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#include <sys/ptrace.h>
#include <sys/prctl.h>
#include <asm/unistd.h>
#include <sysdep/stub.h>
#include <stub-data.h>
void _start(void);
noinline static void real_init(void)
{
struct stub_init_data init_data;
unsigned long res;
struct {
void *ss_sp;
int ss_flags;
size_t ss_size;
} stack = {
.ss_size = STUB_DATA_PAGES * UM_KERN_PAGE_SIZE,
};
struct {
void *sa_handler_;
unsigned long sa_flags;
void *sa_restorer;
unsigned long long sa_mask;
} sa = {
/* Need to set SA_RESTORER (but the handler never returns) */
.sa_flags = SA_ONSTACK | SA_NODEFER | SA_SIGINFO | 0x04000000,
/* no need to mask any signals */
.sa_mask = 0,
};
/* set a nice name */
stub_syscall2(__NR_prctl, PR_SET_NAME, (unsigned long)"uml-userspace");
/* Make sure this process dies if the kernel dies */
stub_syscall2(__NR_prctl, PR_SET_PDEATHSIG, SIGKILL);
/* read information from STDIN and close it */
res = stub_syscall3(__NR_read, 0,
(unsigned long)&init_data, sizeof(init_data));
if (res != sizeof(init_data))
stub_syscall1(__NR_exit, 10);
stub_syscall1(__NR_close, 0);
/* map stub code + data */
res = stub_syscall6(STUB_MMAP_NR,
init_data.stub_start, UM_KERN_PAGE_SIZE,
PROT_READ | PROT_EXEC, MAP_FIXED | MAP_SHARED,
init_data.stub_code_fd, init_data.stub_code_offset);
if (res != init_data.stub_start)
stub_syscall1(__NR_exit, 11);
res = stub_syscall6(STUB_MMAP_NR,
init_data.stub_start + UM_KERN_PAGE_SIZE,
STUB_DATA_PAGES * UM_KERN_PAGE_SIZE,
PROT_READ | PROT_WRITE, MAP_FIXED | MAP_SHARED,
init_data.stub_data_fd, init_data.stub_data_offset);
if (res != init_data.stub_start + UM_KERN_PAGE_SIZE)
stub_syscall1(__NR_exit, 12);
/* setup signal stack inside stub data */
stack.ss_sp = (void *)init_data.stub_start + UM_KERN_PAGE_SIZE;
stub_syscall2(__NR_sigaltstack, (unsigned long)&stack, 0);
/* register SIGSEGV handler */
sa.sa_handler_ = (void *) init_data.segv_handler;
res = stub_syscall4(__NR_rt_sigaction, SIGSEGV, (unsigned long)&sa, 0,
sizeof(sa.sa_mask));
if (res != 0)
stub_syscall1(__NR_exit, 13);
stub_syscall4(__NR_ptrace, PTRACE_TRACEME, 0, 0, 0);
stub_syscall2(__NR_kill, stub_syscall0(__NR_getpid), SIGSTOP);
stub_syscall1(__NR_exit, 14);
__builtin_unreachable();
}
__attribute__((naked)) void _start(void)
{
/*
* Since the stack after exec() starts at the top-most address,
* but that's exactly where we also want to map the stub data
* and code, this must:
* - push the stack by 1 code and STUB_DATA_PAGES data pages
* - call real_init()
* This way, real_init() can use the stack normally, while the
* original stack further down (higher address) will become
* inaccessible after the mmap() calls above.
*/
stub_start(real_init);
}
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