signal: Remove the need for __ARCH_SI_PREABLE_SIZE and SI_PAD_SIZE

Rework the defintion of struct siginfo so that the array padding
struct siginfo to SI_MAX_SIZE can be placed in a union along side of
the rest of the struct siginfo members.  The result is that we no
longer need the __ARCH_SI_PREAMBLE_SIZE or SI_PAD_SIZE definitions.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

arch/alpha/include/uapi/asm/siginfo.h

@@ -2,7 +2,6 @@
 #ifndef _ALPHA_SIGINFO_H
 #define _ALPHA_SIGINFO_H
 
-#define __ARCH_SI_PREAMBLE_SIZE		(4 * sizeof(int))
 #define __ARCH_SI_TRAPNO
 
 #include <asm-generic/siginfo.h>

arch/arm64/include/uapi/asm/Kbuild

@@ -19,3 +19,4 @@ generic-y += swab.h
 generic-y += termbits.h
 generic-y += termios.h
 generic-y += types.h
+generic-y += siginfo.h

arch/arm64/include/uapi/asm/siginfo.h

-/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
-/*
- * Copyright (C) 2012 ARM Ltd.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * This program 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 General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-#ifndef __ASM_SIGINFO_H
-#define __ASM_SIGINFO_H
-
-#define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))
-
-#include <asm-generic/siginfo.h>
-
-#endif

arch/ia64/include/uapi/asm/siginfo.h

@@ -9,8 +9,6 @@
 #define _UAPI_ASM_IA64_SIGINFO_H
 
 
-#define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))
-
 #include <asm-generic/siginfo.h>
 
 #define si_imm		_sifields._sigfault._imm	/* as per UNIX SysV ABI spec */

arch/mips/include/uapi/asm/siginfo.h

@@ -14,17 +14,6 @@
 #define __ARCH_SIGEV_PREAMBLE_SIZE (sizeof(long) + 2*sizeof(int))
 #undef __ARCH_SI_TRAPNO /* exception code needs to fill this ...  */
 
-/*
- * Careful to keep union _sifields from shifting ...
- */
-#if _MIPS_SZLONG == 32
-#define __ARCH_SI_PREAMBLE_SIZE (3 * sizeof(int))
-#elif _MIPS_SZLONG == 64
-#define __ARCH_SI_PREAMBLE_SIZE (4 * sizeof(int))
-#else
-#error _MIPS_SZLONG neither 32 nor 64
-#endif
-
 #define __ARCH_HAS_SWAPPED_SIGINFO
 
 #include <asm-generic/siginfo.h>

arch/parisc/include/uapi/asm/Kbuild

@@ -7,3 +7,4 @@ generic-y += kvm_para.h
 generic-y += param.h
 generic-y += poll.h
 generic-y += resource.h
+generic-y += siginfo.h

arch/parisc/include/uapi/asm/siginfo.h

-/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
-#ifndef _PARISC_SIGINFO_H
-#define _PARISC_SIGINFO_H
-
-#if defined(__LP64__)
-#define __ARCH_SI_PREAMBLE_SIZE   (4 * sizeof(int))
-#endif
-
-#include <asm-generic/siginfo.h>
-
-#endif

arch/powerpc/include/uapi/asm/Kbuild

@@ -7,3 +7,4 @@ generic-y += poll.h
 generic-y += resource.h
 generic-y += sockios.h
 generic-y += statfs.h
+generic-y += siginfo.h

arch/powerpc/include/uapi/asm/siginfo.h

-/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
-#ifndef _ASM_POWERPC_SIGINFO_H
-#define _ASM_POWERPC_SIGINFO_H
-
-/*
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version
- * 2 of the License, or (at your option) any later version.
- */
-
-#ifdef __powerpc64__
-#    define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))
-#endif
-
-#include <asm-generic/siginfo.h>
-
-#endif	/* _ASM_POWERPC_SIGINFO_H */

arch/riscv/include/uapi/asm/Kbuild

@@ -26,3 +26,4 @@ generic-y += swab.h
 generic-y += termbits.h
 generic-y += termios.h
 generic-y += types.h
+generic-y += siginfo.h

arch/riscv/include/uapi/asm/siginfo.h

-/*
- * Copyright (C) 2012 ARM Ltd.
- * Copyright (C) 2016 SiFive, Inc.
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License version 2 as
- * published by the Free Software Foundation.
- *
- * This program 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 General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program.  If not, see <http://www.gnu.org/licenses/>.
- */
-#ifndef __ASM_SIGINFO_H
-#define __ASM_SIGINFO_H
-
-#define __ARCH_SI_PREAMBLE_SIZE	(__SIZEOF_POINTER__ == 4 ? 12 : 16)
-
-#include <asm-generic/siginfo.h>
-
-#endif

arch/s390/include/uapi/asm/Kbuild

@@ -18,3 +18,4 @@ generic-y += shmbuf.h
 generic-y += sockios.h
 generic-y += swab.h
 generic-y += termbits.h
+generic-y += siginfo.h
\ No newline at end of file

arch/s390/include/uapi/asm/siginfo.h

-/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
-/*
- *  S390 version
- *
- *  Derived from "include/asm-i386/siginfo.h"
- */
-
-#ifndef _S390_SIGINFO_H
-#define _S390_SIGINFO_H
-
-#ifdef __s390x__
-#define __ARCH_SI_PREAMBLE_SIZE (4 * sizeof(int))
-#endif
-
-#include <asm-generic/siginfo.h>
-
-#endif

arch/sparc/include/uapi/asm/siginfo.h

@@ -4,7 +4,6 @@
 
 #if defined(__sparc__) && defined(__arch64__)
 
-#define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))
 #define __ARCH_SI_BAND_T int
 
 #endif /* defined(__sparc__) && defined(__arch64__) */

arch/x86/include/uapi/asm/siginfo.h

@@ -7,8 +7,6 @@
 typedef long long __kernel_si_clock_t __attribute__((aligned(4)));
 #  define __ARCH_SI_CLOCK_T		__kernel_si_clock_t
 #  define __ARCH_SI_ATTRIBUTES		__attribute__((aligned(8)))
-# else /* x86-64 */
-#  define __ARCH_SI_PREAMBLE_SIZE	(4 * sizeof(int))
 # endif
 #endif
 

include/uapi/asm-generic/siginfo.h

@@ -10,18 +10,7 @@ typedef union sigval {
 	void __user *sival_ptr;
 } sigval_t;
 
-/*
- * This is the size (including padding) of the part of the
- * struct siginfo that is before the union.
- */
-#ifndef __ARCH_SI_PREAMBLE_SIZE
-#define __ARCH_SI_PREAMBLE_SIZE	(3 * sizeof(int))
-#endif
-
 #define SI_MAX_SIZE	128
-#ifndef SI_PAD_SIZE
-#define SI_PAD_SIZE	((SI_MAX_SIZE - __ARCH_SI_PREAMBLE_SIZE) / sizeof(int))
-#endif
 
 /*
  * The default "si_band" type is "long", as specified by POSIX.
@@ -40,19 +29,7 @@ typedef union sigval {
 #define __ARCH_SI_ATTRIBUTES
 #endif
 
-typedef struct siginfo {
-	int si_signo;
-#ifndef __ARCH_HAS_SWAPPED_SIGINFO
-	int si_errno;
-	int si_code;
-#else
-	int si_code;
-	int si_errno;
-#endif
-
-	union {
-		int _pad[SI_PAD_SIZE];
-
+union __sifields {
 	/* kill() */
 	struct {
 		__kernel_pid_t _pid;	/* sender's pid */
@@ -129,7 +106,31 @@ typedef struct siginfo {
 		int _syscall;	/* triggering system call number */
 		unsigned int _arch;	/* AUDIT_ARCH_* of syscall */
 	} _sigsys;
-	} _sifields;
+};
+
+#ifndef __ARCH_HAS_SWAPPED_SIGINFO
+#define __SIGINFO 			\
+struct {				\
+	int si_signo;			\
+	int si_errno;			\
+	int si_code;			\
+	union __sifields _sifields;	\
+}
+#else
+#define __SIGINFO 			\
+struct {				\
+	int si_signo;			\
+	int si_code;			\
+	int si_errno;			\
+	union __sifields _sifields;	\
+}
+#endif /* __ARCH_HAS_SWAPPED_SIGINFO */
+
+typedef struct siginfo {
+	union {
+		__SIGINFO;
+		int _si_pad[SI_MAX_SIZE/sizeof(int)];
+	};
 } __ARCH_SI_ATTRIBUTES siginfo_t;
 
 /*

kernel/signal.c

@@ -3963,9 +3963,6 @@ __weak const char *arch_vma_name(struct vm_area_struct *vma)
 
 void __init signals_init(void)
 {
-	/* If this check fails, the __ARCH_SI_PREAMBLE_SIZE value is wrong! */
-	BUILD_BUG_ON(__ARCH_SI_PREAMBLE_SIZE
-		!= offsetof(struct siginfo, _sifields._pad));
 	BUILD_BUG_ON(sizeof(struct siginfo) != SI_MAX_SIZE);
 
 	sigqueue_cachep = KMEM_CACHE(sigqueue, SLAB_PANIC);