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Don't call realpath(3) from libmap rtld code. This gets rid of a few calls

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to fstatat(2) at binary startup; the difference looks like this:

--- przed       2017-10-14 13:55:49.983528000 +0100
+++ po  2017-10-14 14:10:39.134343000 +0100
@@ -1,15 +1,10 @@
 mmap(0x0,32768,PROT_READ|PROT_WRITE,MAP_PRIVATE|MAP_ANON,-1,0x0) = 34366173184 (0x800623000)
 issetugid()                                     = 0 (0x0)
-fstatat(AT_FDCWD,"/etc",{ mode=drwxr-xr-x ,inode=1364352,size=2560,blksize=32768 },AT_SYMLINK_NOFOLLOW) = 0 (0x0)
-fstatat(AT_FDCWD,"/etc/libmap.conf",{ mode=-rw-r--r-- ,inode=1373288,size=102,blksize=32768 },AT_SYMLINK_NOFOLLOW) = 0 (0x0)
 openat(AT_FDCWD,"/etc/libmap.conf",O_RDONLY|O_CLOEXEC,00) = 3 (0x3)
 fstat(3,{ mode=-rw-r--r-- ,inode=1373288,size=102,blksize=32768 }) = 0 (0x0)
 mmap(0x0,102,PROT_READ,MAP_PRIVATE,3,0x0)       = 34366205952 (0x80062b000)
 close(3)                                        = 0 (0x0)
-fstatat(AT_FDCWD,"/usr",{ mode=drwxr-xr-x ,inode=561792,size=512,blksize=32768 },AT_SYMLINK_NOFOLLOW) = 0 (0x0)
-fstatat(AT_FDCWD,"/usr/local",{ mode=drwxr-xr-x ,inode=561800,size=512,blksize=32768 },AT_SYMLINK_NOFOLLOW) = 0 (0x0)
-fstatat(AT_FDCWD,"/usr/local/etc",{ mode=drwxr-xr-x ,inode=653279,size=1536,blksize=32768 },AT_SYMLINK_NOFOLLOW) = 0 (0x0)
-fstatat(AT_FDCWD,"/usr/local/etc/libmap.d",0x7fffffffcf50,AT_SYMLINK_NOFOLLOW) ERR#2 'No such file or directory'
+open("/usr/local/etc/libmap.d",O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC,0165) ERR#2 'No such file or directory'
 munmap(0x80062b000,102)                                 = 0 (0x0)
 openat(AT_FDCWD,"/var/run/ld-elf.so.hints",O_RDONLY|O_CLOEXEC,00) = 3 (0x3)
 read(3,"Ehnt\^A\0\0\0\M^@\0\0\0\M-2\0\0"...,128) = 128 (0x80)

Reviewed by:	kib
MFC after:	2 weeks
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D12741
This commit is contained in:
trasz 2017-10-22 10:32:40 +00:00
parent d836be949c
commit ae63a24a87
1 changed files with 23 additions and 28 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

51
libexec/rtld-elf/libmap.c
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@ -36,6 +36,8 @@ struct lmp {
static TAILQ_HEAD(lmc_list, lmc) lmc_head = TAILQ_HEAD_INITIALIZER(lmc_head);
struct lmc {
char *path;
dev_t dev;
ino_t ino;
TAILQ_ENTRY(lmc) next;
};
@ -99,45 +101,45 @@ lmc_parse_file(char *path)
struct lmc *p;
struct stat st;
int fd;
char *rpath;
char *lm_map;
rpath = realpath(path, NULL);
if (rpath == NULL)
return;
TAILQ_FOREACH(p, &lmc_head, next) {
if (strcmp(p->path, rpath) == 0) {
free(rpath);
if (strcmp(p->path, path) == 0)
return;
}
}
fd = open(rpath, O_RDONLY | O_CLOEXEC);
fd = open(path, O_RDONLY | O_CLOEXEC);
if (fd == -1) {
dbg("lm_parse_file: open(\"%s\") failed, %s", rpath,
dbg("lm_parse_file: open(\"%s\") failed, %s", path,
rtld_strerror(errno));
free(rpath);
return;
}
if (fstat(fd, &st) == -1) {
close(fd);
dbg("lm_parse_file: fstat(\"%s\") failed, %s", rpath,
dbg("lm_parse_file: fstat(\"%s\") failed, %s", path,
rtld_strerror(errno));
free(rpath);
return;
}
TAILQ_FOREACH(p, &lmc_head, next) {
if (p->dev == st.st_dev && p->ino == st.st_ino) {
close(fd);
return;
}
}
lm_map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
if (lm_map == (const char *)MAP_FAILED) {
close(fd);
dbg("lm_parse_file: mmap(\"%s\") failed, %s", rpath,
dbg("lm_parse_file: mmap(\"%s\") failed, %s", path,
rtld_strerror(errno));
free(rpath);
return;
}
close(fd);
p = xmalloc(sizeof(struct lmc));
p->path = rpath;
p->path = xstrdup(path);
p->dev = st.st_dev;
p->ino = st.st_ino;
TAILQ_INSERT_HEAD(&lmc_head, p, next);
lmc_parse(lm_map, st.st_size);
munmap(lm_map, st.st_size);
@ -151,26 +153,19 @@ lmc_parse_dir(char *idir)
struct lmc *p;
char conffile[MAXPATHLEN];
char *ext;
char *rpath;
rpath = realpath(idir, NULL);
if (rpath == NULL)
return;
TAILQ_FOREACH(p, &lmc_head, next) {
if (strcmp(p->path, rpath) == 0) {
free(rpath);
if (strcmp(p->path, idir) == 0)
return;
}
}
d = opendir(idir);
if (d == NULL) {
free(rpath);
if (d == NULL)
return;
}
p = xmalloc(sizeof(struct lmc));
p->path = rpath;
p->path = xstrdup(idir);
p->dev = NODEV;
p->ino = 0;
TAILQ_INSERT_HEAD(&lmc_head, p, next);
while ((dp = readdir(d)) != NULL) {