Date: Wed, 17 Jun 2009 11:14:26 GMT From: Robert Watson <rwatson@FreeBSD.org> To: Perforce Change Reviews <perforce@freebsd.org> Subject: PERFORCE change 164566 for review Message-ID: <200906171114.n5HBEQV9060382@repoman.freebsd.org>
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http://perforce.freebsd.org/chv.cgi?CH=164566 Change 164566 by rwatson@rwatson_freebsd_capabilities on 2009/06/17 11:14:10 Update rtld-elf-cap.1 to reflect recent changes. Affected files ... .. //depot/projects/trustedbsd/capabilities/src/libexec/rtld-elf-cap/rtld-elf-cap.1#5 edit Differences ... ==== //depot/projects/trustedbsd/capabilities/src/libexec/rtld-elf-cap/rtld-elf-cap.1#5 (text+ko) ==== @@ -45,34 +45,51 @@ is a version of .Xr ld-elf.so.1 1 specific to the sandbox environment created using +.Xr libcapability 3 , +which provides certain extended or modified linker services for that +environment: +.Bl -bullet +.It +Will not attempt to use global file system namespaces that are not available +when running under .Xr cap_enter 2 . -.Nm -is intended to be directly executed using the -.Xr fexeve 2 -system call, and expects the binary to be passed as file descriptor -.Dv 3 , -as well as additional libraries described by the +.It +Expects to be directly executed using +.Xr fexecve 2 , +with the desired binary to run passed as file descriptor 3. +.It +Recognizes the addition symbol +.Dv cap_main , +which will be used in preference to the normal ELF entry point for a binary +when in sandbox mode. +This makes it easy a single binary to select different behavior when run in +the different environments. +.It Interprets the .Dv LD_CAPLIBINDEX -environmental variable. +environmental variable set by sandbox start touines, and implements +.Fn ld_capibindex_lookup , +allowing file descriptors for binaries and libraries passed across +.Xr fexecve 2 +to be used by +.Xr libcapability 3 , +as well as applications. +.It +Implements a version of +.Fn ld_insandbox +that returns true, overriding the libc function that returns false. +.El .Pp -Binaries for the sandbox environment are normal, dynamically linked binaries -as created by -.Xr gcc 1 . -As with traditional -.Fx -binaries, the C run-time expects to begin execution with a -.Dv main -function which will be passed execution-time arguments explicitly, as well -as having access to inherited environmental variables. +Applications using +.Dv cap_main +will need to export it as a dynamic symbol, perhaps using +.Xr gcc 1 's +.Dv -rdynamic +command line flag. .Pp Most capability-mode applications will be started using the APIs defined in .Xr libcapability 3 , which properly set up the run-time environment for .Nm . -.Sh IMPLEMENTATION NOTES -Linking sandbox binaries as relocatable shared objects rather than linking -them with a fixed virtual address allows them to be directly linked into -consumers, if desired, for debugging or performance analysis purposes. .Sh SEE ALSO .Xr gcc 1 , .Xr ld-elf.so.1 1 ,
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