Commit 7b868e48 authored Jul 21, 2015 by Oleg Nesterov Committed by Ingo Molnar Jul 31, 2015

uprobes/x86: Reimplement arch_uretprobe_is_alive()



Add the x86 specific version of arch_uretprobe_is_alive()
helper. It returns true if the stack frame mangled by
prepare_uretprobe() is still on stack. So if it returns false,
we know that the probed function has already returned.

We add the new return_instance->stack member and change the
generic code to initialize it in prepare_uretprobe, but it
should be equally useful for other architectures.

TODO: this assumes that the probed application can't use
      multiple stacks (say sigaltstack). We will try to improve
      this logic later.

Tested-by: Pratyush Anand <panand@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Acked-by: Anton Arapov <arapov@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20150721134018.GA4766@redhat.com


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 97da8976

arch/x86/kernel/uprobes.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -985,3 +985,8 @@ arch_uretprobe_hijack_return_addr(unsigned long trampoline_vaddr, struct pt_regs

		return -1;
		}

		bool arch_uretprobe_is_alive(struct return_instance ret, struct pt_regs regs)
		{
		return regs->sp <= ret->stack;
		}

include/linux/uprobes.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -95,6 +95,7 @@ struct uprobe_task {
		struct return_instance {
		struct uprobe *uprobe;
		unsigned long func;
		unsigned long stack; /* stack pointer */
		unsigned long orig_ret_vaddr; /* original return address */
		bool chained; /* true, if instance is nested */

kernel/events/uprobes.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1562,6 +1562,7 @@ static void prepare_uretprobe(struct uprobe uprobe, struct pt_regs regs)

		ri->uprobe = get_uprobe(uprobe);
		ri->func = instruction_pointer(regs);
		ri->stack = user_stack_pointer(regs);
		ri->orig_ret_vaddr = orig_ret_vaddr;
		ri->chained = chained;

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