static int ptrace_child(void *arg)
{
- int pid = os_getpid();
+ 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);
- _exit(os_getpid() == 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)
return(pid);
}
-static void stop_ptraced_child(int pid, void *stack, int exitcode)
+/* 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;
+ 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))
- panic("check_ptrace : child exited with status 0x%x", status);
+ 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;
" 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");
+ " See http://perso.wanadoo.fr/laurent.vivier/UML/ for further information.\n\n");
static void __init check_sysemu(void)
{
void *stack;
int pid, n, status;
- if (mode_tt)
- return;
-
printk("Checking syscall emulation patch for ptrace...");
sysemu_supported = 0;
pid = start_ptraced_child(&stack);
- if(ptrace(PTRACE_SYSEMU, pid, 0, 0) >= 0) {
- struct user_regs_struct regs;
- 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, "
- "got status = %d", status);
+ if(ptrace(PTRACE_SYSEMU, pid, 0, 0) < 0)
+ goto fail;
- if (ptrace(PTRACE_GETREGS, pid, 0, ®s) < 0)
- panic("check_ptrace : failed to read child "
- "registers, errno = %d", errno);
- regs.orig_eax = pid;
- if (ptrace(PTRACE_SETREGS, pid, 0, ®s) < 0)
- panic("check_ptrace : failed to modify child "
- "registers, errno = %d", errno);
+ 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_POKEUSER, pid, PT_SYSCALL_RET_OFFSET,
+ os_getpid());
+ if(n < 0)
+ panic("check_sysemu : failed to modify system "
+ "call return, errno = %d", errno);
- stop_ptraced_child(pid, stack, 0);
-
- sysemu_supported = 1;
- printk("found\n");
- }
- else
- {
- stop_ptraced_child(pid, stack, 1);
- sysemu_supported = 0;
- printk("missing\n");
- }
+ if (stop_ptraced_child(pid, stack, 0, 0) < 0)
+ goto fail_stopped;
+ sysemu_supported = 1;
+ printk("OK\n");
set_using_sysemu(!force_sysemu_disabled);
+ return;
+
+fail:
+ stop_ptraced_child(pid, stack, 1, 0);
+fail_stopped:
+ sysemu_supported = 0;
+ printk("missing\n");
}
void __init check_ptrace(void)
break;
}
}
- stop_ptraced_child(pid, stack, 0);
+ stop_ptraced_child(pid, stack, 0, 1);
printk("OK\n");
check_sysemu();
}
else printf("found\n");
init_registers(pid);
- stop_ptraced_child(pid, stack, 1);
+ stop_ptraced_child(pid, stack, 1, 1);
printf("Checking for /proc/mm...");
if(os_access("/proc/mm", OS_ACC_W_OK) < 0){
git://git.onelab.eu / linux-2.6.git / blobdiff