[PATCH 2/9] add qemu-modinfo utility

[Gerd Hoffmann <kraxel@redhat.com>]

For now only dump metadata.

TODO:
 * store in some file format (json?).
 * make qemu parse it, replace hard-coded lists in util/module.c
 * fix windows (seems to not have glob).
 * do we need non-elf support?

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
---
 qemu-modinfo.c | 182 +++++++++++++++++++++++++++++++++++++++++++++++++
 meson.build    |   3 +
 2 files changed, 185 insertions(+)
 create mode 100644 qemu-modinfo.c

diff --git a/qemu-modinfo.c b/qemu-modinfo.c
new file mode 100644
index 000000000000..ecd5f6c3adf2
--- /dev/null
+++ b/qemu-modinfo.c
@@ -0,0 +1,182 @@
+/*
+ * QEMU module parser
+ *
+ * read modules, find modinfo section, parse & store metadata.
+ *
+ * Copyright Red Hat, Inc. 2021
+ *
+ * Authors:
+ *     Gerd Hoffmann <kraxel@redhat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+#include "qemu/osdep.h"
+#include "elf.h"
+#include <glob.h>
+
+#define Elf_Ehdr Elf64_Ehdr
+#define Elf_Shdr Elf64_Shdr
+#define ELFCLASS ELFCLASS64
+
+static const char *moddir = CONFIG_QEMU_MODDIR;
+static const char *dsosuf = CONFIG_HOST_DSOSUF;
+
+static void modinfo(const char *module, char *info, size_t size)
+{
+    size_t pos = 0, len;
+
+    fprintf(stderr, "%s\n", module);
+    do {
+        fprintf(stderr, "  -> %s\n", info + pos);
+        len = strlen(info + pos) + 1;
+        pos += len;
+    } while (pos < size);
+}
+
+static void elf_read_section_hdr(FILE *fp, Elf_Ehdr *ehdr,
+                                 int section, Elf_Shdr *shdr)
+{
+    size_t pos, len;
+    int ret;
+
+    pos = ehdr->e_shoff + section * ehdr->e_shentsize;
+    len = MIN(ehdr->e_shentsize, sizeof(*shdr));
+
+    ret = fseek(fp, pos, SEEK_SET);
+    if (ret != 0) {
+        fprintf(stderr, "seek error\n");
+        exit(1);
+    }
+
+    memset(shdr, 0, sizeof(*shdr));
+    ret = fread(shdr, len, 1, fp);
+    if (ret != 1) {
+        fprintf(stderr, "read error\n");
+        exit(1);
+    }
+}
+
+static void *elf_read_section(FILE *fp, Elf_Ehdr *ehdr,
+                              int section, size_t *size)
+{
+    Elf_Shdr shdr;
+    void *data;
+    int ret;
+
+    elf_read_section_hdr(fp, ehdr, section, &shdr);
+    if (shdr.sh_offset && shdr.sh_size) {
+        ret = fseek(fp, shdr.sh_offset, SEEK_SET);
+        if (ret != 0) {
+            fprintf(stderr, "seek error\n");
+            exit(1);
+        }
+
+        data = g_malloc(shdr.sh_size);
+        ret = fread(data, shdr.sh_size, 1, fp);
+        if (ret != 1) {
+            fprintf(stderr, "read error\n");
+            exit(1);
+        }
+        *size = shdr.sh_size;
+    } else {
+        data = NULL;
+        *size = 0;
+    }
+    return data;
+}
+
+static void elf_parse_module(const char *module)
+{
+    Elf_Ehdr ehdr;
+    Elf_Shdr shdr;
+    FILE *fp;
+    int ret, i;
+    char *str;
+    size_t str_size;
+    char *info;
+    size_t info_size;
+
+    fp = fopen(module, "r");
+    if (NULL == fp) {
+        fprintf(stderr, "open %s: %s\n", module, strerror(errno));
+        exit(1);
+    }
+
+    ret = fread(&ehdr, sizeof(ehdr), 1, fp);
+    if (ret != 1) {
+        fprintf(stderr, "read error (%s)\n", module);
+        exit(1);
+    }
+
+    if (ehdr.e_ident[EI_MAG0] != ELFMAG0 ||
+        ehdr.e_ident[EI_MAG1] != ELFMAG1 ||
+        ehdr.e_ident[EI_MAG2] != ELFMAG2 ||
+        ehdr.e_ident[EI_MAG3] != ELFMAG3) {
+        fprintf(stderr, "not an elf file (%s)\n", module);
+        exit(1);
+    }
+    if (ehdr.e_ident[EI_CLASS] != ELFCLASS64) {
+        fprintf(stderr, "elf class mismatch (%s)\n", module);
+        exit(1);
+    }
+    if (ehdr.e_shoff == 0) {
+        fprintf(stderr, "no section header (%s)\n", module);
+        exit(1);
+    }
+
+    /* read string table */
+    if (ehdr.e_shstrndx == 0) {
+        fprintf(stderr, "no section strings (%s)\n", module);
+        exit(1);
+    }
+    str = elf_read_section(fp, &ehdr, ehdr.e_shstrndx, &str_size);
+    if (NULL == str) {
+        fprintf(stderr, "no section strings (%s)\n", module);
+        exit(1);
+    }
+
+    /* find and read modinfo section */
+    info = NULL;
+    for (i = 0; i < ehdr.e_shnum; i++) {
+        elf_read_section_hdr(fp, &ehdr, i, &shdr);
+        if (!shdr.sh_name) {
+            continue;
+        }
+        if (strcmp(str + shdr.sh_name, ".modinfo") == 0) {
+            info = elf_read_section(fp, &ehdr, i, &info_size);
+        }
+    }
+
+    if (info) {
+        modinfo(module, info, info_size);
+    }
+
+    fclose(fp);
+}
+
+int main(int argc, char **argv)
+{
+    char *pattern;
+    glob_t files;
+    int ret, i;
+
+    if (argc > 1) {
+        moddir = argv[1];
+    }
+
+    pattern = g_strdup_printf("%s/*%s", moddir, dsosuf);
+    ret = glob(pattern, 0, NULL, &files);
+    if (ret != 0) {
+        fprintf(stderr, "glob(%s) failed: %d\n", pattern, ret);
+        exit(1);
+    }
+
+    for (i = 0; i < files.gl_pathc; i++) {
+        elf_parse_module(files.gl_pathv[i]);
+    }
+
+    globfree(&files);
+    g_free(pattern);
+    return 0;
+}
diff --git a/meson.build b/meson.build
index a45f1a844f13..179e92aa7ae1 100644
--- a/meson.build
+++ b/meson.build
@@ -2358,6 +2358,9 @@ if xkbcommon.found()
                            dependencies: [qemuutil, xkbcommon], install: have_tools)
 endif
 
+qemu_modinfo = executable('qemu-modinfo', files('qemu-modinfo.c') + genh,
+                          dependencies: [glib], install: have_tools)
+
 if have_tools
   qemu_img = executable('qemu-img', [files('qemu-img.c'), hxdep],
              dependencies: [authz, block, crypto, io, qom, qemuutil], install: true)
-- 
2.31.1