[uml-devel] PATCH check for sys_sendfile() in port_user.c

[uml-devel] PATCH check for sys_sendfile() in port_user.c

[Dan Shearer]

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Some kernels (including SuSE 2.4.20, according to
http://marc.theaimsgroup.com/?l=user-mode-linux-user&m=107437381718023&w=2)
don't have sys_sendfile, in which case the port console driver should
refuse to start up because there is no way for telnetd to get the fd.
This might not be obvious to debug.

NOTE! Not tested because it doesn't bite me! Beyond the fact that it
works on systems *with* sendfile() :-)

Should be the final word in anyone who wants to throw out commandline
parameter passing for xterm in favour of fd passing.

(And one more tiny little portability aid.)

-- 
Dan Shearer
dan@shearer.org

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--- port_user.c.orig	2004-01-24 15:48:53.000000000 +1030
+++ port_user.c	2004-01-27 15:05:40.000000000 +1030
@@ -35,6 +35,11 @@
 	char *end;
 	int port;
 
+	if(sys_sendfile() == -1){
+		printk("port_init : host kernel doesn't support sendfile()\n");
+		return(NULL);
+	}
+
 	if(*str != ':'){
 		printk("port_init : channel type 'port' must specify a "
 		       "port number\n");

Re: [uml-devel] PATCH check for sys_sendfile() in port_user.c

[Jeff Dike]

> Some kernels (including SuSE 2.4.20, according to http://
> marc.theaimsgroup.com/?l=user-mode-linux-user&m=107437381718023&w=2)
> don't have sys_sendfile, in which case the port console driver should
> refuse to start up because there is no way for telnetd to get the fd. 

sendfile has nothing to do with passing descriptors across unix sockets.
It is a relatively new performance tweak which allows files to be copied
without the data flowing through userspace.

				Jeff



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