libc: Provide ucontext_t/mcontext_t/<sys/ucontext.h>
This patch updates the C library headers to provide ucontext_t
definitions for three architectures.
+ Fix <signal.h> to always define 'struct sigcontext'.
The new declarations are announced with new macros defined in
<sys/cdefs.h> in order to make it easier to adapt client code
that already defines its own, incompatible, versions of the
structures seen here.
http://code.google.com/p/android/issues/detail?id=34784
Change-Id: Ie78c48690a4ce61c50593f6c39639be7fead3596
diff --git a/libc/arch-x86/include/machine/signal.h b/libc/arch-x86/include/machine/signal.h
new file mode 100644
index 0000000..ba3fe37
--- /dev/null
+++ b/libc/arch-x86/include/machine/signal.h
@@ -0,0 +1,67 @@
+/*
+ * 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_MACHINE_SIGNAL_H_
+#define _ARCH_X86_MACHINE_SIGNAL_H_
+
+#include <stddef.h>
+#include <sys/types.h>
+#include <sys/cdefs.h>
+
+__BEGIN_DECLS
+
+#include <asm/signal.h>
+#include <asm/sigcontext.h>
+
+#ifdef _ASM_GENERIC_SIGINFO_H
+#error "You cannot include <asm/siginfo.h> before <signal.h>!"
+#endif
+#define __ARCH_SI_UID_T __kernel_uid32_t
+#include <asm/siginfo.h>
+#undef __ARCH_SI_UID_T
+
+#include <stdint.h>
+
+/* See comment in arch-arm/include/machine/signal.h.
+ * The x86 kernel also uses 64-bit signal masks while defining sigset-t
+ * as a 32-bit type.
+ */
+typedef unsigned long __kernel_sigset_t[2];
+
+/* _NSIG is used by the SIGRTMAX definition under <asm/signal.h>, however
+ * its definition is part of a #if __KERNEL__ .. #endif block in the original
+ * kernel headers and is thus not part of our cleaned-up versions.
+ *
+ * Looking at the current kernel sources, it is defined as 64 for x86.
+ */
+#ifndef _NSIG
+# define _NSIG 64
+#endif
+
+__END_DECLS
+
+#endif /* _ARCH_X86_MACHINE_SIGNAL_H_ */
diff --git a/libc/arch-x86/include/machine/ucontext.h b/libc/arch-x86/include/machine/ucontext.h
new file mode 100644
index 0000000..da226c9
--- /dev/null
+++ b/libc/arch-x86/include/machine/ucontext.h
@@ -0,0 +1,184 @@
+/*
+ * 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_ */