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linux/arch/um/kernel/skas/process.c
Bodo Stroesser 9786a8f3cb [PATCH] uml: Proper clone support for skas0 
This patch implements the clone-stub mechanism, which allows skas0 to run
with proc_mm==0, even if the clib in UML uses modify_ldt.

Note: There is a bug in skas3.v7 host patch, that avoids UML-skas from
running properly on a SMP-box.  In full skas3, I never really saw problems,
but in skas0 they showed up.

More commentary by jdike - What this patch does is makes sure that the host
parent of each new host process matches the UML parent of the corresponding
UML process.  This ensures that any changed LDTs are inherited.  This is
done by having clone actually called by the UML process from its stub,
rather than by the kernel.  We have special syscall stubs that are loaded
onto the stub code page because that code must be completely
self-contained.  These stubs are given C interfaces, and used like normal C
functions, but there are subtleties.  Principally, we have to be careful
about stack variables in stub_clone_handler after the clone.  The code is
written so that there aren't any - everything boils down to a fixed
address.  If there were any locals, references to them after the clone
would be wrong because the stack just changed.

Signed-off-by: Bodo Stroesser <bstroesser@fujitsu-siemens.com>
Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-07-07 18:23:44 -07:00

513 lines
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/*
* Copyright (C) 2002- 2004 Jeff Dike (jdike@addtoit.com)
* Licensed under the GPL
*/
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <setjmp.h>
#include <sched.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <sys/user.h>
#include <sys/time.h>
#include <asm/unistd.h>
#include <asm/types.h>
#include "user.h"
#include "ptrace_user.h"
#include "time_user.h"
#include "sysdep/ptrace.h"
#include "user_util.h"
#include "kern_util.h"
#include "skas.h"
#include "stub-data.h"
#include "mm_id.h"
#include "sysdep/sigcontext.h"
#include "sysdep/stub.h"
#include "os.h"
#include "proc_mm.h"
#include "skas_ptrace.h"
#include "chan_user.h"
#include "signal_user.h"
#include "registers.h"
#include "mem.h"
#include "uml-config.h"
#include "process.h"
int is_skas_winch(int pid, int fd, void *data)
{
if(pid != os_getpgrp())
return(0);
register_winch_irq(-1, fd, -1, data);
return(1);
}
void wait_stub_done(int pid, int sig, char * fname)
{
int n, status, err;
do {
if ( sig != -1 ) {
err = ptrace(PTRACE_CONT, pid, 0, sig);
if(err)
panic("%s : continue failed, errno = %d\n",
fname, errno);
}
sig = 0;
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
} while((n >= 0) && WIFSTOPPED(status) &&
(WSTOPSIG(status) == SIGVTALRM));
if((n < 0) || !WIFSTOPPED(status) ||
(WSTOPSIG(status) != SIGUSR1 && WSTOPSIG(status != SIGTRAP))){
panic("%s : failed to wait for SIGUSR1/SIGTRAP, "
"pid = %d, n = %d, errno = %d, status = 0x%x\n",
fname, pid, n, errno, status);
}
}
void get_skas_faultinfo(int pid, struct faultinfo * fi)
{
int err;
if(ptrace_faultinfo){
err = ptrace(PTRACE_FAULTINFO, pid, 0, fi);
if(err)
panic("get_skas_faultinfo - PTRACE_FAULTINFO failed, "
"errno = %d\n", errno);
/* Special handling for i386, which has different structs */
if (sizeof(struct ptrace_faultinfo) < sizeof(struct faultinfo))
memset((char *)fi + sizeof(struct ptrace_faultinfo), 0,
sizeof(struct faultinfo) -
sizeof(struct ptrace_faultinfo));
}
else {
wait_stub_done(pid, SIGSEGV, "get_skas_faultinfo");
/* faultinfo is prepared by the stub-segv-handler at start of
* the stub stack page. We just have to copy it.
*/
memcpy(fi, (void *)current_stub_stack(), sizeof(*fi));
}
}
static void handle_segv(int pid, union uml_pt_regs * regs)
{
get_skas_faultinfo(pid, &regs->skas.faultinfo);
segv(regs->skas.faultinfo, 0, 1, NULL);
}
/*To use the same value of using_sysemu as the caller, ask it that value (in local_using_sysemu)*/
static void handle_trap(int pid, union uml_pt_regs *regs, int local_using_sysemu)
{
int err, status;
/* Mark this as a syscall */
UPT_SYSCALL_NR(regs) = PT_SYSCALL_NR(regs->skas.regs);
if (!local_using_sysemu)
{
err = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET, __NR_getpid);
if(err < 0)
panic("handle_trap - nullifying syscall failed errno = %d\n",
errno);
err = ptrace(PTRACE_SYSCALL, pid, 0, 0);
if(err < 0)
panic("handle_trap - continuing to end of syscall failed, "
"errno = %d\n", errno);
CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
if((err < 0) || !WIFSTOPPED(status) ||
(WSTOPSIG(status) != SIGTRAP + 0x80))
panic("handle_trap - failed to wait at end of syscall, "
"errno = %d, status = %d\n", errno, status);
}
handle_syscall(regs);
}
extern int __syscall_stub_start;
static int userspace_tramp(void *stack)
{
void *addr;
ptrace(PTRACE_TRACEME, 0, 0, 0);
init_new_thread_signals(1);
enable_timer();
if(!proc_mm){
/* This has a pte, but it can't be mapped in with the usual
* tlb_flush mechanism because this is part of that mechanism
*/
int fd;
__u64 offset;
fd = phys_mapping(to_phys(&__syscall_stub_start), &offset);
addr = mmap64((void *) UML_CONFIG_STUB_CODE, page_size(),
PROT_EXEC, MAP_FIXED | MAP_PRIVATE, fd, offset);
if(addr == MAP_FAILED){
printk("mapping mmap stub failed, errno = %d\n",
errno);
exit(1);
}
if(stack != NULL){
fd = phys_mapping(to_phys(stack), &offset);
addr = mmap((void *) UML_CONFIG_STUB_DATA, page_size(),
PROT_READ | PROT_WRITE,
MAP_FIXED | MAP_SHARED, fd, offset);
if(addr == MAP_FAILED){
printk("mapping segfault stack failed, "
"errno = %d\n", errno);
exit(1);
}
}
}
if(!ptrace_faultinfo && (stack != NULL)){
unsigned long v = UML_CONFIG_STUB_CODE +
(unsigned long) stub_segv_handler -
(unsigned long) &__syscall_stub_start;
set_sigstack((void *) UML_CONFIG_STUB_DATA, page_size());
set_handler(SIGSEGV, (void *) v, SA_ONSTACK,
SIGIO, SIGWINCH, SIGALRM, SIGVTALRM,
SIGUSR1, -1);
}
os_stop_process(os_getpid());
return(0);
}
/* Each element set once, and only accessed by a single processor anyway */
#undef NR_CPUS
#define NR_CPUS 1
int userspace_pid[NR_CPUS];
int start_userspace(unsigned long stub_stack)
{
void *stack;
unsigned long sp;
int pid, status, n, flags;
stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if(stack == MAP_FAILED)
panic("start_userspace : mmap failed, errno = %d", errno);
sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
flags = CLONE_FILES | SIGCHLD;
if(proc_mm) flags |= CLONE_VM;
pid = clone(userspace_tramp, (void *) sp, flags, (void *) stub_stack);
if(pid < 0)
panic("start_userspace : clone failed, errno = %d", errno);
do {
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if(n < 0)
panic("start_userspace : wait failed, errno = %d",
errno);
} while(WIFSTOPPED(status) && (WSTOPSIG(status) == SIGVTALRM));
if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
panic("start_userspace : expected SIGSTOP, got status = %d",
status);
if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL, (void *)PTRACE_O_TRACESYSGOOD) < 0)
panic("start_userspace : PTRACE_SETOPTIONS failed, errno=%d\n",
errno);
if(munmap(stack, PAGE_SIZE) < 0)
panic("start_userspace : munmap failed, errno = %d\n", errno);
return(pid);
}
void userspace(union uml_pt_regs *regs)
{
int err, status, op, pid = userspace_pid[0];
int local_using_sysemu; /*To prevent races if using_sysemu changes under us.*/
while(1){
restore_registers(pid, regs);
/* Now we set local_using_sysemu to be used for one loop */
local_using_sysemu = get_using_sysemu();
op = SELECT_PTRACE_OPERATION(local_using_sysemu, singlestepping(NULL));
err = ptrace(op, pid, 0, 0);
if(err)
panic("userspace - could not resume userspace process, "
"pid=%d, ptrace operation = %d, errno = %d\n",
op, errno);
CATCH_EINTR(err = waitpid(pid, &status, WUNTRACED));
if(err < 0)
panic("userspace - waitpid failed, errno = %d\n",
errno);
regs->skas.is_user = 1;
save_registers(pid, regs);
UPT_SYSCALL_NR(regs) = -1; /* Assume: It's not a syscall */
if(WIFSTOPPED(status)){
switch(WSTOPSIG(status)){
case SIGSEGV:
if(PTRACE_FULL_FAULTINFO || !ptrace_faultinfo)
user_signal(SIGSEGV, regs, pid);
else handle_segv(pid, regs);
break;
case SIGTRAP + 0x80:
handle_trap(pid, regs, local_using_sysemu);
break;
case SIGTRAP:
relay_signal(SIGTRAP, regs);
break;
case SIGIO:
case SIGVTALRM:
case SIGILL:
case SIGBUS:
case SIGFPE:
case SIGWINCH:
user_signal(WSTOPSIG(status), regs, pid);
break;
default:
printk("userspace - child stopped with signal "
"%d\n", WSTOPSIG(status));
}
pid = userspace_pid[0];
interrupt_end();
/* Avoid -ERESTARTSYS handling in host */
PT_SYSCALL_NR(regs->skas.regs) = -1;
}
}
}
#define INIT_JMP_NEW_THREAD 0
#define INIT_JMP_REMOVE_SIGSTACK 1
#define INIT_JMP_CALLBACK 2
#define INIT_JMP_HALT 3
#define INIT_JMP_REBOOT 4
int copy_context_skas0(unsigned long new_stack, int pid)
{
int err;
unsigned long regs[MAX_REG_NR];
unsigned long current_stack = current_stub_stack();
struct stub_data *data = (struct stub_data *) current_stack;
struct stub_data *child_data = (struct stub_data *) new_stack;
__u64 new_offset;
int new_fd = phys_mapping(to_phys((void *)new_stack), &new_offset);
/* prepare offset and fd of child's stack as argument for parent's
* and child's mmap2 calls
*/
*data = ((struct stub_data) { .offset = MMAP_OFFSET(new_offset),
.fd = new_fd,
.timer = ((struct itimerval)
{ { 0, 1000000 / hz() },
{ 0, 1000000 / hz() }})});
get_safe_registers(regs);
/* Set parent's instruction pointer to start of clone-stub */
regs[REGS_IP_INDEX] = UML_CONFIG_STUB_CODE +
(unsigned long) stub_clone_handler -
(unsigned long) &__syscall_stub_start;
regs[REGS_SP_INDEX] = UML_CONFIG_STUB_DATA + PAGE_SIZE -
sizeof(void *);
err = ptrace_setregs(pid, regs);
if(err < 0)
panic("copy_context_skas0 : PTRACE_SETREGS failed, "
"pid = %d, errno = %d\n", pid, errno);
/* set a well known return code for detection of child write failure */
child_data->err = 12345678;
/* Wait, until parent has finished its work: read child's pid from
* parent's stack, and check, if bad result.
*/
wait_stub_done(pid, 0, "copy_context_skas0");
pid = data->err;
if(pid < 0)
panic("copy_context_skas0 - stub-parent reports error %d\n",
pid);
/* Wait, until child has finished too: read child's result from
* child's stack and check it.
*/
wait_stub_done(pid, -1, "copy_context_skas0");
if (child_data->err != UML_CONFIG_STUB_DATA)
panic("copy_context_skas0 - stub-child reports error %d\n",
child_data->err);
if (ptrace(PTRACE_OLDSETOPTIONS, pid, NULL,
(void *)PTRACE_O_TRACESYSGOOD) < 0)
panic("copy_context_skas0 : PTRACE_SETOPTIONS failed, "
"errno = %d\n", errno);
return pid;
}
void new_thread(void *stack, void **switch_buf_ptr, void **fork_buf_ptr,
void (*handler)(int))
{
unsigned long flags;
sigjmp_buf switch_buf, fork_buf;
*switch_buf_ptr = &switch_buf;
*fork_buf_ptr = &fork_buf;
/* Somewhat subtle - siglongjmp restores the signal mask before doing
* the longjmp. This means that when jumping from one stack to another
* when the target stack has interrupts enabled, an interrupt may occur
* on the source stack. This is bad when starting up a process because
* it's not supposed to get timer ticks until it has been scheduled.
* So, we disable interrupts around the sigsetjmp to ensure that
* they can't happen until we get back here where they are safe.
*/
flags = get_signals();
block_signals();
if(sigsetjmp(fork_buf, 1) == 0)
new_thread_proc(stack, handler);
remove_sigstack();
set_signals(flags);
}
void thread_wait(void *sw, void *fb)
{
sigjmp_buf buf, **switch_buf = sw, *fork_buf;
*switch_buf = &buf;
fork_buf = fb;
if(sigsetjmp(buf, 1) == 0)
siglongjmp(*fork_buf, INIT_JMP_REMOVE_SIGSTACK);
}
void switch_threads(void *me, void *next)
{
sigjmp_buf my_buf, **me_ptr = me, *next_buf = next;
*me_ptr = &my_buf;
if(sigsetjmp(my_buf, 1) == 0)
siglongjmp(*next_buf, 1);
}
static sigjmp_buf initial_jmpbuf;
/* XXX Make these percpu */
static void (*cb_proc)(void *arg);
static void *cb_arg;
static sigjmp_buf *cb_back;
int start_idle_thread(void *stack, void *switch_buf_ptr, void **fork_buf_ptr)
{
sigjmp_buf **switch_buf = switch_buf_ptr;
int n;
set_handler(SIGWINCH, (__sighandler_t) sig_handler,
SA_ONSTACK | SA_RESTART, SIGUSR1, SIGIO, SIGALRM,
SIGVTALRM, -1);
*fork_buf_ptr = &initial_jmpbuf;
n = sigsetjmp(initial_jmpbuf, 1);
switch(n){
case INIT_JMP_NEW_THREAD:
new_thread_proc((void *) stack, new_thread_handler);
break;
case INIT_JMP_REMOVE_SIGSTACK:
remove_sigstack();
break;
case INIT_JMP_CALLBACK:
(*cb_proc)(cb_arg);
siglongjmp(*cb_back, 1);
break;
case INIT_JMP_HALT:
kmalloc_ok = 0;
return(0);
case INIT_JMP_REBOOT:
kmalloc_ok = 0;
return(1);
default:
panic("Bad sigsetjmp return in start_idle_thread - %d\n", n);
}
siglongjmp(**switch_buf, 1);
}
void remove_sigstack(void)
{
stack_t stack = ((stack_t) { .ss_flags = SS_DISABLE,
.ss_sp = NULL,
.ss_size = 0 });
if(sigaltstack(&stack, NULL) != 0)
panic("disabling signal stack failed, errno = %d\n", errno);
}
void initial_thread_cb_skas(void (*proc)(void *), void *arg)
{
sigjmp_buf here;
cb_proc = proc;
cb_arg = arg;
cb_back = &here;
block_signals();
if(sigsetjmp(here, 1) == 0)
siglongjmp(initial_jmpbuf, INIT_JMP_CALLBACK);
unblock_signals();
cb_proc = NULL;
cb_arg = NULL;
cb_back = NULL;
}
void halt_skas(void)
{
block_signals();
siglongjmp(initial_jmpbuf, INIT_JMP_HALT);
}
void reboot_skas(void)
{
block_signals();
siglongjmp(initial_jmpbuf, INIT_JMP_REBOOT);
}
void switch_mm_skas(struct mm_id *mm_idp)
{
int err;
#warning need cpu pid in switch_mm_skas
if(proc_mm){
err = ptrace(PTRACE_SWITCH_MM, userspace_pid[0], 0,
mm_idp->u.mm_fd);
if(err)
panic("switch_mm_skas - PTRACE_SWITCH_MM failed, "
"errno = %d\n", errno);
}
else userspace_pid[0] = mm_idp->u.pid;
}
/*
* Overrides for Emacs so that we follow Linus's tabbing style.
* Emacs will notice this stuff at the end of the file and automatically
* adjust the settings for this buffer only. This must remain at the end
* of the file.
* ---------------------------------------------------------------------------
* Local variables:
* c-file-style: "linux"
* End:
*/
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