s390: Remove compat support

There shouldn't be any 31 bit code around anymore that matters.
Remove the compat layer support required to run 31 bit code.

Reason for removal is code simplification and reduced test effort.

Note that this comes without any deprecation warnings added to config
options, or kernel messages, since most likely those would be ignored
anyway.

If it turns out there is still a reason to keep the compat layer this
can be reverted at any time in the future.

Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

Author: hcahca

arch/s390/Kconfig

@@ -505,22 +505,6 @@ config COMMAND_LINE_SIZE
 	  This allows you to specify the maximum length of the kernel command
 	  line.
 
-config COMPAT
-	def_bool n
-	prompt "Kernel support for 31 bit emulation"
-	select ARCH_WANT_OLD_COMPAT_IPC
-	select COMPAT_OLD_SIGACTION
-	select HAVE_UID16
-	depends on MULTIUSER
-	depends on !CC_IS_CLANG && !LD_IS_LLD
-	help
-	  Select this option if you want to enable your system kernel to
-	  handle system-calls from ELF binaries for 31 bit ESA.  This option
-	  (and some other stuff like libraries and such) is needed for
-	  executing 31 bit applications.
-
-	  If unsure say N.
-
 config SMP
 	def_bool y
 

arch/s390/Makefile

@@ -149,11 +149,8 @@ ifeq ($(KBUILD_EXTMOD),)
 prepare: vdso_prepare
 vdso_prepare: prepare0
 	$(Q)$(MAKE) $(build)=arch/s390/kernel/vdso64 include/generated/vdso64-offsets.h
-	$(if $(CONFIG_COMPAT),$(Q)$(MAKE) \
-		$(build)=arch/s390/kernel/vdso32 include/generated/vdso32-offsets.h)
 
 vdso-install-y			+= arch/s390/kernel/vdso64/vdso64.so.dbg
-vdso-install-$(CONFIG_COMPAT)	+= arch/s390/kernel/vdso32/vdso32.so.dbg
 
 endif
 

arch/s390/boot/ipl_data.c

@@ -1,6 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
 
-#include <linux/compat.h>
 #include <linux/ptrace.h>
 #include <asm/cio.h>
 #include <asm/asm-offsets.h>

arch/s390/configs/compat.config

@@ -7,7 +7,6 @@
  *    Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com>
  */
 
-#include <linux/compat.h>
 #include <linux/errno.h>
 #include <linux/gfp.h>
 #include <linux/string.h>
@@ -116,10 +115,7 @@ static long hypfs_sprp_ioctl(struct file *file, unsigned int cmd,
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EACCES;
-	if (is_compat_task())
-		argp = compat_ptr(arg);
-	else
-		argp = (void __user *) arg;
+	argp = (void __user *)arg;
 	switch (cmd) {
 	case HYPFS_DIAG304:
 		return __hypfs_sprp_ioctl(argp);

arch/s390/hypfs/hypfs_sprp.c

@@ -162,18 +162,13 @@ enum {
  * ELF register definitions..
  */
 
-#include <linux/compat.h>
-
 #include <asm/ptrace.h>
 #include <asm/syscall.h>
 #include <asm/user.h>
 
 typedef s390_fp_regs elf_fpregset_t;
 typedef s390_regs elf_gregset_t;
 
-typedef s390_fp_regs compat_elf_fpregset_t;
-typedef s390_compat_regs compat_elf_gregset_t;
-
 #include <linux/sched/mm.h>	/* for task_struct */
 #include <asm/mmu_context.h>
 
@@ -183,10 +178,6 @@ typedef s390_compat_regs compat_elf_gregset_t;
 #define elf_check_arch(x) \
 	(((x)->e_machine == EM_S390 || (x)->e_machine == EM_S390_OLD) \
          && (x)->e_ident[EI_CLASS] == ELF_CLASS) 
-#define compat_elf_check_arch(x) \
-	(((x)->e_machine == EM_S390 || (x)->e_machine == EM_S390_OLD) \
-	 && (x)->e_ident[EI_CLASS] == ELF_CLASS)
-#define compat_start_thread	start_thread31
 
 /* For SVR4/S390 the function pointer to be registered with `atexit` is
    passed in R14. */
@@ -203,9 +194,7 @@ typedef s390_compat_regs compat_elf_gregset_t;
    the loader.  We need to make sure that it is out of the way of the program
    that it will "exec", and that there is sufficient room for the brk. 64-bit
    tasks are aligned to 4GB. */
-#define ELF_ET_DYN_BASE (is_compat_task() ? \
-				(STACK_TOP / 3 * 2) : \
-				(STACK_TOP / 3 * 2) & ~((1UL << 32) - 1))
+#define ELF_ET_DYN_BASE ((STACK_TOP / 3 * 2) & ~((1UL << 32) - 1))
 
 /* This yields a mask that user programs can use to figure out what
    instruction set this CPU supports. */
@@ -224,43 +213,22 @@ extern unsigned long elf_hwcap;
 extern char elf_platform[];
 #define ELF_PLATFORM (elf_platform)
 
-#ifndef CONFIG_COMPAT
 #define SET_PERSONALITY(ex) \
 do {								\
 	set_personality(PER_LINUX |				\
 		(current->personality & (~PER_MASK)));		\
 	current->thread.sys_call_table = sys_call_table;	\
 } while (0)
-#else /* CONFIG_COMPAT */
-#define SET_PERSONALITY(ex)					\
-do {								\
-	if (personality(current->personality) != PER_LINUX32)	\
-		set_personality(PER_LINUX |			\
-			(current->personality & ~PER_MASK));	\
-	if ((ex).e_ident[EI_CLASS] == ELFCLASS32) {		\
-		set_thread_flag(TIF_31BIT);			\
-		current->thread.sys_call_table =		\
-			sys_call_table_emu;			\
-	} else {						\
-		clear_thread_flag(TIF_31BIT);			\
-		current->thread.sys_call_table =		\
-			sys_call_table;				\
-	}							\
-} while (0)
-#endif /* CONFIG_COMPAT */
 
 /*
  * Cache aliasing on the latest machines calls for a mapping granularity
- * of 512KB for the anonymous mapping base. For 64-bit processes use a
- * 512KB alignment and a randomization of up to 1GB. For 31-bit processes
- * the virtual address space is limited, use no alignment and limit the
- * randomization to 8MB.
- * For the additional randomization of the program break use 32MB for
- * 64-bit and 8MB for 31-bit.
+ * of 512KB for the anonymous mapping base. Use a 512KB alignment and a
+ * randomization of up to 1GB.
+ * For the additional randomization of the program break use 32MB.
  */
-#define BRK_RND_MASK	(is_compat_task() ? 0x7ffUL : 0x1fffUL)
-#define MMAP_RND_MASK	(is_compat_task() ? 0x7ffUL : 0x3ff80UL)
-#define MMAP_ALIGN_MASK	(is_compat_task() ? 0 : 0x7fUL)
+#define BRK_RND_MASK	(0x1fffUL)
+#define MMAP_RND_MASK	(0x3ff80UL)
+#define MMAP_ALIGN_MASK	(0x7fUL)
 #define STACK_RND_MASK	MMAP_RND_MASK
 
 /* update AT_VECTOR_SIZE_ARCH if the number of NEW_AUX_ENT entries changes */

arch/s390/include/asm/compat.h

@@ -105,28 +105,11 @@ static inline void arch_ftrace_set_direct_caller(struct ftrace_regs *fregs, unsi
 }
 #endif /* CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS */
 
-/*
- * Even though the system call numbers are identical for s390/s390x a
- * different system call table is used for compat tasks. This may lead
- * to e.g. incorrect or missing trace event sysfs files.
- * Therefore simply do not trace compat system calls at all.
- * See kernel/trace/trace_syscalls.c.
- */
-#define ARCH_TRACE_IGNORE_COMPAT_SYSCALLS
-static inline bool arch_trace_is_compat_syscall(struct pt_regs *regs)
-{
-	return is_compat_task();
-}
-
 #define ARCH_HAS_SYSCALL_MATCH_SYM_NAME
 static inline bool arch_syscall_match_sym_name(const char *sym,
 					       const char *name)
 {
-	/*
-	 * Skip __s390_ and __s390x_ prefix - due to compat wrappers
-	 * and aliasing some symbols of 64 bit system call functions
-	 * may get the __s390_ prefix instead of the __s390x_ prefix.
-	 */
+	/* Skip the __s390x_ prefix. */
 	return !strcmp(sym + 7, name) || !strcmp(sym + 8, name);
 }
 

arch/s390/include/asm/elf.h

@@ -119,18 +119,12 @@ extern void execve_tail(void);
 unsigned long vdso_text_size(void);
 unsigned long vdso_size(void);
 
-/*
- * User space process size: 2GB for 31 bit, 4TB or 8PT for 64 bit.
- */
-
-#define TASK_SIZE		(test_thread_flag(TIF_31BIT) ? \
-					_REGION3_SIZE : TASK_SIZE_MAX)
-#define TASK_UNMAPPED_BASE	(test_thread_flag(TIF_31BIT) ? \
-					(_REGION3_SIZE >> 1) : (_REGION2_SIZE >> 1))
+#define TASK_SIZE		(TASK_SIZE_MAX)
+#define TASK_UNMAPPED_BASE	(_REGION2_SIZE >> 1)
 #define TASK_SIZE_MAX		(-PAGE_SIZE)
 
 #define VDSO_BASE		(STACK_TOP + PAGE_SIZE)
-#define VDSO_LIMIT		(test_thread_flag(TIF_31BIT) ? _REGION3_SIZE : _REGION2_SIZE)
+#define VDSO_LIMIT		(_REGION2_SIZE)
 #define STACK_TOP		(VDSO_LIMIT - vdso_size() - PAGE_SIZE)
 #define STACK_TOP_MAX		(_REGION2_SIZE - vdso_size() - PAGE_SIZE)
 

arch/s390/include/asm/ftrace.h

@@ -19,10 +19,5 @@
 #define SECCOMP_ARCH_NATIVE		AUDIT_ARCH_S390X
 #define SECCOMP_ARCH_NATIVE_NR		NR_syscalls
 #define SECCOMP_ARCH_NATIVE_NAME	"s390x"
-#ifdef CONFIG_COMPAT
-# define SECCOMP_ARCH_COMPAT		AUDIT_ARCH_S390
-# define SECCOMP_ARCH_COMPAT_NR		NR_syscalls
-# define SECCOMP_ARCH_COMPAT_NAME	"s390"
-#endif
 
 #endif	/* _ASM_S390_SECCOMP_H */