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/*
* Copyright (C) 2012 The Android Open Source Project
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#ifndef _ARCH_X86_SYS_UCONTEXT_H_
#define _ARCH_X86_SYS_UCONTEXT_H_
#include <signal.h>
#include <stdint.h>
__BEGIN_DECLS
/* Technical note:
*
* On x86, there are differences in the way GLibc and the Linux kernel declare
* ucontext_t. Here are the details (they differ from ARM significantly):
*
* - The kernel implements 'uc_mcontext' with a 'struct sigcontext',
* while GLibc defines 'mcontext_t' in a binary-compatible way
* (same size, same binary layout), but with different field naming/access
* conventions.
*
* The biggest difference is that 'struct sigcontext' requires named fields
* like "eax", or "ebp" to access the state of register values, while GLibc
* provides an array (gregs[]) of 32-bit values, that can be accessed
* through indexing, plus some enum/macros like REG_EAX or REG_ESP to get
* to specific register values.
*
* For maximum portability of existing client code, this header follows
* the GLibc convention. Client code, and the C library, should never
* try to include <asm/ucontext.h>
*
* - The floating-point state is not stored in the mcontext_t. For historical
* reasons, the 'fpregs' field of 'mcontext_t' is really a pointer to a
* different block of memory. More specifically:
*
* * When passed to a signal handler, the pointer points to some memory
* on the signal stack, populated by the kernel before calling the
* handler in user space.
*
* * In GLibc's getcontext()/setcontext() implementation, the pointer will
* point to the ucontext_t structure (more specifically the __fpregs_mem
* field after uc_sigmask).
*
* * Note that in both cases, the pointer can be NULL if no floating-point
* operation has been performed on the current thread yet.
*
* - The 'struct _libc_fpstate' structure declared by GLibc corresponds to
* both the FP state managed by getcontext()/setcontext(), and the start
* of the FP state stored by the kernel and passed to a signal handler.
*
* This matches the data saved by the FNSTENV IA-32 instruction.
*
* IMPORTANT: GLibc does not save the MMX/SSE state, i.e. it does not use
* FXSAVE / FXRSTOR instructions in *context() functions.
*
* It is used by client code to retrieve the state of the FPU registers
* (e.g. Google Breakpad does that).
*
* Reference source files:
* $KERNEL/arch/x86/include/asm/sigcontext_32.h
* $KERNEL/arch/x86/include/asm/sigcontext.h
* $KERNEL/arch/x86/include/asm/ucontext.h
*
* $GLIBC/sysdeps/unix/sysv/linux/i386/getcontext.S
* $GLIBC/sysdeps/unix/sysv/linux/i386/setcontext.S
* $GLIBC/sysdeps/unix/sysv/linux/x86/sys/ucontext.h
*/
/* First, the kernel-compatible version, for reference. */
typedef struct __kernel_ucontext {
unsigned long uc_flags;
struct __kernel_ucontext* uc_link;
stack_t uc_stack;
struct sigcontext uc_mcontext;
__kernel_sigset_t uc_sigmask;
} __kernel_ucontext_t;
/* Second, the GLibc-compatible version */
#define NGREG 19
typedef int greg_t;
typedef greg_t gregset_t[NGREG];
enum {
REG_GS = 0, REG_FS, REG_ES, REG_DS,
REG_EDI, REG_ESI, REG_EBP, REG_ESP,
REG_EBX, REG_EDX, REG_ECX, REG_EAX,
REG_TRAPNO, REG_ERR, REG_EIP, REG_CS,
REG_EFL, REG_UESP, REG_SS
};
/* GLibc defines both macros and enums. Probably to let client do
* #ifdef REG_XXXX ... #endif. Do the same here. */
#define REG_GS REG_GS
#define REG_FS REG_FS
#define REG_ES REG_ES
#define REG_DS REG_DS
#define REG_EDI REG_EDI
#define REG_ESI REG_ESI
#define REG_EBP REG_EBP
#define REG_ESP REG_ESP
#define REG_EBX REG_EBX
#define REG_EDX REG_EDX
#define REG_ECX REG_ECX
#define REG_EAX REG_EAX
#define REG_TRAPNO REG_TRAPNO
#define REG_ERR REG_ERR
#define REG_EIP REG_EIP
#define REG_CS REG_CS
#define REG_EFL REG_EFL
#define REG_UESP REG_UESP
#define REG_SS REG_SS
/* 80-bit floating-point register */
struct _libc_fpreg {
unsigned short significand[4];
unsigned short exponent;
};
/* Simple floating-point state, see FNSTENV instruction */
struct _libc_fpstate {
unsigned long cw;
unsigned long sw;
unsigned long tag;
unsigned long ipoff;
unsigned long cssel;
unsigned long dataoff;
unsigned long datasel;
struct _libc_fpreg _st[8];
unsigned long status;
};
typedef struct _libc_fpstate* fpregset_t;
typedef struct {
gregset_t gregs;
fpregset_t fpregs; /* Really a pointer to _libc_fpstate! */
} mcontext_t;
typedef struct ucontext {
uint32_t uc_flags;
struct ucontext* uc_link;
stack_t uc_stack;
mcontext_t uc_mcontext;
/* Only expose the 32 non-realtime signals in Bionic's 32-bit sigset_t
* The _unused field is required padding from the kernel. */
sigset_t uc_sigmask;
char _unused[sizeof(__kernel_sigset_t) - sizeof(sigset_t)];
/* Storage area for *context() functions only - private, don't use. */
struct _libc_fpstate __fpregs_mem;
/* Growth opportunity - in case we want to save MMX/SSE stuff there too */
int _unused2[128 - sizeof(struct _libc_fpstate)/sizeof(int)];
} ucontext_t;
__END_DECLS
#endif /* _ARCH_X86_SYS_UCONTEXT_H_ */
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