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linux/arch/um/kernel/process.c
Jeff Dike cd2ee4a30c [PATCH] uml: Fix SIGWINCH relaying 
This makes SIGWINCH work again, and fixes a couple of SIGWINCH-associated
crashes.  First, the sigio thread disables SIGWINCH because all hell breaks
loose if it ever gets one and tries to call the signal handling code.  Second,
there was a problem with deferencing tty structs after they were freed.  The
SIGWINCH support for a tty wasn't being turned off or freed after the tty went
away.

Signed-off-by: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-05-05 16:36:36 -07:00

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/*
* Copyright (C) 2000, 2001, 2002 Jeff Dike (jdike@karaya.com)
* Licensed under the GPL
*/
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <sched.h>
#include <errno.h>
#include <stdarg.h>
#include <stdlib.h>
#include <setjmp.h>
#include <sys/time.h>
#include <sys/wait.h>
#include <sys/mman.h>
#include <asm/unistd.h>
#include <asm/page.h>
#include "user_util.h"
#include "kern_util.h"
#include "user.h"
#include "process.h"
#include "signal_kern.h"
#include "signal_user.h"
#include "sysdep/ptrace.h"
#include "sysdep/sigcontext.h"
#include "irq_user.h"
#include "ptrace_user.h"
#include "time_user.h"
#include "init.h"
#include "os.h"
#include "uml-config.h"
#include "ptrace_user.h"
#include "choose-mode.h"
#include "mode.h"
#ifdef UML_CONFIG_MODE_SKAS
#include "skas.h"
#include "skas_ptrace.h"
#include "registers.h"
#endif
void init_new_thread_stack(void *sig_stack, void (*usr1_handler)(int))
{
int flags = 0, pages;
if(sig_stack != NULL){
pages = (1 << UML_CONFIG_KERNEL_STACK_ORDER);
set_sigstack(sig_stack, pages * page_size());
flags = SA_ONSTACK;
}
if(usr1_handler) set_handler(SIGUSR1, usr1_handler, flags, -1);
}
void init_new_thread_signals(int altstack)
{
int flags = altstack ? SA_ONSTACK : 0;
set_handler(SIGSEGV, (__sighandler_t) sig_handler, flags,
SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
set_handler(SIGTRAP, (__sighandler_t) sig_handler, flags,
SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
set_handler(SIGFPE, (__sighandler_t) sig_handler, flags,
SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
set_handler(SIGILL, (__sighandler_t) sig_handler, flags,
SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
set_handler(SIGBUS, (__sighandler_t) sig_handler, flags,
SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
set_handler(SIGUSR2, (__sighandler_t) sig_handler,
flags, SIGUSR1, SIGIO, SIGWINCH, SIGALRM, SIGVTALRM, -1);
signal(SIGHUP, SIG_IGN);
init_irq_signals(altstack);
}
struct tramp {
int (*tramp)(void *);
void *tramp_data;
unsigned long temp_stack;
int flags;
int pid;
};
/* See above for why sigkill is here */
int sigkill = SIGKILL;
int outer_tramp(void *arg)
{
struct tramp *t;
int sig = sigkill;
t = arg;
t->pid = clone(t->tramp, (void *) t->temp_stack + page_size()/2,
t->flags, t->tramp_data);
if(t->pid > 0) wait_for_stop(t->pid, SIGSTOP, PTRACE_CONT, NULL);
kill(os_getpid(), sig);
_exit(0);
}
int start_fork_tramp(void *thread_arg, unsigned long temp_stack,
int clone_flags, int (*tramp)(void *))
{
struct tramp arg;
unsigned long sp;
int new_pid, status, err;
/* The trampoline will run on the temporary stack */
sp = stack_sp(temp_stack);
clone_flags |= CLONE_FILES | SIGCHLD;
arg.tramp = tramp;
arg.tramp_data = thread_arg;
arg.temp_stack = temp_stack;
arg.flags = clone_flags;
/* Start the process and wait for it to kill itself */
new_pid = clone(outer_tramp, (void *) sp, clone_flags, &arg);
if(new_pid < 0)
return(new_pid);
CATCH_EINTR(err = waitpid(new_pid, &status, 0));
if(err < 0)
panic("Waiting for outer trampoline failed - errno = %d",
errno);
if(!WIFSIGNALED(status) || (WTERMSIG(status) != SIGKILL))
panic("outer trampoline didn't exit with SIGKILL, "
"status = %d", status);
return(arg.pid);
}
static int ptrace_child(void *arg)
{
int ret;
int pid = os_getpid(), ppid = getppid();
int sc_result;
if(ptrace(PTRACE_TRACEME, 0, 0, 0) < 0){
perror("ptrace");
os_kill_process(pid, 0);
}
os_stop_process(pid);
/*This syscall will be intercepted by the parent. Don't call more than
* once, please.*/
sc_result = os_getpid();
if (sc_result == pid)
ret = 1; /*Nothing modified by the parent, we are running
normally.*/
else if (sc_result == ppid)
ret = 0; /*Expected in check_ptrace and check_sysemu when they
succeed in modifying the stack frame*/
else
ret = 2; /*Serious trouble! This could be caused by a bug in
host 2.6 SKAS3/2.6 patch before release -V6, together
with a bug in the UML code itself.*/
_exit(ret);
}
static int start_ptraced_child(void **stack_out)
{
void *stack;
unsigned long sp;
int pid, n, status;
stack = mmap(NULL, PAGE_SIZE, PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if(stack == MAP_FAILED)
panic("check_ptrace : mmap failed, errno = %d", errno);
sp = (unsigned long) stack + PAGE_SIZE - sizeof(void *);
pid = clone(ptrace_child, (void *) sp, SIGCHLD, NULL);
if(pid < 0)
panic("check_ptrace : clone failed, errno = %d", errno);
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if(n < 0)
panic("check_ptrace : wait failed, errno = %d", errno);
if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGSTOP))
panic("check_ptrace : expected SIGSTOP, got status = %d",
status);
*stack_out = stack;
return(pid);
}
/* When testing for SYSEMU support, if it is one of the broken versions, we must
* just avoid using sysemu, not panic, but only if SYSEMU features are broken.
* So only for SYSEMU features we test mustpanic, while normal host features
* must work anyway!*/
static int stop_ptraced_child(int pid, void *stack, int exitcode, int mustpanic)
{
int status, n, ret = 0;
if(ptrace(PTRACE_CONT, pid, 0, 0) < 0)
panic("check_ptrace : ptrace failed, errno = %d", errno);
CATCH_EINTR(n = waitpid(pid, &status, 0));
if(!WIFEXITED(status) || (WEXITSTATUS(status) != exitcode)) {
int exit_with = WEXITSTATUS(status);
if (exit_with == 2)
printk("check_ptrace : child exited with status 2. "
"Serious trouble happening! Try updating your "
"host skas patch!\nDisabling SYSEMU support.");
printk("check_ptrace : child exited with exitcode %d, while "
"expecting %d; status 0x%x", exit_with,
exitcode, status);
if (mustpanic)
panic("\n");
else
printk("\n");
ret = -1;
}
if(munmap(stack, PAGE_SIZE) < 0)
panic("check_ptrace : munmap failed, errno = %d", errno);
return ret;
}
static int force_sysemu_disabled = 0;
static int __init nosysemu_cmd_param(char *str, int* add)
{
force_sysemu_disabled = 1;
return 0;
}
__uml_setup("nosysemu", nosysemu_cmd_param,
"nosysemu\n"
" Turns off syscall emulation patch for ptrace (SYSEMU) on.\n"
" SYSEMU is a performance-patch introduced by Laurent Vivier. It changes\n"
" behaviour of ptrace() and helps reducing host context switch rate.\n"
" To make it working, you need a kernel patch for your host, too.\n"
" See http://perso.wanadoo.fr/laurent.vivier/UML/ for further information.\n\n");
static void __init check_sysemu(void)
{
void *stack;
int pid, syscall, n, status, count=0;
printk("Checking syscall emulation patch for ptrace...");
sysemu_supported = 0;
pid = start_ptraced_child(&stack);
if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
goto fail;
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if (n < 0)
panic("check_sysemu : wait failed, errno = %d", errno);
if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
panic("check_sysemu : expected SIGTRAP, "
"got status = %d", status);
n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
os_getpid());
if(n < 0)
panic("check_sysemu : failed to modify system "
"call return, errno = %d", errno);
if (stop_ptraced_child(pid, stack, 0, 0) < 0)
goto fail_stopped;
sysemu_supported = 1;
printk("OK\n");
set_using_sysemu(!force_sysemu_disabled);
printk("Checking advanced syscall emulation patch for ptrace...");
pid = start_ptraced_child(&stack);
while(1){
count++;
if(ptrace(PTRACE_SYSEMU_SINGLESTEP, pid, 0, 0) < 0)
goto fail;
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if(n < 0)
panic("check_ptrace : wait failed, errno = %d", errno);
if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP))
panic("check_ptrace : expected (SIGTRAP|SYSCALL_TRAP), "
"got status = %d", status);
syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
0);
if(syscall == __NR_getpid){
if (!count)
panic("check_ptrace : SYSEMU_SINGLESTEP doesn't singlestep");
n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_RET_OFFSET,
os_getpid());
if(n < 0)
panic("check_sysemu : failed to modify system "
"call return, errno = %d", errno);
break;
}
}
if (stop_ptraced_child(pid, stack, 0, 0) < 0)
goto fail_stopped;
sysemu_supported = 2;
printk("OK\n");
if ( !force_sysemu_disabled )
set_using_sysemu(sysemu_supported);
return;
fail:
stop_ptraced_child(pid, stack, 1, 0);
fail_stopped:
printk("missing\n");
}
void __init check_ptrace(void)
{
void *stack;
int pid, syscall, n, status;
printk("Checking that ptrace can change system call numbers...");
pid = start_ptraced_child(&stack);
if (ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)PTRACE_O_TRACESYSGOOD) < 0)
panic("check_ptrace: PTRACE_SETOPTIONS failed, errno = %d", errno);
while(1){
if(ptrace(PTRACE_SYSCALL, pid, 0, 0) < 0)
panic("check_ptrace : ptrace failed, errno = %d",
errno);
CATCH_EINTR(n = waitpid(pid, &status, WUNTRACED));
if(n < 0)
panic("check_ptrace : wait failed, errno = %d", errno);
if(!WIFSTOPPED(status) || (WSTOPSIG(status) != SIGTRAP + 0x80))
panic("check_ptrace : expected SIGTRAP + 0x80, "
"got status = %d", status);
syscall = ptrace(PTRACE_PEEKUSR, pid, PT_SYSCALL_NR_OFFSET,
0);
if(syscall == __NR_getpid){
n = ptrace(PTRACE_POKEUSR, pid, PT_SYSCALL_NR_OFFSET,
__NR_getppid);
if(n < 0)
panic("check_ptrace : failed to modify system "
"call, errno = %d", errno);
break;
}
}
stop_ptraced_child(pid, stack, 0, 1);
printk("OK\n");
check_sysemu();
}
int run_kernel_thread(int (*fn)(void *), void *arg, void **jmp_ptr)
{
sigjmp_buf buf;
int n;
*jmp_ptr = &buf;
n = sigsetjmp(buf, 1);
if(n != 0)
return(n);
(*fn)(arg);
return(0);
}
void forward_pending_sigio(int target)
{
sigset_t sigs;
if(sigpending(&sigs))
panic("forward_pending_sigio : sigpending failed");
if(sigismember(&sigs, SIGIO))
kill(target, SIGIO);
}
#ifdef UML_CONFIG_MODE_SKAS
static inline int check_skas3_ptrace_support(void)
{
struct ptrace_faultinfo fi;
void *stack;
int pid, n, ret = 1;
printf("Checking for the skas3 patch in the host...");
pid = start_ptraced_child(&stack);
n = ptrace(PTRACE_FAULTINFO, pid, 0, &fi);
if (n < 0) {
if(errno == EIO)
printf("not found\n");
else {
perror("not found");
}
ret = 0;
} else {
printf("found\n");
}
init_registers(pid);
stop_ptraced_child(pid, stack, 1, 1);
return(ret);
}
int can_do_skas(void)
{
int ret = 1;
printf("Checking for /proc/mm...");
if (os_access("/proc/mm", OS_ACC_W_OK) < 0) {
printf("not found\n");
ret = 0;
goto out;
} else {
printf("found\n");
}
ret = check_skas3_ptrace_support();
out:
return ret;
}
#else
int can_do_skas(void)
{
return(0);
}
#endif
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