diff options
author | Andre Przywara <andre.przywara@arm.com> | 2015-10-30 18:26:55 +0000 |
---|---|---|
committer | Will Deacon <will.deacon@arm.com> | 2015-11-18 10:50:02 +0000 |
commit | 649f9515e623adf982c4e9a9922cfce173fd9de8 (patch) | |
tree | 9d332c8ca403e357bdaf6f14f50ceab962e5cd23 | |
parent | 004f76848ebf121ad444c48a46b4f3ab7c14784f (diff) | |
download | kvmtool-649f9515e623adf982c4e9a9922cfce173fd9de8.tar.gz |
provide generic read_file() implementation
In various parts of kvmtool we simply try to read files into memory,
but fail to do so in a safe way. The read(2) syscall can return early
having only parts of the file read, or it may return -1 due to being
interrupted by a signal (in which case we should simply retry).
The ARM code seems to provide the only safe implementation, so take
that as an inspiration to provide a generic read_file() function
usable by every part of kvmtool.
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
-rw-r--r-- | include/kvm/read-write.h | 2 | ||||
-rw-r--r-- | util/read-write.c | 21 |
2 files changed, 23 insertions, 0 deletions
diff --git a/include/kvm/read-write.h b/include/kvm/read-write.h index 67571f96..acbd6f0b 100644 --- a/include/kvm/read-write.h +++ b/include/kvm/read-write.h @@ -12,6 +12,8 @@ ssize_t xread(int fd, void *buf, size_t count); ssize_t xwrite(int fd, const void *buf, size_t count); +ssize_t read_file(int fd, char *buf, size_t max_size); + ssize_t read_in_full(int fd, void *buf, size_t count); ssize_t write_in_full(int fd, const void *buf, size_t count); diff --git a/util/read-write.c b/util/read-write.c index 44709dfd..bf6fb2fc 100644 --- a/util/read-write.c +++ b/util/read-write.c @@ -32,6 +32,27 @@ restart: return nr; } +/* + * Read in the whole file while not exceeding max_size bytes of the buffer. + * Returns -1 (with errno set) in case of an error (ENOMEM if buffer was + * too small) or the filesize if the whole file could be read. + */ +ssize_t read_file(int fd, char *buf, size_t max_size) +{ + ssize_t ret; + char dummy; + + errno = 0; + ret = read_in_full(fd, buf, max_size); + + /* Probe whether we reached EOF. */ + if (xread(fd, &dummy, 1) == 0) + return ret; + + errno = ENOMEM; + return -1; +} + ssize_t read_in_full(int fd, void *buf, size_t count) { ssize_t total = 0; |