From 26172a25aec6434f78a1ac21d5587dc8192e6ba6 Mon Sep 17 00:00:00 2001
From: Patrick Doyle <pdoyle@irobot.com>
Date: Thu, 20 Feb 2020 17:03:30 -0500
Subject: [PATCH] Teach dynlink.c about DT_MIPS_RLD_MAP_REL
Record the address of the debug structure in a location indicated by
DT_MIPS_RLD_MAP_REL so that debuggers can properly debug core files with
dynamic libraries.
See https://binutils.sourceware.narkive.com/aTb1ofXN/patch-mips-support-shared-library-debug-with-mips-pie
for the definition of DT_MIPS_RLD_MAP_REL.
---
ldso/dynlink.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index 6325d8eb..842e7b34 100644
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -1866,6 +1866,23 @@ _Noreturn void __dls3(size_t *sp)
size_t *ptr = (size_t *) app.dynv[i+1];
*ptr = (size_t)&debug;
}
+ /* According to
+ * https://binutils.sourceware.narkive.com/aTb1ofXN/patch-mips-support-shared-library-debug-with-mips-pie
+ * The definition of DT_MIPS_RLD_MAP_REL is:
+ *
+ * This member is used by debugging. It contains a relative offset from the tag's runtime
+ * location of a 32-bit word in the .data section which is supplied by the compilation
+ * environment. The word's contents are not specified and programs using this value are not
+ * ABI - compliant.
+ *
+ * We need to supply the address of the `debug` structure, relative to the address of the
+ * DT_MIPS_RLD_MAP_REL tag, in order for gdb to successfully load the share libraries
+ * referenced by a core file.
+ */
+ if (app.dynv[i]==DT_MIPS_RLD_MAP_REL) {
+ void **ptr = (void **)((char *)&app.dynv[i] + (unsigned)app.dynv[i+1]);
+ *ptr = &debug;
+ }
}
/* This must be done before final relocations, since it calls
--
2.24.1