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 "as-layout.h"
  10 #include "uml-config.h"
  11 #include "sysdep/sigcontext.h"
  12 #include "sysdep/faultinfo.h"
  13 #include "sysdep/stub.h"
  14
  15 /* Copied from sys-x86_64/signal.c - Can't find an equivalent definition
  16  * in the libc headers anywhere.
  17  */
  18 struct rt_sigframe
  19 {
  20         char *pretcode;
  21         struct ucontext uc;
  22         struct siginfo info;
  23 };
  24
  25 /* Copied here from <linux/kernel.h> - we're userspace. */
  26 #define container_of(ptr, type, member) ({                   \
  27         const typeof( ((type *)0)->member ) *__mptr = (ptr); \
  28         (type *)( (char *)__mptr - offsetof(type,member) );})
  29
  30 void __attribute__ ((__section__ (".__syscall_stub")))
  31 stub_segv_handler(int sig)
  32 {
  33         struct ucontext *uc;
  34         int pid;
  35
  36         __asm__ __volatile__("movq %%rdx, %0" : "=g" (uc) :);
  37         GET_FAULTINFO_FROM_SC(*((struct faultinfo *) STUB_DATA),
  38                               &uc->uc_mcontext);
  39
  40         pid = stub_syscall0(__NR_getpid);
  41         stub_syscall2(__NR_kill, pid, SIGUSR1);
  42
  43         /* sys_sigreturn expects that the stack pointer will be 8 bytes into
  44          * the signal frame.  So, we use the ucontext pointer, which we know
  45          * already, to get the signal frame pointer, and add 8 to that.
  46          */
  47         __asm__ __volatile__("movq %0, %%rsp; movq %1, %%rax ; syscall": :
  48                              "g" ((unsigned long)
  49                                   container_of(uc, struct rt_sigframe, uc) + 8),
  50                              "g" (__NR_rt_sigreturn));
  51 }