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# This patchset updates the libbb stuff to use a vfork() version of
# gz_open, called gzvopen. This is done because a standard fork will
# duplicate the entire address space. This will invoke the OOM
# (out of memory) killer on small-memory machines, because most often
# by the time we unzip any package, we've read the entire package
# database into memory already. By using vfork() and immediatly
# execing the external gunzip utility, we avoid the need to clone the
# entire address space.
#
# Yes, this is actually **LESS** efficient than the original way!
# But there is no way to (currently) dodge the OOM killer on a
# per-process basis, so the alternatives are to either change the
# OOM killer behavior system-wide, or to use this workaround.
#
# Mike Westerhof, Dec 2008
--- orig/libbb/gz_open.c 2008-03-01 12:55:33.000000000 -0600
+++ opkg/libbb/gz_open.c 2008-12-21 21:41:13.000000000 -0600
@@ -56,3 +56,78 @@
}
return(fdopen(unzip_pipe[0], "r"));
}
+
+/* gz_open implementation using gunzip and a vfork/exec -- dodges OOM killer */
+extern FILE *gzvopen(FILE *compressed_file, int *pid)
+{
+ int unzip_pipe[2];
+ off_t floc;
+ int cfile;
+
+ /* create a new file descriptor for the input stream
+ * (it *must* be associated with a file)
+ * and seek to the same position in that fd as the stream.
+ */
+ cfile = dup(fileno(compressed_file));
+ floc = ftello(compressed_file);
+ lseek(cfile, floc, SEEK_SET);
+
+ /* create the pipe */
+ if (pipe(unzip_pipe)!=0) {
+ error_msg("gzvopen(): pipe error");
+ return(NULL);
+ }
+
+ *pid = vfork();
+
+ if (*pid < 0) {
+ error_msg("gzvopen(): fork failed");
+ return(NULL);
+ }
+
+ if (*pid==0) {
+ /* child process - reads STDIN, writes to pipe */
+
+ /* close unused read end of pipe */
+ close(unzip_pipe[0]);
+
+ /* connect child's stdout to the pipe write end */
+ dup2(unzip_pipe[1], 1);
+
+ /* connect child's stdin to the fd passed in to us */
+ dup2(cfile, 0);
+
+ /* execute the gunzip utility */
+ execlp("gunzip","gunzip",NULL);
+
+ /* if we get here, we had a failure - since we are
+ * using vfork(), we cannot call exit(), must call _exit().
+ */
+ _exit(-1);
+ }
+
+ /* Parent process is executing here */
+
+ /* we have no more need of the duplicate fd */
+ close(cfile);
+
+ /* close the write end of the pipe */
+ close(unzip_pipe[1]);
+
+ /* return the read end of the pipe as a FILE */
+ return(fdopen(unzip_pipe[0], "r"));
+}
+
+extern void gzvclose(int gunzip_pid)
+{
+ if (kill(gunzip_pid, SIGTERM) == -1) {
+ perror("gzvclose()");
+ fprintf(stderr,"%s: unable to kill gunzip pid.\n",
+ __FUNCTION__);
+ }
+
+ if (waitpid(gunzip_pid, NULL, 0) == -1) {
+ fprintf(stderr,"%s: unable to wait on gunzip pid.\n",
+ __FUNCTION__);
+ }
+}
--- orig/libbb/libbb.h 2008-12-20 15:06:51.000000000 -0600
+++ opkg/libbb/libbb.h 2008-12-21 21:41:13.000000000 -0600
@@ -270,6 +270,8 @@
extern int unzip(FILE *l_in_file, FILE *l_out_file);
extern void gz_close(int gunzip_pid);
extern FILE *gz_open(FILE *compressed_file, int *pid);
+extern void gzvclose(int gunzip_pid);
+extern FILE *gzvopen(FILE *compressed_file, int *pid);
extern struct hostent *xgethostbyname(const char *name);
extern int create_icmp_socket(void);
--- orig/libbb/unarchive.c 2008-09-10 11:48:23.000000000 -0500
+++ opkg/libbb/unarchive.c 2008-12-21 21:41:13.000000000 -0600
@@ -749,7 +749,7 @@
while ((ar_header = get_header_ar(deb_stream)) != NULL) {
if (strcmp(ared_file, ar_header->name) == 0) {
/* open a stream of decompressed data */
- uncompressed_stream = gz_open(deb_stream, &gunzip_pid);
+ uncompressed_stream = gzvopen(deb_stream, &gunzip_pid);
archive_offset = 0;
output_buffer = unarchive(uncompressed_stream, out_stream, get_header_tar, free_header_tar, extract_function, prefix, file_list);
}
@@ -757,7 +757,7 @@
free (ar_header->name);
free (ar_header);
}
- gz_close(gunzip_pid);
+ gzvclose(gunzip_pid);
fclose(deb_stream);
fclose(uncompressed_stream);
free(ared_file);
@@ -769,7 +769,7 @@
file_header_t *tar_header;
archive_offset = 0;
fseek(deb_stream, 0, SEEK_SET);
- unzipped_opkg_stream = gz_open(deb_stream, &unzipped_opkg_pid);
+ unzipped_opkg_stream = gzvopen(deb_stream, &unzipped_opkg_pid);
/*fprintf(stderr, __FUNCTION__ ": processing opkg %s -- ared_file=%s\n", package_filename, ared_file);*/
/* walk through outer tar file to find ared_file */
@@ -779,7 +779,7 @@
name_offset = 2;
if (strcmp(ared_file, tar_header->name+name_offset) == 0) {
/* open a stream of decompressed data */
- uncompressed_stream = gz_open(unzipped_opkg_stream, &gunzip_pid);
+ uncompressed_stream = gzvopen(unzipped_opkg_stream, &gunzip_pid);
archive_offset = 0;
/*fprintf(stderr, __FUNCTION__ ":%d: here -- found file\n", __LINE__);*/
output_buffer = unarchive(uncompressed_stream,
@@ -791,14 +791,14 @@
file_list);
/*fprintf(stderr, __FUNCTION__ ":%d: unarchive complete\n", __LINE__);*/
free_header_tar(tar_header);
- gz_close(gunzip_pid);
+ gzvclose(gunzip_pid);
fclose(uncompressed_stream);
break;
}
seek_sub_file(unzipped_opkg_stream, tar_header->size);
free_header_tar(tar_header);
}
- gz_close(unzipped_opkg_pid);
+ gzvclose(unzipped_opkg_pid);
fclose(unzipped_opkg_stream);
fclose(deb_stream);
free(ared_file);
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