Am 27.07.2013 17:23, schrieb Gabriel de Perthuis:
> Useful for
> * limiting privileges
> * opening block devices O_EXCL
So, the goal of this patch is to allow passing a file descriptor
number as block device instead of a file?
I assume you have already a wrapper around UML which exec()'s it such that
it can reuse a fd?
> Use dup to work around the fact /proc/self/fd
> can't be opened after dropping privileges.
> This proc behaviour doesn't match TLPI and might be a bug.
>
> Qemu has a slightly more complex fdset approach
> that provides fds with different access permissions.
I really don't like that you patch os_open_file(), this is a
generic function.
What about this one?
Allow ubda= (and all other UML block device kernel parameters) to
accept arguments like file:/foo/bar and fd:N.
Where N is a number and file: is default such that we do not break
old kernels.
Thanks,
//richard
> Signed-off-by: Gabriel de Perthuis <g2p.c...@gmail.com>
> ---
> arch/um/os-Linux/file.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/arch/um/os-Linux/file.c b/arch/um/os-Linux/file.c
> index c17bd6f..cee65ba 100644
> --- a/arch/um/os-Linux/file.c
> +++ b/arch/um/os-Linux/file.c
> @@ -169,11 +169,11 @@ int os_file_mode(const char *file, struct openflags
> *mode_out)
> return err;
> }
>
> int os_open_file(const char *file, struct openflags flags, int mode)
> {
> - int fd, err, f = 0;
> + int fd, fd0, err, f = 0;
>
> if (flags.r && flags.w)
> f = O_RDWR;
> else if (flags.r)
> f = O_RDONLY;
> @@ -190,11 +190,15 @@ int os_open_file(const char *file, struct openflags
> flags, int mode)
> if (flags.e)
> f |= O_EXCL;
> if (flags.a)
> f |= O_APPEND;
>
> - fd = open64(file, f, mode);
> + if (!strncmp(file, "/dev/fd/", 8)
> + && sscanf(file, "/dev/fd/%d", &fd0) == 1)
> + fd = dup(fd0);
> + else
> + fd = open64(file, f, mode);
> if (fd < 0)
> return -errno;
>
> if (flags.cl && fcntl(fd, F_SETFD, 1)) {
> err = -errno;
> @@ -280,11 +284,11 @@ int os_file_size(const char *file, unsigned long long
> *size_out)
>
> if (S_ISBLK(buf.ust_mode)) {
> int fd;
> long blocks;
>
> - fd = open(file, O_RDONLY, 0);
> + fd = os_open_file(file, of_read(OPENFLAGS()), 0);
> if (fd < 0) {
> err = -errno;
> printk(UM_KERN_ERR "Couldn't open \"%s\", "
> "errno = %d\n", file, errno);
> return err;
>
------------------------------------------------------------------------------
See everything from the browser to the database with AppDynamics
Get end-to-end visibility with application monitoring from AppDynamics
Isolate bottlenecks and diagnose root cause in seconds.
Start your free trial of AppDynamics Pro today!
http://pubads.g.doubleclick.net/gampad/clk?id=48808831&iu=/4140/ostg.clktrk
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel
