes.h~kprobes-print-details-of-kretprobe-on-assertion-failure include/linux/kprobes.h --- a/include/linux/kprobes.h~kprobes-print-details-of-kretprobe-on-assertion-failure +++ a/include/linux/kprobes.h @@ -157,6 +157,16 @@ struct kretprobe_instance { struct task_struct *task; }; +static inline void kretprobe_assert(struct kretprobe_instance *ri, + unsigned long orig_ret_address, unsigned long trampoline_address) +{ + if (!orig_ret_address || (orig_ret_address == trampoline_address)) { + printk("kretprobe BUG!: Processing kretprobe %p @ %p\n", + ri->rp, ri->rp->kp.addr); + BUG(); + } +} + extern spinlock_t kretprobe_lock; extern struct mutex kprobe_mutex; extern int arch_prepare_kprobe(struct kprobe *p); _