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base-linux: fix ELF dataspace execution

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With this patch, if an ELF dataspace to be executed does not have a path
in the host file system, the dataspace content gets copied into a
temporary file whose path can be given to 'execve()'.

Fixes #879.
This commit is contained in:
Christian Prochaska 2013-09-09 17:59:32 +02:00 committed by Norman Feske
parent 29eeedf064
commit b0bfe6bfa7
2 changed files with 34 additions and 2 deletions
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1
base-linux/src/core/include/core_linux_syscalls.h
View File

@ -17,6 +17,7 @@
/* basic Linux syscall bindings */
#include <linux_syscalls.h>
#include <sys/stat.h>
#include <fcntl.h>
/*******************************************************

35
base-linux/src/core/pd_session_component.cc
View File

@ -364,6 +364,8 @@ int Pd_session_component::assign_parent(Parent_capability parent)
void Pd_session_component::start(Capability<Dataspace> binary)
{
const char *tmp_filename = "temporary_executable_elf_dataspace_file_for_execve";
/* lookup binary dataspace */
Object_pool<Dataspace_component>::Guard ds(_ds_ep->lookup_and_lock(binary));
@ -372,7 +374,32 @@ void Pd_session_component::start(Capability<Dataspace> binary)
return; /* XXX reflect error to client */
}
Linux_dataspace::Filename filename = ds->fname();
const char *filename = ds->fname().buf;
/*
* In order to be executable via 'execve', a program must be represented as
* a file on the Linux file system. However, this is not the case for a
* plain RAM dataspace that contains an ELF image. In this case, we copy
* the dataspace content into a temporary file whose path is passed to
* 'execve()'.
*/
if (strcmp(filename, "") == 0) {
filename = tmp_filename;
int tmp_binary_fd = lx_open(filename, O_CREAT | O_EXCL | O_WRONLY, S_IRWXU);
if (tmp_binary_fd < 0) {
PERR("Could not create file '%s'", filename);
return; /* XXX reflect error to client */
}
char buf[4096];
int num_bytes = 0;
while ((num_bytes = lx_read(ds->fd().dst().socket, buf, sizeof(buf))) != 0)
lx_write(tmp_binary_fd, buf, num_bytes);
lx_close(tmp_binary_fd);
}
/* pass parent capability as environment variable to the child */
enum { ENV_STR_LEN = 256 };
@ -412,13 +439,17 @@ void Pd_session_component::start(Capability<Dataspace> binary)
enum { STACK_SIZE = 4096 };
static char stack[STACK_SIZE]; /* initial stack used by the child until
calling 'execve' */
/*
* Argument frame as passed to 'clone'. Because, we can only pass a single
* pointer, all arguments are embedded within the 'execve_args' struct.
*/
Execve_args arg(filename.buf, _root, argv_buf, env, _uid, _gid,
Execve_args arg(filename, _root, argv_buf, env, _uid, _gid,
_parent.dst().socket);
_pid = lx_create_process((int (*)(void *))_exec_child,
stack + STACK_SIZE - sizeof(umword_t), &arg);
if (strcmp(filename, tmp_filename) == 0)
lx_unlink(filename);
};