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DynamicLoader: Add an option to explicitly run an ELF executable binary

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If the user runs /usr/lib/Loader.so and pass a second string to argv, we
will try to run it as if it was running that program without invoking
the dynamic loader explicitly.
This commit is contained in:
Liav A 2023-09-08 20:30:35 +03:00 committed by Daniel Bertalan
parent a3073824a9
commit 81169ee6e6
Notes: sideshowbarker 2024-07-17 22:01:16 +09:00 
Author: https://github.com/supercomputer7
Commit: https://github.com/SerenityOS/serenity/commit/81169ee6e6
Pull-request: https://github.com/SerenityOS/serenity/pull/20988
Reviewed-by: https://github.com/ADKaster
Reviewed-by: https://github.com/BertalanD ✅
Reviewed-by: https://github.com/kleinesfilmroellchen ✅
1 changed files with 47 additions and 7 deletions
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54
Userland/DynamicLoader/main.cpp
View file

@ -4,10 +4,14 @@
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/ScopeGuard.h>
#include <Kernel/API/POSIX/sys/stat.h>
#include <LibELF/AuxiliaryVector.h>
#include <LibELF/DynamicLinker.h>
#include <LibELF/Relocation.h>
#include <fcntl.h>
#include <sys/internals.h>
#include <syscall.h>
#include <unistd.h>
char* __static_environ[] = { nullptr }; // We don't get the environment without some libc workarounds..
@ -49,8 +53,8 @@ kernel to load this program.
This helper program loads the shared libraries needed by the program,
prepares the program to run, and runs it. You do not need to invoke
this helper program directly.
)";
this helper program directly. If you still want to run a program with the loader,
run: /usr/lib/Loader.so [ELF_BINARY])";
fprintf(stderr, "%s", message);
}
@ -76,6 +80,30 @@ NAKED void _start(int, char**, char**)
#endif
}
static ErrorOr<int> open_executable(char const* path)
{
int rc = open(path, O_RDONLY | O_EXEC);
if (rc < 0)
return Error::from_errno(errno);
int checked_fd = rc;
ArmedScopeGuard close_on_failure([checked_fd] {
close(checked_fd);
});
struct stat executable_stat = {};
rc = fstat(checked_fd, &executable_stat);
if (rc < 0)
return Error::from_errno(errno);
if (!S_ISREG(executable_stat.st_mode)) {
if (S_ISDIR(executable_stat.st_mode))
return Error::from_errno(EISDIR);
return Error::from_errno(EINVAL);
}
close_on_failure.disarm();
return checked_fd;
}
void _entry(int argc, char** argv, char** envp)
{
char** env;
@ -103,11 +131,23 @@ void _entry(int argc, char** argv, char** envp)
if (main_program_path == "/usr/lib/Loader.so"sv) {
// We've been invoked directly as an executable rather than as the
// ELF interpreter for some other binary. In the future we may want
// to support launching a program directly from the dynamic loader
// like ld.so on Linux.
display_help();
_exit(1);
// ELF interpreter for some other binary. The second argv string should
// be the path to the ELF executable, and if we don't have enough strings in argv
// (argc < 2), just fail with message to stderr about this.
if (argc < 2) {
display_help();
_exit(1);
}
auto error_or_fd = open_executable(argv[1]);
if (error_or_fd.is_error()) {
warnln("Loader.so: Loading {} failed: {}", argv[1], strerror(error_or_fd.error().code()));
_exit(1);
}
main_program_fd = error_or_fd.release_value();
main_program_path = argv[1];
argv++;
argc--;
}
VERIFY(main_program_fd >= 0);