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Message-Id: <20170628185538.1804-4-palmer@dabbelt.com>
Date: Wed, 28 Jun 2017 11:55:32 -0700
From: Palmer Dabbelt <palmer@...belt.com>
To: albert@...ive.com
Cc: Palmer Dabbelt <palmer@...belt.com>
Subject: [PATCH 3/9] RISC-V: Generic library routines and assembly
This patch contains code that is more specific to the RISC-V ISA than it
is to Linux. It contains string and math operations, C wrappers for
various assembly instructions, stack walking code, and uaccess.
Signed-off-by: Palmer Dabbelt <palmer@...belt.com>
---
arch/riscv/include/asm/asm.h | 76 ++++++
arch/riscv/include/asm/csr.h | 125 +++++++++
arch/riscv/include/asm/linkage.h | 20 ++
arch/riscv/include/asm/string.h | 30 +++
arch/riscv/include/asm/uaccess.h | 440 ++++++++++++++++++++++++++++++++
arch/riscv/include/asm/word-at-a-time.h | 55 ++++
arch/riscv/kernel/stacktrace.c | 177 +++++++++++++
arch/riscv/lib/memcpy.S | 98 +++++++
arch/riscv/lib/memset.S | 118 +++++++++
arch/riscv/lib/uaccess.S | 125 +++++++++
arch/riscv/lib/udivdi3.S | 38 +++
11 files changed, 1302 insertions(+)
create mode 100644 arch/riscv/include/asm/asm.h
create mode 100644 arch/riscv/include/asm/csr.h
create mode 100644 arch/riscv/include/asm/linkage.h
create mode 100644 arch/riscv/include/asm/string.h
create mode 100644 arch/riscv/include/asm/uaccess.h
create mode 100644 arch/riscv/include/asm/word-at-a-time.h
create mode 100644 arch/riscv/kernel/stacktrace.c
create mode 100644 arch/riscv/lib/memcpy.S
create mode 100644 arch/riscv/lib/memset.S
create mode 100644 arch/riscv/lib/uaccess.S
create mode 100644 arch/riscv/lib/udivdi3.S
diff --git a/arch/riscv/include/asm/asm.h b/arch/riscv/include/asm/asm.h
new file mode 100644
index 000000000000..6cbbb6a68d76
--- /dev/null
+++ b/arch/riscv/include/asm/asm.h
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2015 Regents of the University of California
+ *
+ * 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, version 2.
+ *
+ * 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.
+ */
+
+#ifndef _ASM_RISCV_ASM_H
+#define _ASM_RISCV_ASM_H
+
+#ifdef __ASSEMBLY__
+#define __ASM_STR(x) x
+#else
+#define __ASM_STR(x) #x
+#endif
+
+#if __riscv_xlen == 64
+#define __REG_SEL(a, b) __ASM_STR(a)
+#elif __riscv_xlen == 32
+#define __REG_SEL(a, b) __ASM_STR(b)
+#else
+#error "Unexpected __riscv_xlen"
+#endif
+
+#define REG_L __REG_SEL(ld, lw)
+#define REG_S __REG_SEL(sd, sw)
+#define SZREG __REG_SEL(8, 4)
+#define LGREG __REG_SEL(3, 2)
+
+#if __SIZEOF_POINTER__ == 8
+#ifdef __ASSEMBLY__
+#define RISCV_PTR .dword
+#define RISCV_SZPTR 8
+#define RISCV_LGPTR 3
+#else
+#define RISCV_PTR ".dword"
+#define RISCV_SZPTR "8"
+#define RISCV_LGPTR "3"
+#endif
+#elif __SIZEOF_POINTER__ == 4
+#ifdef __ASSEMBLY__
+#define RISCV_PTR .word
+#define RISCV_SZPTR 4
+#define RISCV_LGPTR 2
+#else
+#define RISCV_PTR ".word"
+#define RISCV_SZPTR "4"
+#define RISCV_LGPTR "2"
+#endif
+#else
+#error "Unexpected __SIZEOF_POINTER__"
+#endif
+
+#if (__SIZEOF_INT__ == 4)
+#define INT __ASM_STR(.word)
+#define SZINT __ASM_STR(4)
+#define LGINT __ASM_STR(2)
+#else
+#error "Unexpected __SIZEOF_INT__"
+#endif
+
+#if (__SIZEOF_SHORT__ == 2)
+#define SHORT __ASM_STR(.half)
+#define SZSHORT __ASM_STR(2)
+#define LGSHORT __ASM_STR(1)
+#else
+#error "Unexpected __SIZEOF_SHORT__"
+#endif
+
+#endif /* _ASM_RISCV_ASM_H */
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
new file mode 100644
index 000000000000..387d0dbf0073
--- /dev/null
+++ b/arch/riscv/include/asm/csr.h
@@ -0,0 +1,125 @@
+/*
+ * Copyright (C) 2015 Regents of the University of California
+ *
+ * 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, version 2.
+ *
+ * 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.
+ */
+
+#ifndef _ASM_RISCV_CSR_H
+#define _ASM_RISCV_CSR_H
+
+#include <linux/const.h>
+
+/* Status register flags */
+#define SR_IE _AC(0x00000002, UL) /* Interrupt Enable */
+#define SR_PIE _AC(0x00000020, UL) /* Previous IE */
+#define SR_PS _AC(0x00000100, UL) /* Previously Supervisor */
+#define SR_SUM _AC(0x00040000, UL) /* Supervisor may access User Memory */
+
+#define SR_FS _AC(0x00006000, UL) /* Floating-point Status */
+#define SR_FS_OFF _AC(0x00000000, UL)
+#define SR_FS_INITIAL _AC(0x00002000, UL)
+#define SR_FS_CLEAN _AC(0x00004000, UL)
+#define SR_FS_DIRTY _AC(0x00006000, UL)
+
+#define SR_XS _AC(0x00018000, UL) /* Extension Status */
+#define SR_XS_OFF _AC(0x00000000, UL)
+#define SR_XS_INITIAL _AC(0x00008000, UL)
+#define SR_XS_CLEAN _AC(0x00010000, UL)
+#define SR_XS_DIRTY _AC(0x00018000, UL)
+
+#ifndef CONFIG_64BIT
+#define SR_SD _AC(0x80000000, UL) /* FS/XS dirty */
+#else
+#define SR_SD _AC(0x8000000000000000, UL) /* FS/XS dirty */
+#endif
+
+/* SPTBR flags */
+#if __riscv_xlen == 32
+#define SPTBR_PPN _AC(0x003FFFFF, UL)
+#define SPTBR_MODE_32 _AC(0x80000000, UL)
+#define SPTBR_MODE SPTBR_MODE_32
+#else
+#define SPTBR_PPN _AC(0x00000FFFFFFFFFFF, UL)
+#define SPTBR_MODE_39 _AC(0x8000000000000000, UL)
+#define SPTBR_MODE SPTBR_MODE_39
+#endif
+
+/* Interrupt Enable and Interrupt Pending flags */
+#define SIE_SSIE _AC(0x00000002, UL) /* Software Interrupt Enable */
+#define SIE_STIE _AC(0x00000020, UL) /* Timer Interrupt Enable */
+
+#define EXC_INST_MISALIGNED 0
+#define EXC_INST_ACCESS 1
+#define EXC_BREAKPOINT 3
+#define EXC_LOAD_ACCESS 5
+#define EXC_STORE_ACCESS 7
+#define EXC_SYSCALL 8
+#define EXC_INST_PAGE_FAULT 12
+#define EXC_LOAD_PAGE_FAULT 13
+#define EXC_STORE_PAGE_FAULT 15
+
+#ifndef __ASSEMBLY__
+
+#define csr_swap(csr, val) \
+({ \
+ unsigned long __v = (unsigned long)(val); \
+ __asm__ __volatile__ ("csrrw %0, " #csr ", %1" \
+ : "=r" (__v) : "rK" (__v)); \
+ __v; \
+})
+
+#define csr_read(csr) \
+({ \
+ register unsigned long __v; \
+ __asm__ __volatile__ ("csrr %0, " #csr \
+ : "=r" (__v)); \
+ __v; \
+})
+
+#define csr_write(csr, val) \
+({ \
+ unsigned long __v = (unsigned long)(val); \
+ __asm__ __volatile__ ("csrw " #csr ", %0" \
+ : : "rK" (__v)); \
+})
+
+#define csr_read_set(csr, val) \
+({ \
+ unsigned long __v = (unsigned long)(val); \
+ __asm__ __volatile__ ("csrrs %0, " #csr ", %1" \
+ : "=r" (__v) : "rK" (__v)); \
+ __v; \
+})
+
+#define csr_set(csr, val) \
+({ \
+ unsigned long __v = (unsigned long)(val); \
+ __asm__ __volatile__ ("csrs " #csr ", %0" \
+ : : "rK" (__v)); \
+})
+
+#define csr_read_clear(csr, val) \
+({ \
+ unsigned long __v = (unsigned long)(val); \
+ __asm__ __volatile__ ("csrrc %0, " #csr ", %1" \
+ : "=r" (__v) : "rK" (__v)); \
+ __v; \
+})
+
+#define csr_clear(csr, val) \
+({ \
+ unsigned long __v = (unsigned long)(val); \
+ __asm__ __volatile__ ("csrc " #csr ", %0" \
+ : : "rK" (__v)); \
+})
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* _ASM_RISCV_CSR_H */
diff --git a/arch/riscv/include/asm/linkage.h b/arch/riscv/include/asm/linkage.h
new file mode 100644
index 000000000000..b7b304ca89c4
--- /dev/null
+++ b/arch/riscv/include/asm/linkage.h
@@ -0,0 +1,20 @@
+/*
+ * Copyright (C) 2015 Regents of the University of California
+ *
+ * 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, version 2.
+ *
+ * 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.
+ */
+
+#ifndef _ASM_RISCV_LINKAGE_H
+#define _ASM_RISCV_LINKAGE_H
+
+#define __ALIGN .balign 4
+#define __ALIGN_STR ".balign 4"
+
+#endif /* _ASM_RISCV_LINKAGE_H */
diff --git a/arch/riscv/include/asm/string.h b/arch/riscv/include/asm/string.h
new file mode 100644
index 000000000000..1c59cf4e8ccc
--- /dev/null
+++ b/arch/riscv/include/asm/string.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2013 Regents of the University of California
+ *
+ * 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, version 2.
+ *
+ * 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.
+ */
+
+#ifndef _ASM_RISCV_STRING_H
+#define _ASM_RISCV_STRING_H
+
+#ifdef __KERNEL__
+
+#include <linux/types.h>
+#include <linux/linkage.h>
+
+#define __HAVE_ARCH_MEMSET
+extern asmlinkage void *memset(void *, int, size_t);
+
+#define __HAVE_ARCH_MEMCPY
+extern asmlinkage void *memcpy(void *, const void *, size_t);
+
+#endif /* __KERNEL__ */
+
+#endif /* _ASM_RISCV_STRING_H */
diff --git a/arch/riscv/include/asm/uaccess.h b/arch/riscv/include/asm/uaccess.h
new file mode 100644
index 000000000000..f3ece74219d7
--- /dev/null
+++ b/arch/riscv/include/asm/uaccess.h
@@ -0,0 +1,440 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ * 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, version 2.
+ *
+ * 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.
+ *
+ * This file was copied from include/asm-generic/uaccess.h
+ */
+
+#ifndef _ASM_RISCV_UACCESS_H
+#define _ASM_RISCV_UACCESS_H
+
+/*
+ * User space memory access functions
+ */
+#include <linux/errno.h>
+#include <linux/compiler.h>
+#include <linux/thread_info.h>
+#include <asm/byteorder.h>
+#include <asm/asm.h>
+
+#ifdef CONFIG_RV_PUM
+#define __enable_user_access() \
+ __asm__ __volatile__ ("csrs sstatus, %0" : : "r" (SR_SUM) : "memory")
+#define __disable_user_access() \
+ __asm__ __volatile__ ("csrc sstatus, %0" : : "r" (SR_SUM) : "memory")
+#else
+#define __enable_user_access()
+#define __disable_user_access()
+#endif
+
+/*
+ * The fs value determines whether argument validity checking should be
+ * performed or not. If get_fs() == USER_DS, checking is performed, with
+ * get_fs() == KERNEL_DS, checking is bypassed.
+ *
+ * For historical reasons, these macros are grossly misnamed.
+ */
+
+#define KERNEL_DS (~0UL)
+#define USER_DS (TASK_SIZE)
+
+#define get_ds() (KERNEL_DS)
+#define get_fs() (current_thread_info()->addr_limit)
+
+static inline void set_fs(mm_segment_t fs)
+{
+ current_thread_info()->addr_limit = fs;
+}
+
+#define segment_eq(a, b) ((a) == (b))
+
+#define user_addr_max() (get_fs())
+
+
+#define VERIFY_READ 0
+#define VERIFY_WRITE 1
+
+/**
+ * access_ok: - Checks if a user space pointer is valid
+ * @type: Type of access: %VERIFY_READ or %VERIFY_WRITE. Note that
+ * %VERIFY_WRITE is a superset of %VERIFY_READ - if it is safe
+ * to write to a block, it is always safe to read from it.
+ * @addr: User space pointer to start of block to check
+ * @size: Size of block to check
+ *
+ * Context: User context only. This function may sleep.
+ *
+ * Checks if a pointer to a block of memory in user space is valid.
+ *
+ * Returns true (nonzero) if the memory block may be valid, false (zero)
+ * if it is definitely invalid.
+ *
+ * Note that, depending on architecture, this function probably just
+ * checks that the pointer is in the user space range - after calling
+ * this function, memory access functions may still return -EFAULT.
+ */
+#define access_ok(type, addr, size) ({ \
+ __chk_user_ptr(addr); \
+ likely(__access_ok((unsigned long __force)(addr), (size))); \
+})
+
+/* Ensure that the range [addr, addr+size) is within the process's
+ * address space
+ */
+static inline int __access_ok(unsigned long addr, unsigned long size)
+{
+ const mm_segment_t fs = get_fs();
+
+ return (size <= fs) && (addr <= (fs - size));
+}
+
+/*
+ * The exception table consists of pairs of addresses: the first is the
+ * address of an instruction that is allowed to fault, and the second is
+ * the address at which the program should continue. No registers are
+ * modified, so it is entirely up to the continuation code to figure out
+ * what to do.
+ *
+ * All the routines below use bits of fixup code that are out of line
+ * with the main instruction path. This means when everything is well,
+ * we don't even have to jump over them. Further, they do not intrude
+ * on our cache or tlb entries.
+ */
+
+struct exception_table_entry {
+ unsigned long insn, fixup;
+};
+
+extern int fixup_exception(struct pt_regs *state);
+
+#if defined(__LITTLE_ENDIAN)
+#define __MSW 1
+#define __LSW 0
+#elif defined(__BIG_ENDIAN)
+#define __MSW 0
+#define __LSW 1
+#else
+#error "Unknown endianness"
+#endif
+
+/*
+ * The "__xxx" versions of the user access functions do not verify the address
+ * space - it must have been done previously with a separate "access_ok()"
+ * call.
+ */
+
+#ifdef CONFIG_MMU
+#define __get_user_asm(insn, x, ptr, err) \
+do { \
+ uintptr_t __tmp; \
+ __typeof__(x) __x; \
+ __enable_user_access(); \
+ __asm__ __volatile__ ( \
+ "1:\n" \
+ " " insn " %1, %3\n" \
+ "2:\n" \
+ " .section .fixup,\"ax\"\n" \
+ " .balign 4\n" \
+ "3:\n" \
+ " li %0, %4\n" \
+ " li %1, 0\n" \
+ " jump 2b, %2\n" \
+ " .previous\n" \
+ " .section __ex_table,\"a\"\n" \
+ " .balign " RISCV_SZPTR "\n" \
+ " " RISCV_PTR " 1b, 3b\n" \
+ " .previous" \
+ : "+r" (err), "=&r" (__x), "=r" (__tmp) \
+ : "m" (*(ptr)), "i" (-EFAULT)); \
+ __disable_user_access(); \
+ (x) = __x; \
+} while (0)
+#endif /* CONFIG_MMU */
+
+#ifdef CONFIG_64BIT
+#define __get_user_8(x, ptr, err) \
+ __get_user_asm("ld", x, ptr, err)
+#else /* !CONFIG_64BIT */
+#ifdef CONFIG_MMU
+#define __get_user_8(x, ptr, err) \
+do { \
+ u32 __user *__ptr = (u32 __user *)(ptr); \
+ u32 __lo, __hi; \
+ uintptr_t __tmp; \
+ __enable_user_access(); \
+ __asm__ __volatile__ ( \
+ "1:\n" \
+ " lw %1, %4\n" \
+ "2:\n" \
+ " lw %2, %5\n" \
+ "3:\n" \
+ " .section .fixup,\"ax\"\n" \
+ " .balign 4\n" \
+ "4:\n" \
+ " li %0, %6\n" \
+ " li %1, 0\n" \
+ " li %2, 0\n" \
+ " jump 3b, %3\n" \
+ " .previous\n" \
+ " .section __ex_table,\"a\"\n" \
+ " .balign " RISCV_SZPTR "\n" \
+ " " RISCV_PTR " 1b, 4b\n" \
+ " " RISCV_PTR " 2b, 4b\n" \
+ " .previous" \
+ : "+r" (err), "=&r" (__lo), "=r" (__hi), \
+ "=r" (__tmp) \
+ : "m" (__ptr[__LSW]), "m" (__ptr[__MSW]), \
+ "i" (-EFAULT)); \
+ __disable_user_access(); \
+ (x) = (__typeof__(x))((__typeof__((x)-(x)))( \
+ (((u64)__hi << 32) | __lo))); \
+} while (0)
+#endif /* CONFIG_MMU */
+#endif /* CONFIG_64BIT */
+
+
+/**
+ * __get_user: - Get a simple variable from user space, with less checking.
+ * @x: Variable to store result.
+ * @ptr: Source address, in user space.
+ *
+ * Context: User context only. This function may sleep.
+ *
+ * This macro copies a single simple variable from user space to kernel
+ * space. It supports simple types like char and int, but not larger
+ * data types like structures or arrays.
+ *
+ * @ptr must have pointer-to-simple-variable type, and the result of
+ * dereferencing @ptr must be assignable to @x without a cast.
+ *
+ * Caller must check the pointer with access_ok() before calling this
+ * function.
+ *
+ * Returns zero on success, or -EFAULT on error.
+ * On error, the variable @x is set to zero.
+ */
+#define __get_user(x, ptr) \
+({ \
+ register long __gu_err = 0; \
+ const __typeof__(*(ptr)) __user *__gu_ptr = (ptr); \
+ __chk_user_ptr(__gu_ptr); \
+ switch (sizeof(*__gu_ptr)) { \
+ case 1: \
+ __get_user_asm("lb", (x), __gu_ptr, __gu_err); \
+ break; \
+ case 2: \
+ __get_user_asm("lh", (x), __gu_ptr, __gu_err); \
+ break; \
+ case 4: \
+ __get_user_asm("lw", (x), __gu_ptr, __gu_err); \
+ break; \
+ case 8: \
+ __get_user_8((x), __gu_ptr, __gu_err); \
+ break; \
+ default: \
+ BUILD_BUG(); \
+ } \
+ __gu_err; \
+})
+
+/**
+ * get_user: - Get a simple variable from user space.
+ * @x: Variable to store result.
+ * @ptr: Source address, in user space.
+ *
+ * Context: User context only. This function may sleep.
+ *
+ * This macro copies a single simple variable from user space to kernel
+ * space. It supports simple types like char and int, but not larger
+ * data types like structures or arrays.
+ *
+ * @ptr must have pointer-to-simple-variable type, and the result of
+ * dereferencing @ptr must be assignable to @x without a cast.
+ *
+ * Returns zero on success, or -EFAULT on error.
+ * On error, the variable @x is set to zero.
+ */
+#define get_user(x, ptr) \
+({ \
+ const __typeof__(*(ptr)) __user *__p = (ptr); \
+ might_fault(); \
+ access_ok(VERIFY_READ, __p, sizeof(*__p)) ? \
+ __get_user((x), __p) : \
+ ((x) = 0, -EFAULT); \
+})
+
+
+#ifdef CONFIG_MMU
+#define __put_user_asm(insn, x, ptr, err) \
+do { \
+ uintptr_t __tmp; \
+ __typeof__(*(ptr)) __x = x; \
+ __enable_user_access(); \
+ __asm__ __volatile__ ( \
+ "1:\n" \
+ " " insn " %z3, %2\n" \
+ "2:\n" \
+ " .section .fixup,\"ax\"\n" \
+ " .balign 4\n" \
+ "3:\n" \
+ " li %0, %4\n" \
+ " jump 2b, %1\n" \
+ " .previous\n" \
+ " .section __ex_table,\"a\"\n" \
+ " .balign " RISCV_SZPTR "\n" \
+ " " RISCV_PTR " 1b, 3b\n" \
+ " .previous" \
+ : "+r" (err), "=r" (__tmp), "=m" (*(ptr)) \
+ : "rJ" (__x), "i" (-EFAULT)); \
+ __disable_user_access(); \
+} while (0)
+#endif /* CONFIG_MMU */
+
+
+#ifdef CONFIG_64BIT
+#define __put_user_8(x, ptr, err) \
+ __put_user_asm("sd", x, ptr, err)
+#else /* !CONFIG_64BIT */
+#ifdef CONFIG_MMU
+#define __put_user_8(x, ptr, err) \
+do { \
+ u32 __user *__ptr = (u32 __user *)(ptr); \
+ u64 __x = (__typeof__((x)-(x)))(x); \
+ uintptr_t __tmp; \
+ __enable_user_access(); \
+ __asm__ __volatile__ ( \
+ "1:\n" \
+ " sw %z4, %2\n" \
+ "2:\n" \
+ " sw %z5, %3\n" \
+ "3:\n" \
+ " .section .fixup,\"ax\"\n" \
+ " .balign 4\n" \
+ "4:\n" \
+ " li %0, %6\n" \
+ " jump 2b, %1\n" \
+ " .previous\n" \
+ " .section __ex_table,\"a\"\n" \
+ " .balign " RISCV_SZPTR "\n" \
+ " " RISCV_PTR " 1b, 4b\n" \
+ " " RISCV_PTR " 2b, 4b\n" \
+ " .previous" \
+ : "+r" (err), "=r" (__tmp), \
+ "=m" (__ptr[__LSW]), \
+ "=m" (__ptr[__MSW]) \
+ : "rJ" (__x), "rJ" (__x >> 32), "i" (-EFAULT)); \
+ __disable_user_access(); \
+} while (0)
+#endif /* CONFIG_MMU */
+#endif /* CONFIG_64BIT */
+
+
+/**
+ * __put_user: - Write a simple value into user space, with less checking.
+ * @x: Value to copy to user space.
+ * @ptr: Destination address, in user space.
+ *
+ * Context: User context only. This function may sleep.
+ *
+ * This macro copies a single simple value from kernel space to user
+ * space. It supports simple types like char and int, but not larger
+ * data types like structures or arrays.
+ *
+ * @ptr must have pointer-to-simple-variable type, and @x must be assignable
+ * to the result of dereferencing @ptr.
+ *
+ * Caller must check the pointer with access_ok() before calling this
+ * function.
+ *
+ * Returns zero on success, or -EFAULT on error.
+ */
+#define __put_user(x, ptr) \
+({ \
+ register long __pu_err = 0; \
+ __typeof__(*(ptr)) __user *__gu_ptr = (ptr); \
+ __chk_user_ptr(__gu_ptr); \
+ switch (sizeof(*__gu_ptr)) { \
+ case 1: \
+ __put_user_asm("sb", (x), __gu_ptr, __pu_err); \
+ break; \
+ case 2: \
+ __put_user_asm("sh", (x), __gu_ptr, __pu_err); \
+ break; \
+ case 4: \
+ __put_user_asm("sw", (x), __gu_ptr, __pu_err); \
+ break; \
+ case 8: \
+ __put_user_8((x), __gu_ptr, __pu_err); \
+ break; \
+ default: \
+ BUILD_BUG(); \
+ } \
+ __pu_err; \
+})
+
+/**
+ * put_user: - Write a simple value into user space.
+ * @x: Value to copy to user space.
+ * @ptr: Destination address, in user space.
+ *
+ * Context: User context only. This function may sleep.
+ *
+ * This macro copies a single simple value from kernel space to user
+ * space. It supports simple types like char and int, but not larger
+ * data types like structures or arrays.
+ *
+ * @ptr must have pointer-to-simple-variable type, and @x must be assignable
+ * to the result of dereferencing @ptr.
+ *
+ * Returns zero on success, or -EFAULT on error.
+ */
+#define put_user(x, ptr) \
+({ \
+ __typeof__(*(ptr)) __user *__p = (ptr); \
+ might_fault(); \
+ access_ok(VERIFY_WRITE, __p, sizeof(*__p)) ? \
+ __put_user((x), __p) : \
+ -EFAULT; \
+})
+
+
+extern unsigned long __must_check __copy_user(void __user *to,
+ const void __user *from, unsigned long n);
+
+static inline unsigned long
+raw_copy_from_user(void *to, const void __user *from, unsigned long n)
+{
+ return __copy_user(to, from, n);
+}
+
+static inline unsigned long
+raw_copy_to_user(void __user *to, const void *from, unsigned long n)
+{
+ return __copy_user(to, from, n);
+}
+
+extern long strncpy_from_user(char *dest, const char __user *src, long count);
+
+extern long __must_check strlen_user(const char __user *str);
+extern long __must_check strnlen_user(const char __user *str, long n);
+
+extern
+unsigned long __must_check __clear_user(void __user *addr, unsigned long n);
+
+static inline
+unsigned long __must_check clear_user(void __user *to, unsigned long n)
+{
+ might_fault();
+ return access_ok(VERIFY_WRITE, to, n) ?
+ __clear_user(to, n) : n;
+}
+
+#endif /* _ASM_RISCV_UACCESS_H */
diff --git a/arch/riscv/include/asm/word-at-a-time.h b/arch/riscv/include/asm/word-at-a-time.h
new file mode 100644
index 000000000000..aa6238791d3e
--- /dev/null
+++ b/arch/riscv/include/asm/word-at-a-time.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2012 Regents of the University of California
+ *
+ * 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, version 2.
+ *
+ * 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.
+ * Derived from arch/x86/include/asm/word-at-a-time.h
+ */
+
+#ifndef _ASM_RISCV_WORD_AT_A_TIME_H
+#define _ASM_RISCV_WORD_AT_A_TIME_H
+
+
+#include <linux/kernel.h>
+
+struct word_at_a_time {
+ const unsigned long one_bits, high_bits;
+};
+
+#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
+
+static inline unsigned long has_zero(unsigned long val,
+ unsigned long *bits, const struct word_at_a_time *c)
+{
+ unsigned long mask = ((val - c->one_bits) & ~val) & c->high_bits;
+ *bits = mask;
+ return mask;
+}
+
+static inline unsigned long prep_zero_mask(unsigned long val,
+ unsigned long bits, const struct word_at_a_time *c)
+{
+ return bits;
+}
+
+static inline unsigned long create_zero_mask(unsigned long bits)
+{
+ bits = (bits - 1) & ~bits;
+ return bits >> 7;
+}
+
+static inline unsigned long find_zero(unsigned long mask)
+{
+ return fls64(mask) >> 3;
+}
+
+/* The mask we created is directly usable as a bytemask */
+#define zero_bytemask(mask) (mask)
+
+#endif /* _ASM_RISCV_WORD_AT_A_TIME_H */
diff --git a/arch/riscv/kernel/stacktrace.c b/arch/riscv/kernel/stacktrace.c
new file mode 100644
index 000000000000..109f5120d5c7
--- /dev/null
+++ b/arch/riscv/kernel/stacktrace.c
@@ -0,0 +1,177 @@
+/*
+ * Copyright (C) 2008 ARM Limited
+ * Copyright (C) 2014 Regents of the University of California
+ *
+ * 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.
+ */
+
+#include <linux/export.h>
+#include <linux/kallsyms.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/sched/task_stack.h>
+#include <linux/stacktrace.h>
+
+#ifdef CONFIG_FRAME_POINTER
+
+struct stackframe {
+ unsigned long fp;
+ unsigned long ra;
+};
+
+static void notrace walk_stackframe(struct task_struct *task,
+ struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
+{
+ unsigned long fp, sp, pc;
+
+ if (regs) {
+ fp = GET_FP(regs);
+ sp = GET_USP(regs);
+ pc = GET_IP(regs);
+ } else if (task == NULL || task == current) {
+ const register unsigned long current_sp __asm__ ("sp");
+ fp = (unsigned long)__builtin_frame_address(0);
+ sp = current_sp;
+ pc = (unsigned long)walk_stackframe;
+ } else {
+ /* task blocked in __switch_to */
+ fp = task->thread.s[0];
+ sp = task->thread.sp;
+ pc = task->thread.ra;
+ }
+
+ for (;;) {
+ unsigned long low, high;
+ struct stackframe *frame;
+
+ if (unlikely(!__kernel_text_address(pc) || fn(pc, arg)))
+ break;
+
+ /* Validate frame pointer */
+ low = sp + sizeof(struct stackframe);
+ high = ALIGN(sp, THREAD_SIZE);
+ if (unlikely(fp < low || fp > high || fp & 0x7))
+ break;
+ /* Unwind stack frame */
+ frame = (struct stackframe *)fp - 1;
+ sp = fp;
+ fp = frame->fp;
+ pc = frame->ra - 0x4;
+ }
+}
+
+#else /* !CONFIG_FRAME_POINTER */
+
+static void notrace walk_stackframe(struct task_struct *task,
+ struct pt_regs *regs, bool (*fn)(unsigned long, void *), void *arg)
+{
+ unsigned long sp, pc;
+ unsigned long *ksp;
+
+ if (regs) {
+ sp = GET_USP(regs);
+ pc = GET_IP(regs);
+ } else if (task == NULL || task == current) {
+ const register unsigned long current_sp __asm__ ("sp");
+ sp = current_sp;
+ pc = (unsigned long)walk_stackframe;
+ } else {
+ /* task blocked in __switch_to */
+ sp = task->thread.sp;
+ pc = task->thread.ra;
+ }
+
+ if (unlikely(sp & 0x7))
+ return;
+
+ ksp = (unsigned long *)sp;
+ while (!kstack_end(ksp)) {
+ if (__kernel_text_address(pc) && unlikely(fn(pc, arg)))
+ break;
+ pc = (*ksp++) - 0x4;
+ }
+}
+
+#endif /* CONFIG_FRAME_POINTER */
+
+
+static bool print_trace_address(unsigned long pc, void *arg)
+{
+ print_ip_sym(pc);
+ return false;
+}
+
+void show_stack(struct task_struct *task, unsigned long *sp)
+{
+ printk("Call Trace:\n");
+ walk_stackframe(task, NULL, print_trace_address, NULL);
+}
+
+
+static bool save_wchan(unsigned long pc, void *arg)
+{
+ if (!in_sched_functions(pc)) {
+ unsigned long *p = arg;
+ *p = pc;
+ return true;
+ }
+ return false;
+}
+
+unsigned long get_wchan(struct task_struct *task)
+{
+ unsigned long pc = 0;
+
+ if (likely(task && task != current && task->state != TASK_RUNNING))
+ walk_stackframe(task, NULL, save_wchan, &pc);
+ return pc;
+}
+
+
+#ifdef CONFIG_STACKTRACE
+
+static bool __save_trace(unsigned long pc, void *arg, bool nosched)
+{
+ struct stack_trace *trace = arg;
+
+ if (unlikely(nosched && in_sched_functions(pc)))
+ return false;
+ if (unlikely(trace->skip > 0)) {
+ trace->skip--;
+ return false;
+ }
+
+ trace->entries[trace->nr_entries++] = pc;
+ return (trace->nr_entries >= trace->max_entries);
+}
+
+static bool save_trace(unsigned long pc, void *arg)
+{
+ return __save_trace(pc, arg, false);
+}
+
+/*
+ * Save stack-backtrace addresses into a stack_trace buffer.
+ */
+void save_stack_trace_tsk(struct task_struct *tsk, struct stack_trace *trace)
+{
+ walk_stackframe(tsk, NULL, save_trace, trace);
+ if (trace->nr_entries < trace->max_entries)
+ trace->entries[trace->nr_entries++] = ULONG_MAX;
+}
+EXPORT_SYMBOL_GPL(save_stack_trace_tsk);
+
+void save_stack_trace(struct stack_trace *trace)
+{
+ save_stack_trace_tsk(NULL, trace);
+}
+EXPORT_SYMBOL_GPL(save_stack_trace);
+
+#endif /* CONFIG_STACKTRACE */
diff --git a/arch/riscv/lib/memcpy.S b/arch/riscv/lib/memcpy.S
new file mode 100644
index 000000000000..5b576cf041eb
--- /dev/null
+++ b/arch/riscv/lib/memcpy.S
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2013 Regents of the University of California
+ *
+ * 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, version 2.
+ *
+ * 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.
+ */
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+
+/* void *memcpy(void *, const void *, size_t) */
+ENTRY(memcpy)
+ move t6, a0 /* Preserve return value */
+
+ /* Defer to byte-oriented copy for small sizes */
+ sltiu a3, a2, 128
+ bnez a3, 4f
+ /* Use word-oriented copy only if low-order bits match */
+ andi a3, t6, SZREG-1
+ andi a4, a1, SZREG-1
+ bne a3, a4, 4f
+
+ beqz a3, 2f /* Skip if already aligned */
+ /* Round to nearest double word-aligned address
+ greater than or equal to start address */
+ andi a3, a1, ~(SZREG-1)
+ addi a3, a3, SZREG
+ /* Handle initial misalignment */
+ sub a4, a3, a1
+1:
+ lb a5, 0(a1)
+ addi a1, a1, 1
+ sb a5, 0(t6)
+ addi t6, t6, 1
+ bltu a1, a3, 1b
+ sub a2, a2, a4 /* Update count */
+
+2:
+ andi a4, a2, ~((16*SZREG)-1)
+ beqz a4, 4f
+ add a3, a1, a4
+3:
+ REG_L a4, 0(a1)
+ REG_L a5, SZREG(a1)
+ REG_L a6, 2*SZREG(a1)
+ REG_L a7, 3*SZREG(a1)
+ REG_L t0, 4*SZREG(a1)
+ REG_L t1, 5*SZREG(a1)
+ REG_L t2, 6*SZREG(a1)
+ REG_L t3, 7*SZREG(a1)
+ REG_L t4, 8*SZREG(a1)
+ REG_L t5, 9*SZREG(a1)
+ REG_S a4, 0(t6)
+ REG_S a5, SZREG(t6)
+ REG_S a6, 2*SZREG(t6)
+ REG_S a7, 3*SZREG(t6)
+ REG_S t0, 4*SZREG(t6)
+ REG_S t1, 5*SZREG(t6)
+ REG_S t2, 6*SZREG(t6)
+ REG_S t3, 7*SZREG(t6)
+ REG_S t4, 8*SZREG(t6)
+ REG_S t5, 9*SZREG(t6)
+ REG_L a4, 10*SZREG(a1)
+ REG_L a5, 11*SZREG(a1)
+ REG_L a6, 12*SZREG(a1)
+ REG_L a7, 13*SZREG(a1)
+ REG_L t0, 14*SZREG(a1)
+ REG_L t1, 15*SZREG(a1)
+ addi a1, a1, 16*SZREG
+ REG_S a4, 10*SZREG(t6)
+ REG_S a5, 11*SZREG(t6)
+ REG_S a6, 12*SZREG(t6)
+ REG_S a7, 13*SZREG(t6)
+ REG_S t0, 14*SZREG(t6)
+ REG_S t1, 15*SZREG(t6)
+ addi t6, t6, 16*SZREG
+ bltu a1, a3, 3b
+ andi a2, a2, (16*SZREG)-1 /* Update count */
+
+4:
+ /* Handle trailing misalignment */
+ beqz a2, 6f
+ add a3, a1, a2
+5:
+ lb a4, 0(a1)
+ addi a1, a1, 1
+ sb a4, 0(t6)
+ addi t6, t6, 1
+ bltu a1, a3, 5b
+6:
+ ret
+END(memcpy)
diff --git a/arch/riscv/lib/memset.S b/arch/riscv/lib/memset.S
new file mode 100644
index 000000000000..d83c38099653
--- /dev/null
+++ b/arch/riscv/lib/memset.S
@@ -0,0 +1,118 @@
+/*
+ * Copyright (C) 2013 Regents of the University of California
+ *
+ * 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, version 2.
+ *
+ * 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.
+ */
+
+
+#include <linux/linkage.h>
+#include <asm/asm.h>
+
+/* void *memset(void *, int, size_t) */
+ENTRY(memset)
+ move t0, a0 /* Preserve return value */
+
+ /* Defer to byte-oriented fill for small sizes */
+ sltiu a3, a2, 16
+ bnez a3, 4f
+
+ /* Round to nearest XLEN-aligned address
+ greater than or equal to start address */
+ addi a3, t0, SZREG-1
+ andi a3, a3, ~(SZREG-1)
+ beq a3, t0, 2f /* Skip if already aligned */
+ /* Handle initial misalignment */
+ sub a4, a3, t0
+1:
+ sb a1, 0(t0)
+ addi t0, t0, 1
+ bltu t0, a3, 1b
+ sub a2, a2, a4 /* Update count */
+
+2: /* Duff's device with 32 XLEN stores per iteration */
+ /* Broadcast value into all bytes */
+ andi a1, a1, 0xff
+ slli a3, a1, 8
+ or a1, a3, a1
+ slli a3, a1, 16
+ or a1, a3, a1
+#ifdef CONFIG_64BIT
+ slli a3, a1, 32
+ or a1, a3, a1
+#endif
+
+ /* Calculate end address */
+ andi a4, a2, ~(SZREG-1)
+ add a3, t0, a4
+
+ andi a4, a4, 31*SZREG /* Calculate remainder */
+ beqz a4, 3f /* Shortcut if no remainder */
+ neg a4, a4
+ addi a4, a4, 32*SZREG /* Calculate initial offset */
+
+ /* Adjust start address with offset */
+ sub t0, t0, a4
+
+ /* Jump into loop body */
+ /* Assumes 32-bit instruction lengths */
+ la a5, 3f
+#ifdef CONFIG_64BIT
+ srli a4, a4, 1
+#endif
+ add a5, a5, a4
+ jr a5
+3:
+ REG_S a1, 0(t0)
+ REG_S a1, SZREG(t0)
+ REG_S a1, 2*SZREG(t0)
+ REG_S a1, 3*SZREG(t0)
+ REG_S a1, 4*SZREG(t0)
+ REG_S a1, 5*SZREG(t0)
+ REG_S a1, 6*SZREG(t0)
+ REG_S a1, 7*SZREG(t0)
+ REG_S a1, 8*SZREG(t0)
+ REG_S a1, 9*SZREG(t0)
+ REG_S a1, 10*SZREG(t0)
+ REG_S a1, 11*SZREG(t0)
+ REG_S a1, 12*SZREG(t0)
+ REG_S a1, 13*SZREG(t0)
+ REG_S a1, 14*SZREG(t0)
+ REG_S a1, 15*SZREG(t0)
+ REG_S a1, 16*SZREG(t0)
+ REG_S a1, 17*SZREG(t0)
+ REG_S a1, 18*SZREG(t0)
+ REG_S a1, 19*SZREG(t0)
+ REG_S a1, 20*SZREG(t0)
+ REG_S a1, 21*SZREG(t0)
+ REG_S a1, 22*SZREG(t0)
+ REG_S a1, 23*SZREG(t0)
+ REG_S a1, 24*SZREG(t0)
+ REG_S a1, 25*SZREG(t0)
+ REG_S a1, 26*SZREG(t0)
+ REG_S a1, 27*SZREG(t0)
+ REG_S a1, 28*SZREG(t0)
+ REG_S a1, 29*SZREG(t0)
+ REG_S a1, 30*SZREG(t0)
+ REG_S a1, 31*SZREG(t0)
+ addi t0, t0, 32*SZREG
+ bltu t0, a3, 3b
+ andi a2, a2, SZREG-1 /* Update count */
+
+4:
+ /* Handle trailing misalignment */
+ beqz a2, 6f
+ add a3, t0, a2
+5:
+ sb a1, 0(t0)
+ addi t0, t0, 1
+ bltu t0, a3, 5b
+6:
+ ret
+END(memset)
diff --git a/arch/riscv/lib/uaccess.S b/arch/riscv/lib/uaccess.S
new file mode 100644
index 000000000000..cba994696aff
--- /dev/null
+++ b/arch/riscv/lib/uaccess.S
@@ -0,0 +1,125 @@
+#include <linux/linkage.h>
+#include <asm/asm.h>
+#include <asm/csr.h>
+
+ .altmacro
+ .macro fixup op reg addr lbl
+ LOCAL _epc
+_epc:
+ \op \reg, \addr
+ .section __ex_table,"a"
+ .balign RISCV_SZPTR
+ RISCV_PTR _epc, \lbl
+ .previous
+ .endm
+
+ENTRY(__copy_user)
+
+#ifdef CONFIG_RV_PUM
+ /* Enable access to user memory */
+ li t6, SR_SUM
+ csrs sstatus, t6
+#endif
+
+ add a3, a1, a2
+ /* Use word-oriented copy only if low-order bits match */
+ andi t0, a0, SZREG-1
+ andi t1, a1, SZREG-1
+ bne t0, t1, 2f
+
+ addi t0, a1, SZREG-1
+ andi t1, a3, ~(SZREG-1)
+ andi t0, t0, ~(SZREG-1)
+ /* a3: terminal address of source region
+ * t0: lowest XLEN-aligned address in source
+ * t1: highest XLEN-aligned address in source
+ */
+ bgeu t0, t1, 2f
+ bltu a1, t0, 4f
+1:
+ fixup REG_L, t2, (a1), 10f
+ fixup REG_S, t2, (a0), 10f
+ addi a1, a1, SZREG
+ addi a0, a0, SZREG
+ bltu a1, t1, 1b
+2:
+ bltu a1, a3, 5f
+
+3:
+#ifdef CONFIG_RV_PUM
+ /* Disable access to user memory */
+ csrc sstatus, t6
+#endif
+ li a0, 0
+ ret
+4: /* Edge case: unalignment */
+ fixup lbu, t2, (a1), 10f
+ fixup sb, t2, (a0), 10f
+ addi a1, a1, 1
+ addi a0, a0, 1
+ bltu a1, t0, 4b
+ j 1b
+5: /* Edge case: remainder */
+ fixup lbu, t2, (a1), 10f
+ fixup sb, t2, (a0), 10f
+ addi a1, a1, 1
+ addi a0, a0, 1
+ bltu a1, a3, 5b
+ j 3b
+ENDPROC(__copy_user)
+
+
+ENTRY(__clear_user)
+
+#ifdef CONFIG_RV_PUM
+ /* Enable access to user memory */
+ li t6, SR_SUM
+ csrs sstatus, t6
+#endif
+
+ add a3, a0, a1
+ addi t0, a0, SZREG-1
+ andi t1, a3, ~(SZREG-1)
+ andi t0, t0, ~(SZREG-1)
+ /* a3: terminal address of target region
+ * t0: lowest doubleword-aligned address in target region
+ * t1: highest doubleword-aligned address in target region
+ */
+ bgeu t0, t1, 2f
+ bltu a0, t0, 4f
+1:
+ fixup REG_S, zero, (a0), 10f
+ addi a0, a0, SZREG
+ bltu a0, t1, 1b
+2:
+ bltu a0, a3, 5f
+
+3:
+#ifdef CONFIG_RV_PUM
+ /* Disable access to user memory */
+ csrc sstatus, t6
+#endif
+ li a0, 0
+ ret
+4: /* Edge case: unalignment */
+ fixup sb, zero, (a0), 10f
+ addi a0, a0, 1
+ bltu a0, t0, 4b
+ j 1b
+5: /* Edge case: remainder */
+ fixup sb, zero, (a0), 10f
+ addi a0, a0, 1
+ bltu a0, a3, 5b
+ j 3b
+ENDPROC(__clear_user)
+
+ .section .fixup,"ax"
+ .balign 4
+10:
+#ifdef CONFIG_RV_PUM
+ /* Disable access to user memory */
+ csrs sstatus, t6
+#endif
+ sub a0, a3, a0
+ ret
+ .previous
diff --git a/arch/riscv/lib/udivdi3.S b/arch/riscv/lib/udivdi3.S
new file mode 100644
index 000000000000..cb01ae5b181a
--- /dev/null
+++ b/arch/riscv/lib/udivdi3.S
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2016-2017 Free Software Foundation, Inc.
+ *
+ * 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, version 2.
+ *
+ * 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.
+ */
+
+ .globl __udivdi3
+__udivdi3:
+ mv a2, a1
+ mv a1, a0
+ li a0, -1
+ beqz a2, .L5
+ li a3, 1
+ bgeu a2, a1, .L2
+.L1:
+ blez a2, .L2
+ slli a2, a2, 1
+ slli a3, a3, 1
+ bgtu a1, a2, .L1
+.L2:
+ li a0, 0
+.L3:
+ bltu a1, a2, .L4
+ sub a1, a1, a2
+ or a0, a0, a3
+.L4:
+ srli a3, a3, 1
+ srli a2, a2, 1
+ bnez a3, .L3
+.L5:
+ ret
--
2.13.0
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