4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Masami Hiramatsu mhiramat@kernel.org
[ Upstream commit 06553175f585b52509c7df37d6f4a50aacb7b211 ]
This is arm port of commit 737480a0d525 ("kprobes/x86: Fix the return address of multiple kretprobes").
Fix the return address of subsequent kretprobes when multiple kretprobes are set on the same function.
For example:
# cd /sys/kernel/debug/tracing # echo "r:event1 sys_symlink" > kprobe_events # echo "r:event2 sys_symlink" >> kprobe_events # echo 1 > events/kprobes/enable # ln -s /tmp/foo /tmp/bar
(without this patch)
# cat trace | grep -v ^# ln-82 [000] dn.2 68.446525: event1: (kretprobe_trampoline+0x0/0x18 <- SyS_symlink) ln-82 [000] dn.2 68.447831: event2: (ret_fast_syscall+0x0/0x1c <- SyS_symlink)
(with this patch)
# cat trace | grep -v ^# ln-81 [000] dn.1 39.463469: event1: (ret_fast_syscall+0x0/0x1c <- SyS_symlink) ln-81 [000] dn.1 39.464701: event2: (ret_fast_syscall+0x0/0x1c <- SyS_symlink)
Signed-off-by: Masami Hiramatsu mhiramat@kernel.org Cc: KUMANO Syuhei kumano.prog@gmail.com Signed-off-by: Jon Medhurst tixy@linaro.org Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm/probes/kprobes/core.c | 24 ++++++++++++++++++++++-- 1 file changed, 22 insertions(+), 2 deletions(-)
--- a/arch/arm/probes/kprobes/core.c +++ b/arch/arm/probes/kprobes/core.c @@ -433,6 +433,7 @@ static __used __kprobes void *trampoline struct hlist_node *tmp; unsigned long flags, orig_ret_address = 0; unsigned long trampoline_address = (unsigned long)&kretprobe_trampoline; + kprobe_opcode_t *correct_ret_addr = NULL;
INIT_HLIST_HEAD(&empty_rp); kretprobe_hash_lock(current, &head, &flags); @@ -455,14 +456,34 @@ static __used __kprobes void *trampoline /* another task is sharing our hash bucket */ continue;
+ orig_ret_address = (unsigned long)ri->ret_addr; + + if (orig_ret_address != trampoline_address) + /* + * This is the real return address. Any other + * instances associated with this task are for + * other calls deeper on the call stack + */ + break; + } + + kretprobe_assert(ri, orig_ret_address, trampoline_address); + + correct_ret_addr = ri->ret_addr; + hlist_for_each_entry_safe(ri, tmp, head, hlist) { + if (ri->task != current) + /* another task is sharing our hash bucket */ + continue; + + orig_ret_address = (unsigned long)ri->ret_addr; if (ri->rp && ri->rp->handler) { __this_cpu_write(current_kprobe, &ri->rp->kp); get_kprobe_ctlblk()->kprobe_status = KPROBE_HIT_ACTIVE; + ri->ret_addr = correct_ret_addr; ri->rp->handler(ri, regs); __this_cpu_write(current_kprobe, NULL); }
- orig_ret_address = (unsigned long)ri->ret_addr; recycle_rp_inst(ri, &empty_rp);
if (orig_ret_address != trampoline_address) @@ -474,7 +495,6 @@ static __used __kprobes void *trampoline break; }
- kretprobe_assert(ri, orig_ret_address, trampoline_address); kretprobe_hash_unlock(current, &flags);
hlist_for_each_entry_safe(ri, tmp, &empty_rp, hlist) {