Alexandre Oliva writes:

This patch adds code to uClibc to support a new ABI designed for the
FR-V architecture, that enables text segments of executables and
shared libraries to be shared by multiple processes on an OS such as
uClinux, that can run on FR-V processors without an MMU.

Patches for binutils and GCC have just been posted in the
corresponding mailing lists.  The binutils patch was approved,
but there's one additional patch pending review, that I posted
this week.  An updated GCC patch will be posted to
gcc-patches@gcc.gnu.org as soon as I complete testing (I used a
known-good compiler to test the uClibc patch below).

Since the existing dynamic loader code didn't support independent
relocation of segments, it required changes that were somewhat
extensive.  I've added a number of new machine-specific macros to try
to keep the platform and ABI-specific details outside the generic
code.  I hope this is not a problem.

3 files changed, 715 insertions, 0 deletions

diff --git a/libc/sysdeps/linux/frv/sys/procfs.h b/libc/sysdeps/linux/frv/sys/procfs.h
new file mode 100644
index 000000000..f07523342
--- /dev/null
+++ b/libc/sysdeps/linux/frv/sys/procfs.h
@@ -0,0 +1,125 @@
+/* Copyright (C) 1996, 1997, 1999, 2000, 2003 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#ifndef _SYS_PROCFS_H
+#define _SYS_PROCFS_H	1
+
+/* This is somewhat modelled after the file of the same name on SVR4
+   systems.  It provides a definition of the core file format for ELF
+   used on Linux.  It doesn't have anything to do with the /proc file
+   system, even though Linux has one.
+
+   Anyway, the whole purpose of this file is for GDB and GDB only.
+   Don't read too much into it.  Don't use it for anything other than
+   GDB unless you know what you are doing.  */
+
+#include <features.h>
+#include <sys/time.h>
+#include <sys/types.h>
+#include <sys/user.h>
+
+__BEGIN_DECLS
+
+/* Type for a general-purpose register.  */
+typedef unsigned long elf_greg_t;
+
+/* And the whole bunch of them.  We could have used `struct
+   user_regs_struct' directly in the typedef, but tradition says that
+   the register set is an array, which does have some peculiar
+   semantics, so leave it that way.  */
+#define ELF_NGREG (sizeof (struct user_int_regs) / sizeof(elf_greg_t))
+typedef elf_greg_t elf_gregset_t[ELF_NGREG];
+
+/* Register set for the floating-point registers.  */
+typedef struct user_fpmedia_regs elf_fpregset_t;
+
+/* Signal info.  */
+struct elf_siginfo
+  {
+    int si_signo;			/* Signal number.  */
+    int si_code;			/* Extra code.  */
+    int si_errno;			/* Errno.  */
+  };
+
+
+/* Definitions to generate Intel SVR4-like core files.  These mostly
+   have the same names as the SVR4 types with "elf_" tacked on the
+   front to prevent clashes with Linux definitions, and the typedef
+   forms have been avoided.  This is mostly like the SVR4 structure,
+   but more Linuxy, with things that Linux does not support and which
+   GDB doesn't really use excluded.  */
+
+struct elf_prstatus
+  {
+    struct elf_siginfo pr_info;		/* Info associated with signal.  */
+    short int pr_cursig;		/* Current signal.  */
+    unsigned long int pr_sigpend;	/* Set of pending signals.  */
+    unsigned long int pr_sighold;	/* Set of held signals.  */
+    __pid_t pr_pid;
+    __pid_t pr_ppid;
+    __pid_t pr_pgrp;
+    __pid_t pr_sid;
+    struct timeval pr_utime;		/* User time.  */
+    struct timeval pr_stime;		/* System time.  */
+    struct timeval pr_cutime;		/* Cumulative user time.  */
+    struct timeval pr_cstime;		/* Cumulative system time.  */
+    elf_gregset_t pr_reg;		/* GP registers.  */
+    int pr_fpvalid;			/* True if math copro being used.  */
+  };
+
+
+#define ELF_PRARGSZ     (80)    /* Number of chars for args.  */
+
+struct elf_prpsinfo
+  {
+    char pr_state;			/* Numeric process state.  */
+    char pr_sname;			/* Char for pr_state.  */
+    char pr_zomb;			/* Zombie.  */
+    char pr_nice;			/* Nice val.  */
+    unsigned long int pr_flag;		/* Flags.  */
+    unsigned short int pr_uid;
+    unsigned short int pr_gid;
+    int pr_pid, pr_ppid, pr_pgrp, pr_sid;
+    /* Lots missing */
+    char pr_fname[16];			/* Filename of executable.  */
+    char pr_psargs[ELF_PRARGSZ];	/* Initial part of arg list.  */
+  };
+
+
+/* The rest of this file provides the types for emulation of the
+   Solaris <proc_service.h> interfaces that should be implemented by
+   users of libthread_db.  */
+
+/* Addresses.  */
+typedef void *psaddr_t;
+
+/* Register sets.  Linux has different names.  */
+typedef elf_gregset_t prgregset_t;
+typedef elf_fpregset_t prfpregset_t;
+
+/* We don't have any differences between processes and threads,
+   therefore have only one PID type.  */
+typedef __pid_t lwpid_t;
+
+/* Process status and info.  In the end we do provide typedefs for them.  */
+typedef struct elf_prstatus prstatus_t;
+typedef struct elf_prpsinfo prpsinfo_t;
+
+__END_DECLS
+
+#endif	/* sys/procfs.h */
diff --git a/libc/sysdeps/linux/frv/sys/ptrace.h b/libc/sysdeps/linux/frv/sys/ptrace.h
new file mode 100644
index 000000000..6b0eca7b0
--- /dev/null
+++ b/libc/sysdeps/linux/frv/sys/ptrace.h
@@ -0,0 +1,139 @@
+/* `ptrace' debugger support interface.  FRV-Linux version.
+   Copyright (C) 1996, 1997, 1998, 1999, 2000, 2004
+   Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#ifndef _SYS_PTRACE_H
+#define _SYS_PTRACE_H	1
+
+#include <features.h>
+
+__BEGIN_DECLS
+
+/* Type of the REQUEST argument to `ptrace.'  */
+enum __ptrace_request
+{
+  /* Indicate that the process making this request should be traced.
+     All signals received by this process can be intercepted by its
+     parent, and its parent can use the other `ptrace' requests.  */
+  PTRACE_TRACEME = 0,
+#define PT_TRACE_ME PTRACE_TRACEME
+
+  /* Return the word in the process's text space at address ADDR.  */
+  PTRACE_PEEKTEXT = 1,
+#define PT_READ_I PTRACE_PEEKTEXT
+
+  /* Return the word in the process's data space at address ADDR.  */
+  PTRACE_PEEKDATA = 2,
+#define PT_READ_D PTRACE_PEEKDATA
+
+  /* Return the word in the process's user area at offset ADDR.  */
+  PTRACE_PEEKUSER = 3,
+#define PT_READ_U PTRACE_PEEKUSER
+
+  /* Write the word DATA into the process's text space at address ADDR.  */
+  PTRACE_POKETEXT = 4,
+#define PT_WRITE_I PTRACE_POKETEXT
+
+  /* Write the word DATA into the process's data space at address ADDR.  */
+  PTRACE_POKEDATA = 5,
+#define PT_WRITE_D PTRACE_POKEDATA
+
+  /* Write the word DATA into the process's user area at offset ADDR.  */
+  PTRACE_POKEUSER = 6,
+#define PT_WRITE_U PTRACE_POKEUSER
+
+  /* Continue the process.  */
+  PTRACE_CONT = 7,
+#define PT_CONTINUE PTRACE_CONT
+
+  /* Kill the process.  */
+  PTRACE_KILL = 8,
+#define PT_KILL PTRACE_KILL
+
+  /* Single step the process.
+     This is not supported on all machines.  */
+  PTRACE_SINGLESTEP = 9,
+#define PT_STEP PTRACE_SINGLESTEP
+
+  /* Get all general purpose registers used by a processes.
+     This is not supported on all machines.  */
+   PTRACE_GETREGS = 12,
+#define PT_GETREGS PTRACE_GETREGS
+
+  /* Set all general purpose registers used by a processes.
+     This is not supported on all machines.  */
+   PTRACE_SETREGS = 13,
+#define PT_SETREGS PTRACE_SETREGS
+
+  /* Get all floating point registers used by a processes.
+     This is not supported on all machines.  */
+   PTRACE_GETFPREGS = 14,
+#define PT_GETFPREGS PTRACE_GETFPREGS
+
+  /* Set all floating point registers used by a processes.
+     This is not supported on all machines.  */
+   PTRACE_SETFPREGS = 15,
+#define PT_SETFPREGS PTRACE_SETFPREGS
+
+  /* Attach to a process that is already running. */
+  PTRACE_ATTACH = 16,
+#define PT_ATTACH PTRACE_ATTACH
+
+  /* Detach from a process attached to with PTRACE_ATTACH.  */
+  PTRACE_DETACH = 17,
+#define PT_DETACH PTRACE_DETACH
+
+  /* Get all extended floating point registers used by a processes.
+     This is not supported on all machines.  */
+   PTRACE_GETFPXREGS = 18,
+#define PT_GETFPXREGS PTRACE_GETFPXREGS
+
+  /* Set all extended floating point registers used by a processes.
+     This is not supported on all machines.  */
+   PTRACE_SETFPXREGS = 19,
+#define PT_SETFPXREGS PTRACE_SETFPXREGS
+
+  /* Continue and stop at the next (return from) syscall.  */
+  PTRACE_SYSCALL = 24,
+#define PT_SYSCALL PTRACE_SYSCALL
+
+  /* Obtain the load map of the main program or the interpreter of the
+     ptraced process, depending on whether the addr argument is
+     (void*)0 or (void*)1, respectively.  */
+  PTRACE_GETFDPIC = 31
+#define PT_GETFDPIC PTRACE_GETFDPIC
+};
+
+#define PTRACE_GETFDPIC_EXEC      ((void*)0)	/* [addr] request the executable loadmap */
+#define PTRACE_GETFDPIC_INTERP    ((void*)1)	/* [addr] request the interpreter loadmap */
+
+/* Perform process tracing functions.  REQUEST is one of the values
+   above, and determines the action to be taken.
+   For all requests except PTRACE_TRACEME, PID specifies the process to be
+   traced.
+
+   PID and the other arguments described above for the various requests should
+   appear (those that are used for the particular request) as:
+     pid_t PID, void *ADDR, int DATA, void *ADDR2
+   after REQUEST.  */
+extern long int ptrace (enum __ptrace_request __request, ...) __THROW;
+
+__END_DECLS
+
+#endif /* _SYS_PTRACE_H */
diff --git a/libc/sysdeps/linux/frv/sys/ucontext.h b/libc/sysdeps/linux/frv/sys/ucontext.h
new file mode 100644
index 000000000..2385a072e
--- /dev/null
+++ b/libc/sysdeps/linux/frv/sys/ucontext.h
@@ -0,0 +1,451 @@
+/* Copyright (C) 1999, 2000, 2001, 2003 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Library General Public License as
+   published by the Free Software Foundation; either version 2 of the
+   License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Library General Public License for more details.
+
+   You should have received a copy of the GNU Library General Public
+   License along with the GNU C Library; see the file COPYING.LIB.  If not,
+   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+   Boston, MA 02111-1307, USA.  */
+
+#ifndef _SYS_UCONTEXT_H
+#define _SYS_UCONTEXT_H	1
+
+#include <features.h>
+#include <signal.h>
+
+/* We need the signal context definitions even if they are not used
+   included in <signal.h>.  */
+#include <bits/sigcontext.h>
+
+
+typedef unsigned long greg_t;
+
+/* Number of general registers.  */
+#define NGREG	(10+2+64)
+
+/* Container for all general registers.  */
+typedef greg_t gregset_t[NGREG];
+
+#ifdef __USE_GNU
+/* Number of each register is the `gregset_t' array.  */
+enum
+{
+  PSR = 0,
+#define PSR	PSR
+  ISR = 1,
+#define ISR	ISR
+  CCR = 2,
+#define CCR	CCR
+  CCCR = 3,
+#define CCCR	CCCR
+  LR = 4,
+#define LR	LR
+  LCR = 5,
+#define LCR	LCR
+  PC = 6,
+#define PC	PC
+  __STATUS = 7,
+#define __STATUS	__STATUS
+  SYSCALLNO = 8,
+#define SYSCALLNO	SYSCALLNO
+  ORIG_GR8 = 9,
+#define ORIG_GR8	ORIG_GR8
+  GNER0 = 10,
+#define GNER0	GNER0
+  GNER1 = 11,
+#define GNER1	GNER1
+  GR0 = 12,
+#define GR0	GR0
+  GR1 = 13,
+#define GR1	GR1
+  GR2 = 14,
+#define GR2	GR2
+  GR3 = 15,
+#define GR3	GR3
+  GR4 = 16,
+#define GR4	GR4
+  GR5 = 17,
+#define GR5	GR5
+  GR6 = 18,
+#define GR6	GR6
+  GR7 = 19,
+#define GR7	GR7
+  GR8 = 20,
+#define GR8	GR8
+  GR9 = 21,
+#define GR9	GR9
+  GR10 = 22,
+#define GR10	GR10
+  GR11 = 23,
+#define GR11	GR11
+  GR12 = 24,
+#define GR12	GR12
+  GR13 = 25,
+#define GR13	GR13
+  GR14 = 26,
+#define GR14	GR14
+  GR15 = 27,
+#define GR15	GR15
+  GR16 = 28,
+#define GR16	GR16
+  GR17 = 29,
+#define GR17	GR17
+  GR18 = 30,
+#define GR18	GR18
+  GR19 = 31,
+#define GR19	GR19
+  GR20 = 32,
+#define GR20	GR20
+  GR21 = 33,
+#define GR21	GR21
+  GR22 = 34,
+#define GR22	GR22
+  GR23 = 35,
+#define GR23	GR23
+  GR24 = 36,
+#define GR24	GR24
+  GR25 = 37,
+#define GR25	GR25
+  GR26 = 38,
+#define GR26	GR26
+  GR27 = 39,
+#define GR27	GR27
+  GR28 = 40,
+#define GR28	GR28
+  GR29 = 41,
+#define GR29	GR29
+  GR30 = 42,
+#define GR30	GR30
+  GR31 = 43,
+#define GR31	GR31
+  GR32 = 44,
+#define GR32	GR32
+  GR33 = 45,
+#define GR33	GR33
+  GR34 = 46,
+#define GR34	GR34
+  GR35 = 47,
+#define GR35	GR35
+  GR36 = 48,
+#define GR36	GR36
+  GR37 = 49,
+#define GR37	GR37
+  GR38 = 50,
+#define GR38	GR38
+  GR39 = 51,
+#define GR39	GR39
+  GR40 = 52,
+#define GR40	GR40
+  GR41 = 53,
+#define GR41	GR41
+  GR42 = 54,
+#define GR42	GR42
+  GR43 = 55,
+#define GR43	GR43
+  GR44 = 56,
+#define GR44	GR44
+  GR45 = 57,
+#define GR45	GR45
+  GR46 = 58,
+#define GR46	GR46
+  GR47 = 59,
+#define GR47	GR47
+  GR48 = 60,
+#define GR48	GR48
+  GR49 = 61,
+#define GR49	GR49
+  GR50 = 62,
+#define GR50	GR50
+  GR51 = 63,
+#define GR51	GR51
+  GR52 = 64,
+#define GR52	GR52
+  GR53 = 65,
+#define GR53	GR53
+  GR54 = 66,
+#define GR54	GR54
+  GR55 = 67,
+#define GR55	GR55
+  GR56 = 68,
+#define GR56	GR56
+  GR57 = 69,
+#define GR57	GR57
+  GR58 = 70,
+#define GR58	GR58
+  GR59 = 71,
+#define GR59	GR59
+  GR60 = 72,
+#define GR60	GR60
+  GR61 = 73,
+#define GR61	GR61
+  GR62 = 74,
+#define GR62	GR62
+  GR63 = 75,
+#define GR63	GR63
+};
+#endif
+
+typedef unsigned long freg_t;
+
+/* Number of FPU registers.  */
+#define NFPREG	(64+2+2+8+2+1)
+
+#ifdef __USE_GNU
+/* Number of each register is the `gregset_t' array.  */
+enum
+{
+  FR0 = 0,
+#define FR0	FR0
+  FR1 = 1,
+#define FR1	FR1
+  FR2 = 2,
+#define FR2	FR2
+  FR3 = 3,
+#define FR3	FR3
+  FR4 = 4,
+#define FR4	FR4
+  FR5 = 5,
+#define FR5	FR5
+  FR6 = 6,
+#define FR6	FR6
+  FR7 = 7,
+#define FR7	FR7
+  FR8 = 8,
+#define FR8	FR8
+  FR9 = 9,
+#define FR9	FR9
+  FR10 = 10,
+#define FR10	FR10
+  FR11 = 11,
+#define FR11	FR11
+  FR12 = 12,
+#define FR12	FR12
+  FR13 = 13,
+#define FR13	FR13
+  FR14 = 14,
+#define FR14	FR14
+  FR15 = 15,
+#define FR15	FR15
+  FR16 = 16,
+#define FR16	FR16
+  FR17 = 17,
+#define FR17	FR17
+  FR18 = 18,
+#define FR18	FR18
+  FR19 = 19,
+#define FR19	FR19
+  FR20 = 20,
+#define FR20	FR20
+  FR21 = 21,
+#define FR21	FR21
+  FR22 = 22,
+#define FR22	FR22
+  FR23 = 23,
+#define FR23	FR23
+  FR24 = 24,
+#define FR24	FR24
+  FR25 = 25,
+#define FR25	FR25
+  FR26 = 26,
+#define FR26	FR26
+  FR27 = 27,
+#define FR27	FR27
+  FR28 = 28,
+#define FR28	FR28
+  FR29 = 29,
+#define FR29	FR29
+  FR30 = 30,
+#define FR30	FR30
+  FR31 = 31,
+#define FR31	FR31
+  FR32 = 32,
+#define FR32	FR32
+  FR33 = 33,
+#define FR33	FR33
+  FR34 = 34,
+#define FR34	FR34
+  FR35 = 35,
+#define FR35	FR35
+  FR36 = 36,
+#define FR36	FR36
+  FR37 = 37,
+#define FR37	FR37
+  FR38 = 38,
+#define FR38	FR38
+  FR39 = 39,
+#define FR39	FR39
+  FR40 = 40,
+#define FR40	FR40
+  FR41 = 41,
+#define FR41	FR41
+  FR42 = 42,
+#define FR42	FR42
+  FR43 = 43,
+#define FR43	FR43
+  FR44 = 44,
+#define FR44	FR44
+  FR45 = 45,
+#define FR45	FR45
+  FR46 = 46,
+#define FR46	FR46
+  FR47 = 47,
+#define FR47	FR47
+  FR48 = 48,
+#define FR48	FR48
+  FR49 = 49,
+#define FR49	FR49
+  FR50 = 50,
+#define FR50	FR50
+  FR51 = 51,
+#define FR51	FR51
+  FR52 = 52,
+#define FR52	FR52
+  FR53 = 53,
+#define FR53	FR53
+  FR54 = 54,
+#define FR54	FR54
+  FR55 = 55,
+#define FR55	FR55
+  FR56 = 56,
+#define FR56	FR56
+  FR57 = 57,
+#define FR57	FR57
+  FR58 = 58,
+#define FR58	FR58
+  FR59 = 59,
+#define FR59	FR59
+  FR60 = 60,
+#define FR60	FR60
+  FR61 = 61,
+#define FR61	FR61
+  FR62 = 62,
+#define FR62	FR62
+  FR63 = 63,
+#define FR63	FR63
+  FNER0 = 64,
+#define FNER0	FNER0
+  FNER1 = 65,
+#define FNER1	FNER1
+  MSR0 = 66,
+#define MSR0	MSR0
+  MSR1 = 67,
+#define MSR1	MSR1
+  ACC0 = 68,
+#define ACC0	ACC0
+  ACC1 = 69,
+#define ACC1	ACC1
+  ACC2 = 70,
+#define ACC2	ACC2
+  ACC3 = 71,
+#define ACC3	ACC3
+  ACC4 = 72,
+#define ACC4	ACC4
+  ACC5 = 73,
+#define ACC5	ACC5
+  ACC6 = 74,
+#define ACC6	ACC6
+  ACC7 = 75,
+#define ACC7	ACC7
+  ACCG0123 = 76,
+#define ACCG0123	ACCG0123
+  ACCG4567 = 77,
+#define ACCG4567	ACCG4567
+  FSR0 = 78,
+#define FSR0	FSR0
+};
+#endif
+
+/* Structure to describe FPU registers.  */
+typedef freg_t fpregset_t[NFPREG];
+
+/* Context to describe whole processor state.  */
+typedef struct
+  {
+    gregset_t gregs;
+    fpregset_t fpregs;
+    void *extension;
+    unsigned long sc_oldmask; 	/* old sigmask */
+  } __attribute__((aligned(8))) mcontext_t;
+
+#ifdef __USE_GNU
+struct kernel_user_int_regs
+{
+  /* integer registers
+   * - up to gr[31] mirror pt_regs in the kernel
+   */
+  unsigned long		psr;		/* Processor Status Register */
+  unsigned long		isr;		/* Integer Status Register */
+  unsigned long		ccr;		/* Condition Code Register */
+  unsigned long		cccr;		/* Condition Code for Conditional Insns Register */
+  unsigned long		lr;		/* Link Register */
+  unsigned long		lcr;		/* Loop Count Register */
+  unsigned long		pc;		/* Program Counter Register */
+  unsigned long		__status;	/* exception status */
+  unsigned long		syscallno;	/* syscall number or -1 */
+  unsigned long		orig_gr8;	/* original syscall arg #1 */
+  unsigned long		gner[2];
+
+  union {
+    unsigned long	tbr;
+    unsigned long	gr[64];
+  };
+};
+
+struct kernel_user_fpmedia_regs
+{
+  /* FP/Media registers */
+  unsigned long	fr[64];
+  unsigned long	fner[2];
+  unsigned long	msr[2];
+  unsigned long	acc[8];
+  unsigned char	accg[8];
+  unsigned long	fsr[1];
+};
+
+struct kernel_user_context
+{
+  struct kernel_user_int_regs i;
+  struct kernel_user_fpmedia_regs f;
+
+  /* we provide a context extension so that we can save the regs for CPUs that
+   * implement many more of Fujitsu's lavish register spec
+   */
+  void			*extension;
+
+  /* This is not part of the kernel's struct user_context, but
+     rather of the enclosing struct sigcontext, but we add it
+     here to parallel mcontext_t, just for completeness.  */
+  unsigned long sc_oldmask; 	/* old sigmask */
+} __attribute__((aligned(8)));
+
+/* This union enables alias-safe casts from mcontext_t* to the union
+   type, that can then be dereferenced as_aliases.  */
+union kmcontext_t
+{
+  mcontext_t as_regsets;
+  /* as_aliases is actually missing sc_oldmask, that is present in
+     mcontext_t.  */
+  struct kernel_user_context as_aliases;
+};
+#endif
+
+/* Userlevel context.  */
+typedef struct ucontext
+  {
+    unsigned long int uc_flags;
+    struct ucontext *uc_link;
+    stack_t uc_stack;
+    mcontext_t uc_mcontext;
+    __sigset_t uc_sigmask;
+  } ucontext_t;
+
+#endif /* sys/ucontext.h */