arch/um/sys-x86_64/stub_segv.c

   1 /*
   2  * Copyright (C) 2004 Jeff Dike (jdike@addtoit.com)
   3  * Licensed under the GPL
   4  */
   5
   6 #include <stddef.h>
   7 #include <signal.h>
   8 #include <asm/unistd.h>
   9 #include "uml-config.h"
  10 #include "sysdep/sigcontext.h"
  11 #include "sysdep/faultinfo.h"
  12 #include "sysdep/stub.h"
  13
  14 /* Copied from sys-x86_64/signal.c - Can't find an equivalent definition
  15  * in the libc headers anywhere.
  16  */
  17 struct rt_sigframe
  18 {
  19         char *pretcode;
  20         struct ucontext uc;
  21         struct siginfo info;
  22 };
  23
  24 /* Copied here from <linux/kernel.h> - we're userspace. */
  25 #define container_of(ptr, type, member) ({                   \
  26         const typeof( ((type *)0)->member ) *__mptr = (ptr); \
  27         (type *)( (char *)__mptr - offsetof(type,member) );})
  28
  29 void __attribute__ ((__section__ (".__syscall_stub")))
  30 stub_segv_handler(int sig)
  31 {
  32         struct ucontext *uc;
  33         int pid;
  34
  35         __asm__ __volatile__("movq %%rdx, %0" : "=g" (uc) :);
  36         GET_FAULTINFO_FROM_SC(*((struct faultinfo *) UML_CONFIG_STUB_DATA),
  37                               &uc->uc_mcontext);
  38
  39         pid = stub_syscall0(__NR_getpid);
  40         stub_syscall2(__NR_kill, pid, SIGUSR1);
  41
  42         /* sys_sigreturn expects that the stack pointer will be 8 bytes into
  43          * the signal frame.  So, we use the ucontext pointer, which we know
  44          * already, to get the signal frame pointer, and add 8 to that.
  45          */
  46         __asm__ __volatile__("movq %0, %%rsp; movq %1, %%rax ; syscall": :
  47                              "g" ((unsigned long)
  48                                   container_of(uc, struct rt_sigframe, uc) + 8),
  49                              "g" (__NR_rt_sigreturn));
  50 }