From: Ross Lagerwall <ross.lagerwall@citrix.com>
Date: Fri, 6 Nov 2015 12:55:25 +0000 (+0000)
Subject: Implement run-time linking
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=d1c9e3524f8b80cd51aea512c93081ffc2f1a18b;p=livepatch-build-tools.git

Implement run-time linking

Implement run-time linking and link at run-time by default. Still keep
the option to link at compile time.
---

diff --git a/create-diff-object.c b/create-diff-object.c
index fb9ef0b..b542ee9 100644
--- a/create-diff-object.c
+++ b/create-diff-object.c
@@ -1457,7 +1457,7 @@ static struct section *create_section_pair(struct xsplice_elf *kelf,
 
 static void xsplice_create_patches_sections(struct xsplice_elf *kelf,
 					    struct lookup_table *table,
-					    char *hint)
+					    char *hint, int resolve)
 {
 	int nr, index;
 	struct section *sec, *relasec;
@@ -1504,7 +1504,11 @@ static void xsplice_create_patches_sections(struct xsplice_elf *kelf,
 				ERROR("%s too small to patch", sym->name);
 
 			/* add entry in text section */
-			funcs[index].old_addr = result.value;
+			if (resolve)
+				funcs[index].old_addr = result.value;
+			else
+				/* This will be filled in at module load time */
+				funcs[index].old_addr = 0;
 			funcs[index].old_size = result.size;
 			funcs[index].new_addr = 0;
 			funcs[index].new_size = sym->sym.st_size;
@@ -1598,12 +1602,14 @@ static void xsplice_reindex_elements(struct xsplice_elf *kelf)
 struct arguments {
 	char *args[4];
 	int debug;
+	int resolve;
 };
 
 static char args_doc[] = "original.o patched.o kernel-object output.o";
 
 static struct argp_option options[] = {
 	{"debug", 'd', 0, 0, "Show debug output" },
+	{"resolve", 'r', 0, 0, "Resolve to-be-patched function addresses" },
 	{ 0 }
 };
 
@@ -1618,6 +1624,9 @@ static error_t parse_opt (int key, char *arg, struct argp_state *state)
 		case 'd':
 			arguments->debug = 1;
 			break;
+		case 'r':
+			arguments->resolve = 1;
+			break;
 		case ARGP_KEY_ARG:
 			if (state->arg_num >= 4)
 				/* Too many arguments. */
@@ -1648,6 +1657,7 @@ int main(int argc, char *argv[])
 	char *hint = NULL;
 
 	arguments.debug = 0;
+	arguments.resolve = 0;
 	argp_parse (&argp, argc, argv, 0, 0, &arguments);
 	if (arguments.debug)
 		loglevel = DEBUG;
@@ -1763,7 +1773,8 @@ int main(int argc, char *argv[])
 	log_debug("Create strings elements\n");
 	xsplice_create_strings_elements(kelf_out);
 	log_debug("Create patches sections\n");
-	xsplice_create_patches_sections(kelf_out, lookup, hint);
+	xsplice_create_patches_sections(kelf_out, lookup, hint,
+			                arguments.resolve);
 	xsplice_build_strings_section_data(kelf_out);
 
 	/*
diff --git a/xsplice-build b/xsplice-build
index f5495c0..a67ebc0 100755
--- a/xsplice-build
+++ b/xsplice-build
@@ -30,6 +30,7 @@ DEBUG=n
 XEN_DEBUG=n
 SKIP=
 DEPENDS=
+PRELINK=
 XENSYMS=xen-syms
 
 warn() {
@@ -111,7 +112,7 @@ function create_patch()
         mkdir -p "output/$(dirname $i)" || die
         echo "Processing ${i}"
         echo "Run create-diff-object on $i" >> "${OUTPUT}/create-diff-object.log"
-        "${SCRIPTDIR}"/create-diff-object $debugopt "original/$i" "patched/$i" "$XENSYMS" "output/$i" &>> "${OUTPUT}/create-diff-object.log"
+        "${SCRIPTDIR}"/create-diff-object $debugopt $PRELINK "original/$i" "patched/$i" "$XENSYMS" "output/$i" &>> "${OUTPUT}/create-diff-object.log"
         rc="${PIPESTATUS[0]}"
         if [[ $rc = 139 ]]; then
             warn "create-diff-object SIGSEGV"
@@ -143,8 +144,13 @@ function create_patch()
     fi
 
     echo "Creating patch module..."
-    ld -r -o output.o --build-id=sha1 $(find output -type f -name "*.o") || die
-    "${SCRIPTDIR}"/prelink $debugopt output.o "${PATCHNAME}.xsplice" "$XENSYMS" &>> "${OUTPUT}/prelink.log" || die
+    if [ -z "$PRELINK" ]; then
+        ld -r -o "${PATCHNAME}.xsplice" --build-id=sha1 $(find output -type f -name "*.o") || die
+        chmod +x "${PATCHNAME}.xsplice"
+    else
+        ld -r -o output.o --build-id=sha1 $(find output -type f -name "*.o") || die
+        "${SCRIPTDIR}"/prelink $debugopt output.o "${PATCHNAME}.xsplice" "$XENSYMS" &>> "${OUTPUT}/prelink.log" || die
+    fi
 
     objcopy --add-section .xsplice.depends=depends.bin "${PATCHNAME}.xsplice"
     objcopy --set-section-flags .xsplice.depends=alloc,readonly "${PATCHNAME}.xsplice"
@@ -162,9 +168,10 @@ usage() {
     echo "        --xen-debug        Build debug Xen" >&2
     echo "        --xen-syms         Build against a xen-syms" >&2
     echo "        --depends          Required build-id" >&2
+    echo "        --prelink          Prelink" >&2
 }
 
-options=$(getopt -o hs:p:o:j:k:d -l "help,srcdir:patch:output:cpus:,skip:,debug,xen-debug,xen-syms:,depends:" -- "$@") || die "getopt failed"
+options=$(getopt -o hs:p:o:j:k:d -l "help,srcdir:patch:output:cpus:,skip:,debug,xen-debug,xen-syms:,depends:,prelink" -- "$@") || die "getopt failed"
 
 eval set -- "$options"
 
@@ -218,6 +225,10 @@ while [[ $# -gt 0 ]]; do
             DEPENDS="$1"
             shift
             ;;
+        --prelink)
+            PRELINK=--resolve
+            shift
+            ;;
         --)
             shift
             break