From 7a9011db32b5a24f29e725220d0ba9e970412f47 Mon Sep 17 00:00:00 2001 From: "David A. Long" Date: Fri, 12 Aug 2016 16:24:44 -0400 Subject: [PATCH] Documentation: kprobes: Document jprobes stack copying limitations Some architectures (i.e.: sparc64 and arm64) make reasonable partial stack duplication for jprobes problematic. Document this. Signed-off-by: David A. Long Acked-by: Catalin Marinas Acked-by: Masami Hiramatsu Signed-off-by: Jonathan Corbet --- Documentation/kprobes.txt | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/Documentation/kprobes.txt b/Documentation/kprobes.txt index 1f9b3e2b98ae..1f6d45abfe42 100644 --- a/Documentation/kprobes.txt +++ b/Documentation/kprobes.txt @@ -103,6 +103,16 @@ Note that the probed function's args may be passed on the stack or in registers. The jprobe will work in either case, so long as the handler's prototype matches that of the probed function. +Note that in some architectures (e.g.: arm64 and sparc64) the stack +copy is not done, as the actual location of stacked parameters may be +outside of a reasonable MAX_STACK_SIZE value and because that location +cannot be determined by the jprobes code. In this case the jprobes +user must be careful to make certain the calling signature of the +function does not cause parameters to be passed on the stack (e.g.: +more than eight function arguments, an argument of more than sixteen +bytes, or more than 64 bytes of argument data, depending on +architecture). + 1.3 Return Probes 1.3.1 How Does a Return Probe Work?