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build-initvm: new files for static binary to register qemu binfmt_misc

Introduces initvm.c, which will be compiled by later to a binary,
$BUILD_DIR/initvm.  initvm will:

    1) mount proc and binfmt_misc and verify correct setup
    2) read qemu-reg from /.build or /usr/lib/build and for each line,
       install binfmt_misc support and verify success
    3) verify existence of /.build/build and run the build script

This functionality obviates the need for $BUILD_DIR/initscript_qemu_vm
and the bash-static and mount-static x86 packages, but does not remove
build's ability to use them.

Signed-off-by: James Perkins <james.perkins@linuxfoundation.org>
  • Loading branch information...
commit aecabd999bc1d30e1d2d27ea40a884f59e71dfe5 1 parent 0215004
James Perkins authored Jan-Simon Möller committed
Showing with 342 additions and 0 deletions.
  1. +329 −0 initvm.c
  2. +13 −0 qemu-reg
View
329 initvm.c
@@ -0,0 +1,329 @@
+/*
+ * NAME
+ * initvm - init for qemu, setup binfmt_misc launch build
+ *
+ * SYNOPSIS
+ * initvm
+ *
+ * DESCRIPTION
+ * This is the kernel init script for virtual machines which will
+ * be running executables for an embedded (non-native)
+ * architecture. It registers binfmt_misc handlers for qemu and
+ * executes the build script, and tests many assumptions.
+ *
+ * FILES
+ * /.build/qemu-reg
+ * text file with lines to stuff into the binfmt_misc
+ * filesystem registration file
+ * /.build/build
+ * build script to execute once binfmts are set up
+ *
+ * AUTHOR
+ * James Perkins <james.perkins@linuxfoundation.org>
+ */
+
+#include <sys/mount.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <stdio.h>
+
+/* to enable debugging, compile with -DDEBUG */
+#ifdef DEBUG
+#define DBG(x) do { x; } while(0)
+#else
+#define DBG(x)
+#endif
+
+/* function return codes */
+enum okfail { FAIL=0, OK=1 };
+
+/* qemu registration fields, see kernel/Documentation/binfmt_misc.txt */
+enum fields { ignore=0, name, type, offset, magic, mask, interpreter, flags };
+const char * const fieldnames[] = {
+ "ignore", "name", "type", "offset",
+ "magic", "mask", "interpreter", "flags"
+};
+const int n_fields = 8;
+
+/* files in useful places */
+#define SYSFS_BINFMT_MISC "/proc/sys/fs/binfmt_misc"
+#define SYSFS_BINFMT_MISC_REG "/proc/sys/fs/binfmt_misc/register"
+#define SYSFS_BINFMT_MISC_STAT "/proc/sys/fs/binfmt_misc/status"
+
+/* /usr/lib/build/x paths are copied to /.build inside a virtual machine */
+#define BINFMT_REGF_0 "/.build/qemu-reg"
+#define BINFMT_REGF_1 "/usr/lib/build/qemu-reg"
+#define BUILD "/.build/build"
+
+/* useful constant arrays */
+static char *rx_files[] = { "/proc", "/proc/sys", "/proc/sys/fs",
+ SYSFS_BINFMT_MISC, NULL };
+static char *w_files[] = { SYSFS_BINFMT_MISC_REG, NULL };
+
+static char* const args[] = { BUILD, NULL };
+
+/* test access modes for files, return OK or FAIL */
+enum okfail test_access_files(char *files[], int mode, const char *errstr)
+{
+ int i;
+
+ for (i = 0; files[i] != NULL; i++) {
+ if (access(files[i], mode) != 0) {
+ fprintf(stderr, "%s: %s: fails test\n",
+ files[i], errstr);
+ return FAIL;
+ }
+ }
+
+ return OK;
+}
+
+/* find a string in the given file, return OK or FAIL */
+enum okfail strfile(const char *filename, const char *string)
+{
+ char buf[BUFSIZ];
+ FILE *fp;
+ enum okfail found = FAIL;
+
+ fp = fopen(filename, "r");
+ if (fp == NULL)
+ {
+ perror(filename);
+ return FAIL;
+ }
+ while (fgets(buf, sizeof(buf), fp) != NULL)
+ {
+ if (strcmp(buf, string) == 0) {
+ found = OK;
+ break;
+ }
+
+ }
+ (void)fclose(fp);
+
+ return found;
+}
+
+/* write the file with given string, return OK or FAIL */
+enum okfail write_file_string(const char *filename, const char *string)
+{
+ int fd;
+
+ if ((fd = open(filename, O_WRONLY)) == -1)
+ {
+ perror(filename);
+ return FAIL;
+ }
+
+ if (write(fd, string, strlen(string)) == -1)
+ {
+ perror("write");
+ fprintf(stderr, "%s: write failed\n", filename);
+ close(fd);
+ return FAIL;
+ }
+
+ close(fd);
+ return OK;
+}
+
+#ifdef DEBUG
+/* dump contents of the file to stderr, return OK or FAIL */
+enum okfail dump_file(char *path)
+{
+ FILE *fp;
+ char buf[BUFSIZ];
+
+ fp = fopen(path, "r");
+ if (fp == NULL) {
+ perror(path);
+ return FAIL;
+ }
+
+ while (fgets(buf, sizeof(buf), fp) != NULL)
+ {
+ fputs(buf, stderr);
+ }
+
+ fclose(fp);
+ return OK;
+}
+#endif /* DEBUG */
+
+/* parse datafile and register (to regfile) all binary formats found */
+enum okfail binfmt_register(char *datafile, char *regfile)
+{
+ char buf[BUFSIZ];
+ FILE *fp;
+ int line;
+
+ fp = fopen(datafile, "r");
+ if (fp == NULL)
+ {
+ perror(datafile);
+ return FAIL;
+ }
+
+ for (line = 1; fgets(buf, sizeof(buf), fp) != NULL; line++)
+ {
+ char tokens[BUFSIZ];
+ char *s = tokens;
+ char *f[n_fields]; /* field content pointers */
+ int n; /* current field */
+ char path[BUFSIZ];
+
+ if (buf[0] != ':') /* non-data input line */
+ {
+ goto skip;
+ }
+
+ /* copy buf and tokenize :-seperated fields into f[] */
+ strcpy(tokens, buf);
+ for (n = 0; s != NULL && n < n_fields; n++)
+ {
+ f[n] = strsep(&s, ":");
+ }
+
+#ifdef DEBUG
+ int i;
+ fprintf(stderr, "DEBUG: line %d, fields %d:\n", line, n);
+ for (i = name; i < n; i++)
+ {
+ fprintf(stderr, " %s %s\n", fieldnames[i], f[i]);
+ }
+#endif /* DEBUG */
+
+ if (n == n_fields && s != NULL)
+ {
+ fprintf(stderr, "%s: line %d: extra fields, ignoring."
+ " Content: %s", datafile, line, buf);
+ goto skip;
+ }
+
+ if (n < n_fields)
+ {
+ fprintf(stderr, "%s: line %d: missing fields, ignoring."
+ " Content: %s", datafile, line, buf);
+ goto skip;
+ }
+
+
+ if (access(f[interpreter], X_OK) != 0) {
+ fprintf(stderr,
+ "%s: line %d: interpreter '%s' not found,"
+ " ignoring\n", datafile, line, f[interpreter]);
+ goto skip;
+ }
+
+ if (!write_file_string(regfile, buf)) {
+ fprintf(stderr, "%s: line %d: write failed."
+ " Content: %s\n", datafile, line, buf);
+ (void)fclose(fp);
+ return FAIL;
+ }
+
+ /* verify registration completed correctly */
+ snprintf(path, sizeof(path), SYSFS_BINFMT_MISC "/%s", f[name]);
+
+ if (access(path, R_OK) != 0) {
+ fprintf(stderr,
+ "%s: line %d: binfmt path not created, content '%s'\n",
+ path, line, buf);
+ (void)fclose(fp);
+ return FAIL;
+ }
+
+ DBG(fprintf(stderr, "dumping: %s\n", path));
+ DBG(dump_file(path));
+
+skip:
+ ;
+ }
+
+
+ (void)fclose(fp);
+
+ return OK;
+}
+
+/* set up/verify binfmt FS support, program more binfmts, and launch build */
+int main(int argc, char* argv[], char* env[])
+{
+ int retval;
+
+ /* mount proc filesystem if it isn't already */
+ if (mount("proc", "/proc", "proc", MS_MGC_VAL, NULL) == -1) {
+ if (errno != EBUSY) {
+ perror("mount: /proc");
+ exit(1);
+ }
+ }
+
+ /* try to load binfmt module if present, no big deal if it fails */
+ if ((retval = system("/sbin/modprobe binfmt_misc")) != 0) {
+ DBG(fprintf(stderr, "modprobe binfmt_misc exit code %d\n",
+ retval));
+ }
+
+ /* mount binfmt filesystem */
+ if (mount("binfmt_misc", SYSFS_BINFMT_MISC, "binfmt_misc", MS_MGC_VAL,
+ NULL) == -1) {
+ if (errno != EBUSY) {
+ perror("mount: binfmt_misc, " SYSFS_BINFMT_MISC);
+ }
+ }
+
+ /* verify all paths resulting from this are OK */
+ if (!test_access_files(rx_files, R_OK|X_OK, "read/search")) {
+ exit(1);
+ }
+ if (!test_access_files(w_files, W_OK, "write")) {
+ exit(1);
+ }
+
+ if (!strfile("/proc/filesystems", "nodev\tbinfmt_misc\n")) {
+ fprintf(stderr,
+ "/proc/filesystems: binfmt_misc support missing\n");
+ exit(1);
+ }
+
+ if (!strfile(SYSFS_BINFMT_MISC_STAT, "enabled\n")) {
+ fprintf(stderr,
+ "%s: binfmt_misc filesystem support not enabled\n",
+ SYSFS_BINFMT_MISC_STAT);
+ exit(1);
+ }
+
+ /* setup all done, do the registration */
+ if (!binfmt_register(BINFMT_REGF_0, SYSFS_BINFMT_MISC_REG)) {
+ fprintf(stderr, "%s: failed. Trying alternate binfmt file\n",
+ BINFMT_REGF_0);
+ if (!binfmt_register(BINFMT_REGF_1, SYSFS_BINFMT_MISC_REG)) {
+ fprintf(stderr, "%s: binfmt registration failed\n",
+ BINFMT_REGF_1);
+ exit(1);
+ }
+ }
+
+ /* if we are the init process, start build */
+ if (getpid() == 1)
+ {
+ if (access(BUILD, F_OK) != 0) {
+ fprintf(stderr, "%s: build executable missing\n",
+ BUILD);
+ exit(1);
+ }
+ if (access(BUILD, X_OK) != 0) {
+ fprintf(stderr, "%s: not executable\n", BUILD);
+ exit(1);
+ }
+ execve(BUILD, args, env);
+ perror("execve");
+ exit(1);
+ }
+
+ /* success! */
+ exit(0);
+}
View
13 qemu-reg
@@ -0,0 +1,13 @@
+# register qemu binfmts
+# - used by initvm, build common_functions and init_buildsystem
+# derived from /usr/sbin/qemu-binfmt-conf.sh
+
+:arm:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff:/usr/bin/qemu-arm:
+:armeb:M::\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x28:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/usr/bin/qemu-armeb:
+:ppc:M::\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x14:\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/usr/bin/qemu-ppc:
+:mips:M::\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/usr/bin/qemu-mips:
+:mipsel:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff:/usr/bin/qemu-mipsel:
+:mipsn32:M::\x7fELF\x01\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/usr/bin/qemu-mipsn32:
+:mipsn32el:M::\x7fELF\x01\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff:/usr/bin/qemu-mipsn32el:
+:mips64:M::\x7fELF\x02\x02\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff:/usr/bin/qemu-mips64:
+:mips64el:M::\x7fELF\x02\x01\x01\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x08\x00:\xff\xff\xff\xff\xff\xff\xff\x00\xff\xff\xff\xff\xff\xff\xff\xff\xfe\xff\xff\xff:/usr/bin/qemu-mips64el:
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