arm64: ilp32: introduce ilp32-specific sigframe and ucontext

maillist inclusion
category: feature
bugzilla: 46790
CVE: NA

Reference: https://github.com/norov/linux/commits/ilp32-5.2

--------------------------------

ILP32 uses AARCH32 compat structures and syscall handlers for signals. But
ILP32 rt_sigframe and ucontext structures differ from both LP64 and AARCH32.
>From software point of view ILP32 is typical 32-bit compat ABI, and from
hardware point of view, it's just like LP64.

struct rt_sigframe defined in this patch in
arch/arm64/kernel/signal_ilp32.c redefines one in
arch/arm64/kernel/signal.c. And functions located in
arch/arm64/include/signal_common.h pick up new structure to generate the
code suitable for ILP32.
Signed-off-by: NYury Norov <ynorov@caviumnetworks.com>
Signed-off-by: NYury Norov <ynorov@marvell.com>
Signed-off-by: NXiongfeng Wang <wangxiongfeng2@huawei.com>
Acked-by: NXie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: NChen Jun <chenjun102@huawei.com>

arch/arm64/include/asm/signal_ilp32.h

+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef __ASM_SIGNAL_ILP32_H
+#define __ASM_SIGNAL_ILP32_H
+
+#ifdef CONFIG_ARM64_ILP32
+
+#include <linux/compat.h>
+
+int ilp32_setup_rt_frame(int usig, struct ksignal *ksig, sigset_t *set,
+			  struct pt_regs *regs);
+
+#else
+
+static inline int ilp32_setup_rt_frame(int usig, struct ksignal *ksig,
+					sigset_t *set, struct pt_regs *regs)
+{
+	return -ENOSYS;
+}
+
+#endif /* CONFIG_ARM64_ILP32 */
+
+#endif /* __ASM_SIGNAL_ILP32_H */

arch/arm64/kernel/Makefile

@@ -29,7 +29,8 @@ obj-$(CONFIG_AARCH32_EL0)			+= binfmt_elf32.o sys32.o signal32.o			\
 					   sys_compat.o
 obj-$(CONFIG_AARCH32_EL0)			+= sigreturn32.o
 obj-$(CONFIG_KUSER_HELPERS)		+= kuser32.o
-obj-$(CONFIG_ARM64_ILP32)		+= binfmt_ilp32.o sys_ilp32.o
+obj-$(CONFIG_ARM64_ILP32)		+= binfmt_ilp32.o sys_ilp32.o 		\
+					   signal_ilp32.o
 obj-$(CONFIG_COMPAT)		+= sys32_common.o signal32_common.o
 obj-$(CONFIG_FUNCTION_TRACER)		+= ftrace.o entry-ftrace.o
 obj-$(CONFIG_MODULES)			+= module.o

arch/arm64/kernel/signal.c

@@ -32,6 +32,7 @@
 #include <asm/signal32.h>
 #include <asm/traps.h>
 #include <asm/vdso.h>
+#include <asm/signal_ilp32.h>
 
 #define get_sigset(s, m) __copy_from_user(s, m, sizeof(*s))
 #define put_sigset(s, m) __copy_to_user(m, s, sizeof(*s))
@@ -591,6 +592,8 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
 			ret = a32_setup_rt_frame(usig, ksig, oldset, regs);
 		else
 			ret = a32_setup_frame(usig, ksig, oldset, regs);
+	} else if (is_ilp32_compat_task()) {
+		ret = ilp32_setup_rt_frame(usig, ksig, oldset, regs);
 	} else {
 		ret = setup_rt_frame(usig, ksig, oldset, regs);
 	}

arch/arm64/kernel/signal_ilp32.c

+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Copyright (C) 1995-2009 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ * Copyright (C) 2018 Cavium Networks.
+ * Yury Norov <ynorov@caviumnetworks.com>
+ */
+
+#include <linux/compat.h>
+#include <linux/signal.h>
+#include <linux/syscalls.h>
+
+#include <asm/fpsimd.h>
+#include <asm/unistd.h>
+#include <asm/ucontext.h>
+#include <asm/vdso.h>
+
+#include <asm/signal_ilp32.h>
+#include <asm/signal32_common.h>
+
+#define get_sigset(s, m) get_sigset_t(s, m)
+#define put_sigset(s, m) put_sigset_t(m, s)
+
+#define restore_altstack(stack) compat_restore_altstack(stack)
+#define __save_altstack(stack, sp) __compat_save_altstack(stack, sp)
+#define copy_siginfo_to_user(frame_info, ksig_info) \
+		copy_siginfo_to_user32(frame_info, ksig_info)
+
+#define setup_return(regs, ka, user_layout, usig)			\
+{									\
+	__setup_return(regs, ka, user_layout, usig);			\
+	regs->regs[30] =						\
+		(unsigned long)VDSO_SYMBOL(current->mm->context.vdso,	\
+						    sigtramp_ilp32);	\
+}
+
+struct ilp32_ucontext {
+	u32		uc_flags;
+	u32		uc_link;
+	compat_stack_t	uc_stack;
+	compat_sigset_t	uc_sigmask;
+	/* glibc uses a 1024-bit sigset_t */
+	__u8		__unused[1024 / 8 - sizeof(compat_sigset_t)];
+	/* last for future expansion */
+	struct sigcontext uc_mcontext;
+};
+
+struct rt_sigframe {
+	struct compat_siginfo info;
+	struct ilp32_ucontext uc;
+};
+
+#include <asm/signal_common.h>
+
+COMPAT_SYSCALL_DEFINE0(ilp32_rt_sigreturn)
+{
+	struct pt_regs *regs = current_pt_regs();
+
+	return __sys_rt_sigreturn(regs);
+}
+
+int ilp32_setup_rt_frame(int usig, struct ksignal *ksig,
+			  sigset_t *set, struct pt_regs *regs)
+{
+	return __setup_rt_frame(usig, ksig, set, regs);
+}

arch/arm64/kernel/sys_ilp32.c

@@ -55,6 +55,12 @@
 #define __arm64_compat_sys_msgctl		__arm64_compat_sys_old_msgctl
 #define __arm64_compat_sys_shmctl		__arm64_compat_sys_old_shmctl
 
+/*
+ * Using custom wrapper for rt_sigreturn() to handle custom
+ * struct rt_sigframe.
+ */
+#define __arm64_compat_sys_rt_sigreturn		__arm64_compat_sys_ilp32_rt_sigreturn
+
 /*
  * Wrappers to pass the pt_regs argument.
  */