From: Josh Stone <jistone@redhat.com>
Date: Wed, 7 Nov 2012 19:41:16 +0000 (-0800)
Subject: stapdyn: Workaround for an i686 Dyninst bug in argument passing
X-Git-Tag: release-2.1~301
X-Git-Url: https://sourceware.org/git/?a=commitdiff_plain;h=2f29445de5deaa99bd319d0a7ac649ed6bfcac2f;p=systemtap.git

stapdyn: Workaround for an i686 Dyninst bug in argument passing

Dyninst appears to be filling only 32-bits for the index to
enter_dyninst_uprobe_regs, which makes the following arguments shift
badly too.  This is reported upstream, but we can detect and work around
it ourselves too.
---

diff --git a/runtime/dyninst/uprobes.c b/runtime/dyninst/uprobes.c
index 70ace0ddb..723600967 100644
--- a/runtime/dyninst/uprobes.c
+++ b/runtime/dyninst/uprobes.c
@@ -74,6 +74,16 @@ int enter_dyninst_uprobe_regs(uint64_t index, unsigned long nregs, ...)
 	va_list varegs;
 	va_start(varegs, nregs);
 
+#ifdef __i386__
+	// XXX Dyninst currently has a bug where it's only passing a 32-bit
+	// index, which means nregs gets stuffed into the upper bits of index,
+	// and the varegs are all off by one.  Hacking it into shape for now...
+	if (index > UINT32_MAX) {
+		SET_REG_IP((&regs), nregs);
+                nregs = index >> 32;
+                index &= UINT32_MAX;
+        } else
+#endif
 	if (nregs > 0)
 		SET_REG_IP((&regs), va_arg(varegs, unsigned long));