Enhance requires with version information from the build root.

The --libtool-version-fallback option will cause elfdeps to
try to use the version information in the shared object's filename
for shared objects that don't provide versioned symbols. This
additional information allows rpm to track minor-version
dependencies.

Author: gordonmessmer

tools/elfdeps.c

@@ -2,16 +2,21 @@
 
 #include <sys/types.h>
 #include <sys/stat.h>
+#include <sys/wait.h>
 #include <unistd.h>
 #include <stdlib.h>
 #include <fcntl.h>
 #include <errno.h>
 #include <popt.h>
 #include <gelf.h>
 
+#include <link.h>
+#include <dlfcn.h>
+
 #include <rpm/rpmstring.h>
 #include <rpm/argv.h>
 
+int libtool_version_fallback = 0;
 int soname_only = 0;
 int fake_soname = 1;
 int filter_soname = 1;
@@ -33,6 +38,97 @@ typedef struct elfInfo_s {
     ARGV_t provides;
 } elfInfo;
 
+/*
+ * If filename contains ".so" followed by a version number, return
+ * a copy of the version number.
+ */
+static char *getLibtoolVer(const char *filename)
+{
+    const char *so;
+    char dest[PATH_MAX];
+    int destsize = 0;
+    int found_digit = 0, found_dot = 0;
+
+    destsize = readlink(filename, dest, PATH_MAX);
+    if (destsize > 0) {
+	dest[destsize] = 0;
+	filename = dest;
+    }
+    // Start from the end of the string.  Verify that it ends with
+    // numbers and dots, preceded by ".so.".
+    so = filename + strlen(filename);
+    while (so > filename+2) {
+	if (*so == '.') {
+	    found_dot++;
+	    so--;
+	    continue;
+	} else if (strchr("0123456789", *so)) {
+	    found_digit++;
+	    so--;
+	    continue;
+	} else if (strncmp(so-2, ".so.", 4) == 0) {
+	    so+=2;
+	    if (found_digit && found_dot > 1) {
+		return strdup(so);
+	    }
+	    break;
+	} else {
+	    break;
+	}
+    }
+    return NULL;
+}
+
+/*
+ * Rather than re-implement path searching for shared objects, use
+ * dlmopen().  This will still perform initialization and finalization
+ * functions, which isn't necessarily safe, so do that in a separate
+ * process.
+ */
+static char *getLibtoolVerFromShLink(const char *filename)
+{
+    char dest[PATH_MAX];
+    int pipefd[2];
+    pid_t cpid;
+
+    if (pipe(pipefd) == -1) {
+	return NULL;  // Should this be a fatal error instead?
+    }
+    cpid = fork();
+    if (cpid == -1) {
+	return NULL;  // Should this be a fatal error instead?
+    }
+    if (cpid == 0) {
+	void *dl_handle;
+	struct link_map *linkmap;
+	char *version = NULL;
+
+	close(pipefd[0]);
+	dl_handle = dlmopen(LM_ID_NEWLM, filename, RTLD_LAZY);
+	if (dl_handle == NULL) _exit(0);
+	if (dlinfo(dl_handle, RTLD_DI_LINKMAP, &linkmap) != -1) {
+	    version = getLibtoolVer(linkmap->l_name);
+	}
+	(void) write(pipefd[1], version, strlen(version));
+	close(pipefd[1]);
+	free(version);
+	dlclose(dl_handle);
+	_exit(0);
+    } else {
+	ssize_t len;
+	close(pipefd[1]);
+	dest[0] = 0;
+	len = read(pipefd[0], dest, sizeof(dest));
+	if (len > 0) dest[len] = 0;
+	close(pipefd[0]);
+	wait(NULL);
+    }
+    if (strlen(dest) > 0)
+	return strdup(dest);
+    else
+	return NULL;
+}
+
 /*
  * Rough soname sanity filtering: all sane soname's dependencies need to
  * contain ".so", and normal linkable libraries start with "lib",
@@ -95,15 +191,30 @@ static const char *mkmarker(GElf_Ehdr *ehdr)
     return marker;
 }
 
+static int findSonameInDeps(ARGV_t deps, const char *soname)
+{
+    for (ARGV_t dep = deps; *dep; dep++) {
+	if (strncmp(*dep, soname, strlen(soname)) == 0) return 1;
+    }
+    return 0;
+}
+
 static void addDep(ARGV_t *deps,
-		   const char *soname, const char *ver, const char *marker)
+		   const char *soname, const char *ver, const char *marker,
+		   const char *compare_op, const char *fallback_ver)
 {
     char *dep = NULL;
 
     if (skipSoname(soname))
 	return;
 
-    if (ver || marker) {
+    if (compare_op && fallback_ver) {
+	// when versioned symbols aren't available, the libtool version
+	// might be used to generate a minimum dependency version.
+	rasprintf(&dep,
+		  "%s()%s %s %s", soname, marker ? marker : "",
+		  compare_op, fallback_ver);
+    } else if (ver || marker) {
 	rasprintf(&dep,
 		  "%s(%s)%s", soname, ver ? ver : "", marker ? marker : "");
     }
@@ -143,10 +254,10 @@ static void processVerDef(Elf_Scn *scn, GElf_Shdr *shdr, elfInfo *ei)
 		    auxoffset += aux->vda_next;
 		    continue;
 		} else if (soname && !soname_only) {
-		    addDep(&ei->provides, soname, s, ei->marker);
+		    addDep(&ei->provides, soname, s, ei->marker, NULL, NULL);
 		}
 	    }
-		    
+
 	}
     }
     rfree(soname);
@@ -182,7 +293,7 @@ static void processVerNeed(Elf_Scn *scn, GElf_Shdr *shdr, elfInfo *ei)
 		    break;
 
 		if (genRequires(ei) && soname && !soname_only) {
-		    addDep(&ei->requires, soname, s, ei->marker);
+		    addDep(&ei->requires, soname, s, ei->marker, NULL, NULL);
 		}
 		auxoffset += aux->vna_next;
 	    }
@@ -222,8 +333,17 @@ static void processDynamic(Elf_Scn *scn, GElf_Shdr *shdr, elfInfo *ei)
 	    case DT_NEEDED:
 		if (genRequires(ei)) {
 		    s = elf_strptr(ei->elf, shdr->sh_link, dyn->d_un.d_val);
-		    if (s)
-			addDep(&ei->requires, s, NULL, ei->marker);
+		    if (s) {
+			char *libtool_ver = NULL;
+			// If soname matches an item already in the deps, then
+			// it had versioned symbols and doesn't require fallback.
+			if (libtool_version_fallback &&
+			    !findSonameInDeps(ei->requires, s)) {
+			    libtool_ver = getLibtoolVerFromShLink(s);
+			}
+			addDep(&ei->requires, s, NULL, ei->marker, ">=", libtool_ver);
+			free(libtool_ver);
+		    }
 		}
 		break;
 	    }
@@ -322,8 +442,14 @@ static int processFile(const char *fn, int dtype)
 	    const char *bn = strrchr(fn, '/');
 	    ei->soname = rstrdup(bn ? bn + 1 : fn);
 	}
-	if (ei->soname)
-	    addDep(&ei->provides, ei->soname, NULL, ei->marker);
+	if (ei->soname) {
+	    char *libtool_ver = NULL;
+	    if (libtool_version_fallback) {
+		libtool_ver = getLibtoolVer(fn);
+	    }
+	    addDep(&ei->provides, ei->soname, NULL, ei->marker, "=", libtool_ver);
+	    free(libtool_ver);
+	}
     }
 
     /* If requested and present, add dep for interpreter (ie dynamic linker) */
@@ -359,11 +485,12 @@ int main(int argc, char *argv[])
     struct poptOption opts[] = {
 	{ "provides", 'P', POPT_ARG_VAL, &provides, -1, NULL, NULL },
 	{ "requires", 'R', POPT_ARG_VAL, &requires, -1, NULL, NULL },
+	{ "libtool-version-fallback", 0, POPT_ARG_VAL, &libtool_version_fallback, -1, NULL, NULL },
 	{ "soname-only", 0, POPT_ARG_VAL, &soname_only, -1, NULL, NULL },
 	{ "no-fake-soname", 0, POPT_ARG_VAL, &fake_soname, 0, NULL, NULL },
 	{ "no-filter-soname", 0, POPT_ARG_VAL, &filter_soname, 0, NULL, NULL },
 	{ "require-interp", 0, POPT_ARG_VAL, &require_interp, -1, NULL, NULL },
-	POPT_AUTOHELP 
+	POPT_AUTOHELP
 	POPT_TABLEEND
     };