riscv: entry: Convert to generic entry

This patch converts riscv to use the generic entry infrastructure from
kernel/entry/*. The generic entry makes maintainers' work easier and
codes more elegant. Here are the changes:

 - More clear entry.S with handle_exception and ret_from_exception
 - Get rid of complex custom signal implementation
 - Move syscall procedure from assembly to C, which is much more
   readable.
 - Connect ret_from_fork & ret_from_kernel_thread to generic entry.
 - Wrap with irqentry_enter/exit and syscall_enter/exit_from_user_mode
 - Use the standard preemption code instead of custom

Suggested-by: Huacai Chen <chenhuacai@kernel.org>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>
Tested-by: Yipeng Zou <zouyipeng@huawei.com>
Tested-by: Jisheng Zhang <jszhang@kernel.org>
Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Link: https://lore.kernel.org/r/20230222033021.983168-5-guoren@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

7 files changed, 48 insertions, 15 deletions

diff --git a/arch/riscv/include/asm/asm-prototypes.h b/arch/riscv/include/asm/asm-prototypes.h
index ef386fcf3939..61ba8ed43d8f 100644
--- a/arch/riscv/include/asm/asm-prototypes.h
+++ b/arch/riscv/include/asm/asm-prototypes.h
@@ -27,5 +27,7 @@ DECLARE_DO_ERROR_INFO(do_trap_break);
 
 asmlinkage unsigned long get_overflow_stack(void);
 asmlinkage void handle_bad_stack(struct pt_regs *regs);
+asmlinkage void do_page_fault(struct pt_regs *regs);
+asmlinkage void do_irq(struct pt_regs *regs);
 
 #endif /* _ASM_RISCV_PROTOTYPES_H */
diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
index 0e571f6483d9..7c2b8cdb7b77 100644
--- a/arch/riscv/include/asm/csr.h
+++ b/arch/riscv/include/asm/csr.h
@@ -40,7 +40,6 @@
 #define SR_UXL		_AC(0x300000000, UL) /* XLEN mask for U-mode */
 #define SR_UXL_32	_AC(0x100000000, UL) /* XLEN = 32 for U-mode */
 #define SR_UXL_64	_AC(0x200000000, UL) /* XLEN = 64 for U-mode */
-#define SR_UXL_SHIFT	32
 #endif
 
 /* SATP flags */
diff --git a/arch/riscv/include/asm/entry-common.h b/arch/riscv/include/asm/entry-common.h
new file mode 100644
index 000000000000..6e4dee49d84b
--- /dev/null
+++ b/arch/riscv/include/asm/entry-common.h
@@ -0,0 +1,11 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _ASM_RISCV_ENTRY_COMMON_H
+#define _ASM_RISCV_ENTRY_COMMON_H
+
+#include <asm/stacktrace.h>
+
+void handle_page_fault(struct pt_regs *regs);
+void handle_break(struct pt_regs *regs);
+
+#endif /* _ASM_RISCV_ENTRY_COMMON_H */
diff --git a/arch/riscv/include/asm/ptrace.h b/arch/riscv/include/asm/ptrace.h
index 6ecd461129d2..b5b0adcc85c1 100644
--- a/arch/riscv/include/asm/ptrace.h
+++ b/arch/riscv/include/asm/ptrace.h
@@ -53,6 +53,9 @@ struct pt_regs {
 	unsigned long orig_a0;
 };
 
+#define PTRACE_SYSEMU			0x1f
+#define PTRACE_SYSEMU_SINGLESTEP	0x20
+
 #ifdef CONFIG_64BIT
 #define REG_FMT "%016lx"
 #else
@@ -121,8 +124,6 @@ extern unsigned long regs_get_kernel_stack_nth(struct pt_regs *regs,
 
 void prepare_ftrace_return(unsigned long *parent, unsigned long self_addr,
 			   unsigned long frame_pointer);
-int do_syscall_trace_enter(struct pt_regs *regs);
-void do_syscall_trace_exit(struct pt_regs *regs);
 
 /**
  * regs_get_register() - get register value from its offset
@@ -172,6 +173,11 @@ static inline unsigned long regs_get_kernel_argument(struct pt_regs *regs,
 	return 0;
 }
 
+static inline int regs_irqs_disabled(struct pt_regs *regs)
+{
+	return !(regs->status & SR_PIE);
+}
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_RISCV_PTRACE_H */
diff --git a/arch/riscv/include/asm/stacktrace.h b/arch/riscv/include/asm/stacktrace.h
index 3450c1912afd..f7e8ef2418b9 100644
--- a/arch/riscv/include/asm/stacktrace.h
+++ b/arch/riscv/include/asm/stacktrace.h
@@ -16,4 +16,9 @@ extern void notrace walk_stackframe(struct task_struct *task, struct pt_regs *re
 extern void dump_backtrace(struct pt_regs *regs, struct task_struct *task,
 			   const char *loglvl);
 
+static inline bool on_thread_stack(void)
+{
+	return !(((unsigned long)(current->stack) ^ current_stack_pointer) & ~(THREAD_SIZE - 1));
+}
+
 #endif /* _ASM_RISCV_STACKTRACE_H */
diff --git a/arch/riscv/include/asm/syscall.h b/arch/riscv/include/asm/syscall.h
index 384a63b86420..736110e1fd78 100644
--- a/arch/riscv/include/asm/syscall.h
+++ b/arch/riscv/include/asm/syscall.h
@@ -74,5 +74,26 @@ static inline int syscall_get_arch(struct task_struct *task)
 #endif
 }
 
+typedef long (*syscall_t)(ulong, ulong, ulong, ulong, ulong, ulong, ulong);
+static inline void syscall_handler(struct pt_regs *regs, ulong syscall)
+{
+	syscall_t fn;
+
+#ifdef CONFIG_COMPAT
+	if ((regs->status & SR_UXL) == SR_UXL_32)
+		fn = compat_sys_call_table[syscall];
+	else
+#endif
+		fn = sys_call_table[syscall];
+
+	regs->a0 = fn(regs->orig_a0, regs->a1, regs->a2,
+		      regs->a3, regs->a4, regs->a5, regs->a6);
+}
+
+static inline bool arch_syscall_is_vdso_sigreturn(struct pt_regs *regs)
+{
+	return false;
+}
+
 asmlinkage long sys_riscv_flush_icache(uintptr_t, uintptr_t, uintptr_t);
 #endif	/* _ASM_RISCV_SYSCALL_H */
diff --git a/arch/riscv/include/asm/thread_info.h b/arch/riscv/include/asm/thread_info.h
index f704c8dd57e0..e0d202134b44 100644
--- a/arch/riscv/include/asm/thread_info.h
+++ b/arch/riscv/include/asm/thread_info.h
@@ -67,6 +67,7 @@ struct thread_info {
 	long			kernel_sp;	/* Kernel stack pointer */
 	long			user_sp;	/* User stack pointer */
 	int			cpu;
+	unsigned long		syscall_work;	/* SYSCALL_WORK_ flags */
 };
 
 /*
@@ -89,26 +90,18 @@ struct thread_info {
  * - pending work-to-be-done flags are in lowest half-word
  * - other flags in upper half-word(s)
  */
-#define TIF_SYSCALL_TRACE	0	/* syscall trace active */
 #define TIF_NOTIFY_RESUME	1	/* callback before returning to user */
 #define TIF_SIGPENDING		2	/* signal pending */
 #define TIF_NEED_RESCHED	3	/* rescheduling necessary */
 #define TIF_RESTORE_SIGMASK	4	/* restore signal mask in do_signal() */
 #define TIF_MEMDIE		5	/* is terminating due to OOM killer */
-#define TIF_SYSCALL_TRACEPOINT  6       /* syscall tracepoint instrumentation */
-#define TIF_SYSCALL_AUDIT	7	/* syscall auditing */
-#define TIF_SECCOMP		8	/* syscall secure computing */
 #define TIF_NOTIFY_SIGNAL	9	/* signal notifications exist */
 #define TIF_UPROBE		10	/* uprobe breakpoint or singlestep */
 #define TIF_32BIT		11	/* compat-mode 32bit process */
 
-#define _TIF_SYSCALL_TRACE	(1 << TIF_SYSCALL_TRACE)
 #define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)
 #define _TIF_SIGPENDING		(1 << TIF_SIGPENDING)
 #define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)
-#define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
-#define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)
-#define _TIF_SECCOMP		(1 << TIF_SECCOMP)
 #define _TIF_NOTIFY_SIGNAL	(1 << TIF_NOTIFY_SIGNAL)
 #define _TIF_UPROBE		(1 << TIF_UPROBE)
 
@@ -116,8 +109,4 @@ struct thread_info {
 	(_TIF_NOTIFY_RESUME | _TIF_SIGPENDING | _TIF_NEED_RESCHED | \
 	 _TIF_NOTIFY_SIGNAL | _TIF_UPROBE)
 
-#define _TIF_SYSCALL_WORK \
-	(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_TRACEPOINT | _TIF_SYSCALL_AUDIT | \
-	 _TIF_SECCOMP)
-
 #endif /* _ASM_RISCV_THREAD_INFO_H */