[PATCH v3 4/8] gen_init_cpio: avoid duplicate strlen calls

David Disseldorp
2025-08-19T03:50:26Z

We determine the filename length for the cpio header, so shouldn't
recalculate it when writing out the filename.

Signed-off-by: David Disseldorp <ddiss@suse.de>
Reviewed-by: Nicolas Schier <nsc@kernel.org>
---
usr/gen_init_cpio.c | 40 ++++++++++++++++++++++++----------------
1 file changed, 24 insertions(+), 16 deletions(-)

diff --git a/usr/gen_init_cpio.c b/usr/gen_init_cpio.c
index aa73afd3756c8..729585342e16e 100644
--- a/usr/gen_init_cpio.c
+++ b/usr/gen_init_cpio.c
@@ -25,6 +25,7 @@
#define str(s) xstr(s)
#define MIN(a, b) ((a) < (b) ? (a) : (b))
#define CPIO_HDR_LEN 110
+#define CPIO_TRAILER "TRAILER!!!"
#define padlen(_off, _align) (((_align) - ((_off) & ((_align) - 1))) % (_align))

static char padding[512];
@@ -40,9 +41,8 @@ struct file_handler {
int (*handler)(const char *line);
};

-static int push_string(const char *name)
+static int push_buf(const char *name, size_t name_len)
{
- unsigned int name_len = strlen(name) + 1;
ssize_t len;

len = write(outfd, name, name_len);
@@ -69,9 +69,8 @@ static int push_pad(size_t padlen)
return 0;
}

-static int push_rest(const char *name)
+static int push_rest(const char *name, size_t name_len)
{
- unsigned int name_len = strlen(name) + 1;
ssize_t len;

len = write(outfd, name, name_len);
@@ -85,8 +84,8 @@ static int push_rest(const char *name)

static int cpio_trailer(void)
{
- const char name[] = "TRAILER!!!";
int len;
+ unsigned int namesize = sizeof(CPIO_TRAILER);

len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
"%08X%08X%08X%08X%08X%08X%08X",
@@ -102,12 +101,12 @@ static int cpio_trailer(void)
0, /* minor */
0, /* rmajor */
0, /* rminor */
- (unsigned)strlen(name)+1, /* namesize */
+ namesize, /* namesize */
0); /* chksum */
offset += len;

if (len != CPIO_HDR_LEN ||
- push_rest(name) < 0 ||
+ push_rest(CPIO_TRAILER, namesize) < 0 ||
push_pad(padlen(offset, 512)) < 0)
return -1;

@@ -118,9 +117,12 @@ static int cpio_mkslink(const char *name, const char *target,
unsigned int mode, uid_t uid, gid_t gid)
{
int len;
+ unsigned int namesize, targetsize = strlen(target) + 1;

if (name[0] == '/')
name++;
+ namesize = strlen(name) + 1;
+
len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
"%08X%08X%08X%08X%08X%08X%08X",
do_csum ? "070702" : "070701", /* magic */
@@ -130,19 +132,19 @@ static int cpio_mkslink(const char *name, const char *target,
(long) gid, /* gid */
1, /* nlink */
(long) default_mtime, /* mtime */
- (unsigned)strlen(target)+1, /* filesize */
+ targetsize, /* filesize */
3, /* major */
1, /* minor */
0, /* rmajor */
0, /* rminor */
- (unsigned)strlen(name) + 1,/* namesize */
+ namesize, /* namesize */
0); /* chksum */
offset += len;

if (len != CPIO_HDR_LEN ||
- push_string(name) < 0 ||
+ push_buf(name, namesize) < 0 ||
push_pad(padlen(offset, 4)) < 0 ||
- push_string(target) < 0 ||
+ push_buf(target, targetsize) < 0 ||
push_pad(padlen(offset, 4)) < 0)
return -1;

@@ -172,9 +174,12 @@ static int cpio_mkgeneric(const char *name, unsigned int mode,
uid_t uid, gid_t gid)
{
int len;
+ unsigned int namesize;

if (name[0] == '/')
name++;
+ namesize = strlen(name) + 1;
+
len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
"%08X%08X%08X%08X%08X%08X%08X",
do_csum ? "070702" : "070701", /* magic */
@@ -189,12 +194,12 @@ static int cpio_mkgeneric(const char *name, unsigned int mode,
1, /* minor */
0, /* rmajor */
0, /* rminor */
- (unsigned)strlen(name) + 1,/* namesize */
+ namesize, /* namesize */
0); /* chksum */
offset += len;

if (len != CPIO_HDR_LEN ||
- push_rest(name) < 0)
+ push_rest(name, namesize) < 0)
return -1;

return 0;
@@ -265,6 +270,7 @@ static int cpio_mknod(const char *name, unsigned int mode,
unsigned int maj, unsigned int min)
{
int len;
+ unsigned int namesize;

if (dev_type == 'b')
mode |= S_IFBLK;
@@ -273,6 +279,8 @@ static int cpio_mknod(const char *name, unsigned int mode,

if (name[0] == '/')
name++;
+ namesize = strlen(name) + 1;
+
len = dprintf(outfd, "%s%08X%08X%08lX%08lX%08X%08lX"
"%08X%08X%08X%08X%08X%08X%08X",
do_csum ? "070702" : "070701", /* magic */
@@ -287,12 +295,12 @@ static int cpio_mknod(const char *name, unsigned int mode,
1, /* minor */
maj, /* rmajor */
min, /* rminor */
- (unsigned)strlen(name) + 1,/* namesize */
+ namesize, /* namesize */
0); /* chksum */
offset += len;

if (len != CPIO_HDR_LEN ||
- push_rest(name) < 0)
+ push_rest(name, namesize) < 0)
return -1;

return 0;
@@ -426,7 +434,7 @@ static int cpio_mkfile(const char *name, const char *location,
offset += len;

if (len != CPIO_HDR_LEN ||
- push_string(name) < 0 ||
+ push_buf(name, namesize) < 0 ||
push_pad(padlen(offset, 4)) < 0)
goto error;

--
2.43.0