bfd: Support dynamic expansion for massively long text lines

criu/Makefile

@@ -88,6 +88,7 @@ $(obj)/criu: $(PROGRAM-BUILTINS)
 	$(Q) $(CC) $(CFLAGS) $^ $(LDFLAGS) $(LIBS) $(WRAPFLAGS) $(GMONLDOPT) -rdynamic -o $@
 
 UNIT-BUILTINS		+= $(obj)/util.o
+UNIT-BUILTINS		+= $(obj)/bfd.o
 UNIT-BUILTINS		+= $(obj)/config.o
 UNIT-BUILTINS		+= $(obj)/log.o
 UNIT-BUILTINS		+= $(obj)/string.o

criu/bfd.c

@@ -25,6 +25,8 @@
  */
 #define BUFSIZE (PAGE_SIZE)
 
+#define BFD_MAX_DYNAMIC_SIZE (2 * 1024 * 1024)
+
 struct bfd_buf {
 	char *mem;
 	struct list_head l;
@@ -70,18 +72,24 @@ static int buf_get(struct xbuf *xb)
 
 	xb->mem = b->mem;
 	xb->data = xb->mem;
+	xb->bsize = BUFSIZE;
 	xb->sz = 0;
 	xb->buf = b;
 	return 0;
 }
 
 static void buf_put(struct xbuf *xb)
 {
-	/*
-	 * Don't unmap buffer back, it will get reused
-	 * by next bfdopen call
-	 */
-	list_add(&xb->buf->l, &bufs);
+	if (xb->buf) {
+		/*
+		 * Don't unmap standard buffer back, it will get reused
+		 * by next bfdopen call
+		 */
+		list_add(&xb->buf->l, &bufs);
+	} else {
+		/* This buffer was dynamically extended, unmap it */
+		munmap(xb->mem, xb->bsize);
+	}
 	xb->buf = NULL;
 	xb->mem = NULL;
 	xb->data = NULL;
@@ -144,7 +152,7 @@ static int brefill(struct bfd *f)
 	memmove(b->mem, b->data, b->sz);
 	b->data = b->mem;
 
-	ret = read_all(f->fd, b->mem + b->sz, BUFSIZE - b->sz);
+	ret = read_all(f->fd, b->mem + b->sz, b->bsize - b->sz);
 	if (ret < 0) {
 		pr_perror("Error reading file");
 		return -1;
@@ -172,6 +180,40 @@ char *breadline(struct bfd *f)
 	return breadchr(f, '\n');
 }
 
+static int bextend(struct bfd *f)
+{
+	struct xbuf *b = &f->b;
+	void *newbuf;
+	long newsize = b->bsize * 2;
+
+	if (newsize > BFD_MAX_DYNAMIC_SIZE) {
+		pr_err("Line too long to fit in BFD_MAX_DYNAMIC_SIZE\n");
+		return -1;
+	}
+
+	if (b->buf) {
+		newbuf = mmap(NULL, newsize, PROT_READ | PROT_WRITE,
+					     MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
+		if (newbuf == MAP_FAILED) {
+			pr_perror("Error allocating buffer");
+			return -1;
+		}
+		memcpy(newbuf, b->mem, b->sz);
+		list_add(&b->buf->l, &bufs);
+		b->buf = NULL;
+	} else {
+		newbuf = mremap(b->mem, b->bsize, newsize, MREMAP_MAYMOVE);
+		if (newbuf == MAP_FAILED) {
+			pr_perror("Error allocating buffer");
+			return -1;
+		}
+	}
+	b->mem = newbuf;
+	b->data = newbuf;
+	b->bsize = newsize;
+	return 0;
+}
+
 char *breadchr(struct bfd *f, char c)
 {
 	struct xbuf *b = &f->b;
@@ -195,9 +237,12 @@ char *breadchr(struct bfd *f, char c)
 		if (!b->sz)
 			return NULL;
 
-		if (b->sz == BUFSIZE) {
-			pr_err("The bfd buffer is too small\n");
-			return ERR_PTR(-EIO);
+		if (b->sz == b->bsize) {
+			if (bextend(f)) {
+				pr_err("The bfd buffer is too small\n");
+				return ERR_PTR(-EIO);
+			}
+			goto refill;
 		}
 		/*
 		 * Last bytes may lack the \n at the
@@ -216,6 +261,7 @@ char *breadchr(struct bfd *f, char c)
 		return b->data;
 	}
 
+refill:
 	/*
 	 * small optimization -- we've scanned b->sz
 	 * symbols already, no need to re-scan them after
@@ -252,14 +298,14 @@ static int __bwrite(struct bfd *bfd, const void *buf, int size)
 {
 	struct xbuf *b = &bfd->b;
 
-	if (b->sz + size > BUFSIZE) {
+	if (b->sz + size > b->bsize) {
 		int ret;
 		ret = bflush(bfd);
 		if (ret < 0)
 			return ret;
 	}
 
-	if (size > BUFSIZE)
+	if (size > b->bsize)
 		return write_all(bfd->fd, buf, size);
 
 	memcpy(b->data + b->sz, buf, size);

criu/include/bfd.h

@@ -8,6 +8,7 @@ struct xbuf {
 	char *mem;	 /* buffer */
 	char *data;	 /* position we see bytes at */
 	unsigned int sz; /* bytes sitting after b->pos */
+	unsigned int bsize;
 	struct bfd_buf *buf;
 };
 

criu/unittest/unit.c

@@ -1,13 +1,97 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <assert.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/mman.h>
 
 #include "log.h"
 #include "util.h"
 #include "criu-log.h"
+#include "bfd.h"
 
 int parse_statement(int i, char *line, char **configuration);
 
+static void test_bfd(void)
+{
+	struct bfd f;
+	char *str;
+	const int lines = 5;
+	char *long_line[lines];
+	int size = 1024 * 1024;
+	int i, fd;
+
+	fd = memfd_create("criu-bfd-test", 0);
+	assert(fd >= 0);
+
+	for (i = 0; i < lines; i++) {
+		int j;
+
+		long_line[i] = malloc(size + 2);
+		assert(long_line[i]);
+		long_line[i][0] = 'A' + (i % 26);
+		for (j = 1; j < size; j++)
+			long_line[i][j] = 'a' + (j % 26);
+		long_line[i][size] = '\n';
+		long_line[i][size + 1] = '\0';
+
+		assert(write(fd, long_line[i], size + 1) == size + 1);
+	}
+	assert(lseek(fd, 0, SEEK_SET) == 0);
+
+	f.fd = fd;
+	assert(bfdopenr(&f) == 0);
+
+	for (i = 0; i < lines; i++) {
+		str = breadline(&f);
+		assert(str);
+		assert(strlen(str) == size);
+		/* long_line has \n, str hasn't */
+		assert(strcmp(str, long_line[i]) != 0);
+		str[size] = '\n';
+		assert(memcmp(str, long_line[i], size + 1) == 0);
+	}
+
+	bclose(&f);
+	for (i = 0; i < lines; i++)
+		free(long_line[i]);
+}
+
+static void test_bwrite(void)
+{
+	struct bfd f;
+	char *buf;
+	int size = 1024 * 1024;
+	int i;
+	int fd;
+	char *read_buf;
+
+	fd = memfd_create("criu-bfd-test", 0);
+	assert(fd >= 0);
+
+	buf = malloc(size);
+	assert(buf);
+	for (i = 0; i < size; i++)
+		buf[i] = 'z' - (i % 26);
+
+	f.fd = dup(fd);
+	assert(f.fd >= 0);
+	assert(bfdopenw(&f) == 0);
+
+	assert(bwrite(&f, buf, size) == size);
+	bclose(&f);
+
+	assert(lseek(fd, 0, SEEK_SET) == 0);
+	read_buf = malloc(size);
+	assert(read_buf);
+	assert(read(fd, read_buf, size) == size);
+	assert(memcmp(buf, read_buf, size) == 0);
+
+	close(fd);
+	free(buf);
+	free(read_buf);
+}
+
 int main(int argc, char *argv[], char *envp[])
 {
 	char **configuration;
@@ -16,6 +100,9 @@ int main(int argc, char *argv[], char *envp[])
 	configuration = malloc(10 * sizeof(char *));
 	log_init(NULL);
 
+	test_bfd();
+	test_bwrite();
+
 	i = parse_statement(0, "", configuration);
 	assert(i == 0);
 

test/zdtm.py

@@ -511,6 +511,10 @@ def start(self):
         else:
             print("Test is SUID")
 
+        if test_flag(self.__desc, 'ext-uid-map'):
+            env['ZDTM_UID_MAP'] = "0 0 4294967295"
+            env['ZDTM_GID_MAP'] = "0 0 4294967295"
+
         if self.__flavor.ns:
             env['ZDTM_NEWNS'] = "1"
             env['ZDTM_ROOT'] = self.__flavor.root

test/zdtm/lib/ns.c

@@ -492,15 +492,20 @@ void ns_create(int argc, char **argv)
 		char pname[PATH_MAX];
 		int fd;
 
+		char *ext_uid_map = getenv("ZDTM_UID_MAP");
+		char *ext_gid_map = getenv("ZDTM_GID_MAP");
+
 		snprintf(pname, sizeof(pname), "/proc/%d/uid_map", pid);
 		fd = open(pname, O_WRONLY);
 		if (fd < 0) {
 			fprintf(stderr, "open(%s): %m\n", pname);
 			exit(1);
 		}
-		if (write(fd, UID_MAP, sizeof(UID_MAP)) < 0) {
-			fprintf(stderr, "write(" UID_MAP "): %m\n");
-			exit(1);
+
+		if (ext_uid_map) {
+			dprintf(fd, "%s", ext_uid_map);
+		} else {
+			write(fd, UID_MAP, sizeof(UID_MAP) - 1);
 		}
 		close(fd);
 
@@ -510,9 +515,11 @@ void ns_create(int argc, char **argv)
 			fprintf(stderr, "open(%s): %m\n", pname);
 			exit(1);
 		}
-		if (write(fd, GID_MAP, sizeof(GID_MAP)) < 0) {
-			fprintf(stderr, "write(" GID_MAP "): %m\n");
-			exit(1);
+
+		if (ext_gid_map) {
+			dprintf(fd, "%s", ext_gid_map);
+		} else {
+			write(fd, GID_MAP, sizeof(GID_MAP) - 1);
 		}
 		close(fd);
 	}

test/zdtm/static/Makefile

@@ -287,6 +287,7 @@ TST_NOFILE	:=				\
 		sigtrap01			\
 		change_mnt_context		\
 		fd_offset			\
+		massive_groups			\
 #		jobctl00			\
 
 PKG_CONFIG ?= pkg-config
@@ -736,6 +737,8 @@ cgroupv2_01:		LDLIBS += -pthread
 uprobes:		CFLAGS += $(call pkg-cflags, libtracefs libtraceevent)
 uprobes:		LDLIBS += $(call pkg-libs, libtracefs libelf)
 
+massive_groups:	LDLIBS += -lrt -pthread
+
 $(LIB):	force
 	$(Q) $(MAKE) -C $(LIBDIR)