arm64: Exception handling

The patch contains the exception entry code (kernel/entry.S), pt_regs
structure and related accessors, undefined instruction trapping and
stack tracing.

AArch64 Linux kernel (including kernel threads) runs in EL1 mode using
the SP1 stack. The vectors don't have a fixed address, only alignment
(2^11) requirements.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Tony Lindgren <tony@atomide.com>
Acked-by: Nicolas Pitre <nico@linaro.org>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>

arch/arm64/include/asm/ptrace.h

@@ -0,0 +1,212 @@
+/*
+ * Based on arch/arm/include/asm/ptrace.h
+ *
+ * Copyright (C) 1996-2003 Russell King
+ * 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_PTRACE_H
+#define __ASM_PTRACE_H
+
+#include <linux/types.h>
+
+#include <asm/hwcap.h>
+
+#define PTRACE_GETREGS		12
+#define PTRACE_SETREGS		13
+#define PTRACE_GETFPSIMDREGS	14
+#define PTRACE_SETFPSIMDREGS	15
+/* PTRACE_ATTACH is 16 */
+/* PTRACE_DETACH is 17 */
+#define PTRACE_GET_THREAD_AREA	22
+#define PTRACE_SET_SYSCALL	23
+#define PTRACE_GETHBPREGS	29
+#define PTRACE_SETHBPREGS	30
+
+/* AArch32-specific ptrace requests */
+#define COMPAT_PTRACE_GETVFPREGS	27
+#define COMPAT_PTRACE_SETVFPREGS	28
+
+/*
+ * PSR bits
+ */
+#define PSR_MODE_EL0t	0x00000000
+#define PSR_MODE_EL1t	0x00000004
+#define PSR_MODE_EL1h	0x00000005
+#define PSR_MODE_EL2t	0x00000008
+#define PSR_MODE_EL2h	0x00000009
+#define PSR_MODE_EL3t	0x0000000c
+#define PSR_MODE_EL3h	0x0000000d
+#define PSR_MODE_MASK	0x0000000f
+
+/* AArch32 CPSR bits */
+#define PSR_MODE32_BIT		0x00000010
+#define COMPAT_PSR_MODE_USR	0x00000010
+#define COMPAT_PSR_T_BIT	0x00000020
+#define COMPAT_PSR_IT_MASK	0x0600fc00	/* If-Then execution state mask */
+
+/* AArch64 SPSR bits */
+#define PSR_F_BIT	0x00000040
+#define PSR_I_BIT	0x00000080
+#define PSR_A_BIT	0x00000100
+#define PSR_D_BIT	0x00000200
+#define PSR_Q_BIT	0x08000000
+#define PSR_V_BIT	0x10000000
+#define PSR_C_BIT	0x20000000
+#define PSR_Z_BIT	0x40000000
+#define PSR_N_BIT	0x80000000
+
+/*
+ * Groups of PSR bits
+ */
+#define PSR_f		0xff000000	/* Flags		*/
+#define PSR_s		0x00ff0000	/* Status		*/
+#define PSR_x		0x0000ff00	/* Extension		*/
+#define PSR_c		0x000000ff	/* Control		*/
+
+/*
+ * These are 'magic' values for PTRACE_PEEKUSR that return info about where a
+ * process is located in memory.
+ */
+#define PT_TEXT_ADDR		0x10000
+#define PT_DATA_ADDR		0x10004
+#define PT_TEXT_END_ADDR	0x10008
+
+#ifndef __ASSEMBLY__
+
+/*
+ * User structures for general purpose, floating point and debug registers.
+ */
+struct user_pt_regs {
+	__u64		regs[31];
+	__u64		sp;
+	__u64		pc;
+	__u64		pstate;
+};
+
+struct user_fpsimd_state {
+	__uint128_t	vregs[32];
+	__u32		fpsr;
+	__u32		fpcr;
+};
+
+struct user_hwdebug_state {
+	__u32		dbg_info;
+	struct {
+		__u64	addr;
+		__u32	ctrl;
+	}		dbg_regs[16];
+};
+
+#ifdef __KERNEL__
+
+/* sizeof(struct user) for AArch32 */
+#define COMPAT_USER_SZ	296
+/* AArch32 uses x13 as the stack pointer... */
+#define compat_sp	regs[13]
+/* ... and x14 as the link register. */
+#define compat_lr	regs[14]
+
+/*
+ * This struct defines the way the registers are stored on the stack during an
+ * exception. Note that sizeof(struct pt_regs) has to be a multiple of 16 (for
+ * stack alignment). struct user_pt_regs must form a prefix of struct pt_regs.
+ */
+struct pt_regs {
+	union {
+		struct user_pt_regs user_regs;
+		struct {
+			u64 regs[31];
+			u64 sp;
+			u64 pc;
+			u64 pstate;
+		};
+	};
+	u64 orig_x0;
+	u64 syscallno;
+};
+
+#define arch_has_single_step()	(1)
+
+#ifdef CONFIG_COMPAT
+#define compat_thumb_mode(regs) \
+	(((regs)->pstate & COMPAT_PSR_T_BIT))
+#else
+#define compat_thumb_mode(regs) (0)
+#endif
+
+#define user_mode(regs)	\
+	(((regs)->pstate & PSR_MODE_MASK) == PSR_MODE_EL0t)
+
+#define compat_user_mode(regs)	\
+	(((regs)->pstate & (PSR_MODE32_BIT | PSR_MODE_MASK)) == \
+	 (PSR_MODE32_BIT | PSR_MODE_EL0t))
+
+#define processor_mode(regs) \
+	((regs)->pstate & PSR_MODE_MASK)
+
+#define interrupts_enabled(regs) \
+	(!((regs)->pstate & PSR_I_BIT))
+
+#define fast_interrupts_enabled(regs) \
+	(!((regs)->pstate & PSR_F_BIT))
+
+#define user_stack_pointer(regs) \
+	((regs)->sp)
+
+/*
+ * Are the current registers suitable for user mode? (used to maintain
+ * security in signal handlers)
+ */
+static inline int valid_user_regs(struct user_pt_regs *regs)
+{
+	if (user_mode(regs) && (regs->pstate & PSR_I_BIT) == 0) {
+		regs->pstate &= ~(PSR_F_BIT | PSR_A_BIT);
+
+		/* The T bit is reserved for AArch64 */
+		if (!(regs->pstate & PSR_MODE32_BIT))
+			regs->pstate &= ~COMPAT_PSR_T_BIT;
+
+		return 1;
+	}
+
+	/*
+	 * Force PSR to something logical...
+	 */
+	regs->pstate &= PSR_f | PSR_s | (PSR_x & ~PSR_A_BIT) | \
+			COMPAT_PSR_T_BIT | PSR_MODE32_BIT;
+
+	if (!(regs->pstate & PSR_MODE32_BIT)) {
+		regs->pstate &= ~COMPAT_PSR_T_BIT;
+		regs->pstate |= PSR_MODE_EL0t;
+	}
+
+	return 0;
+}
+
+#define instruction_pointer(regs)	(regs)->pc
+
+#ifdef CONFIG_SMP
+extern unsigned long profile_pc(struct pt_regs *regs);
+#else
+#define profile_pc(regs) instruction_pointer(regs)
+#endif
+
+extern int aarch32_break_trap(struct pt_regs *regs);
+
+#endif /* __KERNEL__ */
+
+#endif /* __ASSEMBLY__ */
+
+#endif

arch/arm64/include/asm/stacktrace.h

@@ -0,0 +1,29 @@
+/*
+ * 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_STACKTRACE_H
+#define __ASM_STACKTRACE_H
+
+struct stackframe {
+	unsigned long fp;
+	unsigned long sp;
+	unsigned long pc;
+};
+
+extern int unwind_frame(struct stackframe *frame);
+extern void walk_stackframe(struct stackframe *frame,
+			    int (*fn)(struct stackframe *, void *), void *data);
+
+#endif	/* __ASM_STACKTRACE_H */

arch/arm64/include/asm/traps.h

@@ -0,0 +1,30 @@
+/*
+ * Based on arch/arm/include/asm/traps.h
+ *
+ * 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_TRAP_H
+#define __ASM_TRAP_H
+
+static inline int in_exception_text(unsigned long ptr)
+{
+	extern char __exception_text_start[];
+	extern char __exception_text_end[];
+
+	return ptr >= (unsigned long)&__exception_text_start &&
+	       ptr < (unsigned long)&__exception_text_end;
+}
+
+#endif