Date:   Sun, 05 Feb 2023 11:43:44 +0100
From:   Conor Dooley <conor@...nel.org>
To:     guoren@...nel.org, arnd@...db.de, palmer@...osinc.com,
        tglx@...utronix.de, peterz@...radead.org, luto@...nel.org,
        conor.dooley@...rochip.com, heiko@...ech.de, jszhang@...nel.org,
        lazyparser@...il.com, falcon@...ylab.org, chenhuacai@...nel.org,
        apatel@...tanamicro.com, atishp@...shpatra.org,
        mark.rutland@....com, ben@...adent.org.uk, bjorn@...nel.org,
        miguel.ojeda.sandonis@...il.com
CC:     linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-riscv@...ts.infradead.org,
        Guo Ren <guoren@...ux.alibaba.com>,
        Björn Töpel <bjorn@...osinc.com>,
        Yipeng Zou <zouyipeng@...wei.com>
Subject: Re: [PATCH -next V16 4/7] riscv: entry: Convert to generic entry

Hey Guo Ren,

On 4 February 2023 08:02:10 GMT+01:00, guoren@...nel.org wrote:
>From: Guo Ren <guoren@...ux.alibaba.com>
>
>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@...nel.org>
>Reviewed-by: Björn Töpel <bjorn@...osinc.com>
>Tested-by: Yipeng Zou <zouyipeng@...wei.com>
>Tested-by: Jisheng Zhang <jszhang@...nel.org>
>Signed-off-by: Guo Ren <guoren@...ux.alibaba.com>
>Signed-off-by: Guo Ren <guoren@...nel.org>
>Cc: Ben Hutchings <ben@...adent.org.uk>
>---

Got some new errors added by this patch:
https://gist.github.com/conor-pwbot/3b300050a7a4a197bca809935584d809

Unfortunately I'm away from a computer at FOSDEM, so I haven't done any investigation
of the warnings.
Should be reproduceable with gcc-12 allmodconfig.

Thanks,
Conor.


> arch/riscv/Kconfig                      |   1 +
> arch/riscv/include/asm/asm-prototypes.h |   2 +
> arch/riscv/include/asm/csr.h            |   1 -
> arch/riscv/include/asm/entry-common.h   |  11 ++
> arch/riscv/include/asm/ptrace.h         |  10 +-
> arch/riscv/include/asm/stacktrace.h     |   5 +
> arch/riscv/include/asm/syscall.h        |  21 ++
> arch/riscv/include/asm/thread_info.h    |  13 +-
> arch/riscv/kernel/entry.S               | 242 ++++--------------------
> arch/riscv/kernel/head.h                |   1 -
> arch/riscv/kernel/ptrace.c              |  43 -----
> arch/riscv/kernel/signal.c              |  29 +--
> arch/riscv/kernel/traps.c               | 140 ++++++++++++--
> arch/riscv/mm/fault.c                   |   6 +-
> 14 files changed, 210 insertions(+), 315 deletions(-)
> create mode 100644 arch/riscv/include/asm/entry-common.h
>
>diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>index 7c814fbf9527..cbac7b4e3e06 100644
>--- a/arch/riscv/Kconfig
>+++ b/arch/riscv/Kconfig
>@@ -58,6 +58,7 @@ config RISCV
> 	select GENERIC_ATOMIC64 if !64BIT
> 	select GENERIC_CLOCKEVENTS_BROADCAST if SMP
> 	select GENERIC_EARLY_IOREMAP
>+	select GENERIC_ENTRY
> 	select GENERIC_GETTIMEOFDAY if HAVE_GENERIC_VDSO
> 	select GENERIC_IDLE_POLL_SETUP
> 	select GENERIC_IOREMAP if MMU
>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 67322f878e0d..7de4fb96f0b5 100644
>--- a/arch/riscv/include/asm/thread_info.h
>+++ b/arch/riscv/include/asm/thread_info.h
>@@ -66,6 +66,7 @@ struct thread_info {
> 	long			kernel_sp;	/* Kernel stack pointer */
> 	long			user_sp;	/* User stack pointer */
> 	int			cpu;
>+	unsigned long		syscall_work;	/* SYSCALL_WORK_ flags */
> };
> 
> /*
>@@ -88,26 +89,18 @@ 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)
> 
>@@ -115,8 +108,4 @@ 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 */
>diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
>index 99d38fdf8b18..bc322f92ba34 100644
>--- a/arch/riscv/kernel/entry.S
>+++ b/arch/riscv/kernel/entry.S
>@@ -14,11 +14,7 @@
> #include <asm/asm-offsets.h>
> #include <asm/errata_list.h>
> 
>-#if !IS_ENABLED(CONFIG_PREEMPTION)
>-.set resume_kernel, restore_all
>-#endif
>-
>-ENTRY(handle_exception)
>+SYM_CODE_START(handle_exception)
> 	/*
> 	 * If coming from userspace, preserve the user thread pointer and load
> 	 * the kernel thread pointer.  If we came from the kernel, the scratch
>@@ -106,19 +102,8 @@ _save_context:
> .option norelax
> 	la gp, __global_pointer$
> .option pop
>-
>-#ifdef CONFIG_TRACE_IRQFLAGS
>-	call __trace_hardirqs_off
>-#endif
>-
>-#ifdef CONFIG_CONTEXT_TRACKING_USER
>-	/* If previous state is in user mode, call user_exit_callable(). */
>-	li   a0, SR_PP
>-	and a0, s1, a0
>-	bnez a0, skip_context_tracking
>-	call user_exit_callable
>-skip_context_tracking:
>-#endif
>+	move a0, sp /* pt_regs */
>+	la ra, ret_from_exception
> 
> 	/*
> 	 * MSB of cause differentiates between
>@@ -126,38 +111,13 @@ skip_context_tracking:
> 	 */
> 	bge s4, zero, 1f
> 
>-	la ra, ret_from_exception
>-
> 	/* Handle interrupts */
>-	move a0, sp /* pt_regs */
>-	la a1, generic_handle_arch_irq
>-	jr a1
>-1:
>-	/*
>-	 * Exceptions run with interrupts enabled or disabled depending on the
>-	 * state of SR_PIE in m/sstatus.
>-	 */
>-	andi t0, s1, SR_PIE
>-	beqz t0, 1f
>-	/* kprobes, entered via ebreak, must have interrupts disabled. */
>-	li t0, EXC_BREAKPOINT
>-	beq s4, t0, 1f
>-#ifdef CONFIG_TRACE_IRQFLAGS
>-	call __trace_hardirqs_on
>-#endif
>-	csrs CSR_STATUS, SR_IE
>-
>+	tail do_irq
> 1:
>-	la ra, ret_from_exception
>-	/* Handle syscalls */
>-	li t0, EXC_SYSCALL
>-	beq s4, t0, handle_syscall
>-
> 	/* Handle other exceptions */
> 	slli t0, s4, RISCV_LGPTR
> 	la t1, excp_vect_table
> 	la t2, excp_vect_table_end
>-	move a0, sp /* pt_regs */
> 	add t0, t1, t0
> 	/* Check if exception code lies within bounds */
> 	bgeu t0, t2, 1f
>@@ -165,95 +125,17 @@ skip_context_tracking:
> 	jr t0
> 1:
> 	tail do_trap_unknown
>+SYM_CODE_END(handle_exception)
> 
>-handle_syscall:
>-#ifdef CONFIG_RISCV_M_MODE
>-	/*
>-	 * When running is M-Mode (no MMU config), MPIE does not get set.
>-	 * As a result, we need to force enable interrupts here because
>-	 * handle_exception did not do set SR_IE as it always sees SR_PIE
>-	 * being cleared.
>-	 */
>-	csrs CSR_STATUS, SR_IE
>-#endif
>-#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING_USER)
>-	/* Recover a0 - a7 for system calls */
>-	REG_L a0, PT_A0(sp)
>-	REG_L a1, PT_A1(sp)
>-	REG_L a2, PT_A2(sp)
>-	REG_L a3, PT_A3(sp)
>-	REG_L a4, PT_A4(sp)
>-	REG_L a5, PT_A5(sp)
>-	REG_L a6, PT_A6(sp)
>-	REG_L a7, PT_A7(sp)
>-#endif
>-	 /* save the initial A0 value (needed in signal handlers) */
>-	REG_S a0, PT_ORIG_A0(sp)
>-	/*
>-	 * Advance SEPC to avoid executing the original
>-	 * scall instruction on sret
>-	 */
>-	addi s2, s2, 0x4
>-	REG_S s2, PT_EPC(sp)
>-	/* Trace syscalls, but only if requested by the user. */
>-	REG_L t0, TASK_TI_FLAGS(tp)
>-	andi t0, t0, _TIF_SYSCALL_WORK
>-	bnez t0, handle_syscall_trace_enter
>-check_syscall_nr:
>-	/* Check to make sure we don't jump to a bogus syscall number. */
>-	li t0, __NR_syscalls
>-	la s0, sys_ni_syscall
>-	/*
>-	 * Syscall number held in a7.
>-	 * If syscall number is above allowed value, redirect to ni_syscall.
>-	 */
>-	bgeu a7, t0, 3f
>-#ifdef CONFIG_COMPAT
>-	REG_L s0, PT_STATUS(sp)
>-	srli s0, s0, SR_UXL_SHIFT
>-	andi s0, s0, (SR_UXL >> SR_UXL_SHIFT)
>-	li t0, (SR_UXL_32 >> SR_UXL_SHIFT)
>-	sub t0, s0, t0
>-	bnez t0, 1f
>-
>-	/* Call compat_syscall */
>-	la s0, compat_sys_call_table
>-	j 2f
>-1:
>-#endif
>-	/* Call syscall */
>-	la s0, sys_call_table
>-2:
>-	slli t0, a7, RISCV_LGPTR
>-	add s0, s0, t0
>-	REG_L s0, 0(s0)
>-3:
>-	jalr s0
>-
>-ret_from_syscall:
>-	/* Set user a0 to kernel a0 */
>-	REG_S a0, PT_A0(sp)
>-	/*
>-	 * We didn't execute the actual syscall.
>-	 * Seccomp already set return value for the current task pt_regs.
>-	 * (If it was configured with SECCOMP_RET_ERRNO/TRACE)
>-	 */
>-ret_from_syscall_rejected:
>-#ifdef CONFIG_DEBUG_RSEQ
>-	move a0, sp
>-	call rseq_syscall
>-#endif
>-	/* Trace syscalls, but only if requested by the user. */
>-	REG_L t0, TASK_TI_FLAGS(tp)
>-	andi t0, t0, _TIF_SYSCALL_WORK
>-	bnez t0, handle_syscall_trace_exit
>-
>+/*
>+ * The ret_from_exception must be called with interrupt disabled. Here is the
>+ * caller list:
>+ *  - handle_exception
>+ *  - ret_from_fork
>+ *  - ret_from_kernel_thread
>+ */
> SYM_CODE_START_NOALIGN(ret_from_exception)
> 	REG_L s0, PT_STATUS(sp)
>-	csrc CSR_STATUS, SR_IE
>-#ifdef CONFIG_TRACE_IRQFLAGS
>-	call __trace_hardirqs_off
>-#endif
> #ifdef CONFIG_RISCV_M_MODE
> 	/* the MPP value is too large to be used as an immediate arg for addi */
> 	li t0, SR_MPP
>@@ -261,17 +143,7 @@ SYM_CODE_START_NOALIGN(ret_from_exception)
> #else
> 	andi s0, s0, SR_SPP
> #endif
>-	bnez s0, resume_kernel
>-SYM_CODE_END(ret_from_exception)
>-
>-	/* Interrupts must be disabled here so flags are checked atomically */
>-	REG_L s0, TASK_TI_FLAGS(tp) /* current_thread_info->flags */
>-	andi s1, s0, _TIF_WORK_MASK
>-	bnez s1, resume_userspace_slow
>-resume_userspace:
>-#ifdef CONFIG_CONTEXT_TRACKING_USER
>-	call user_enter_callable
>-#endif
>+	bnez s0, 1f
> 
> 	/* Save unwound kernel stack pointer in thread_info */
> 	addi s0, sp, PT_SIZE_ON_STACK
>@@ -282,18 +154,7 @@ resume_userspace:
> 	 * structures again.
> 	 */
> 	csrw CSR_SCRATCH, tp
>-
>-restore_all:
>-#ifdef CONFIG_TRACE_IRQFLAGS
>-	REG_L s1, PT_STATUS(sp)
>-	andi t0, s1, SR_PIE
>-	beqz t0, 1f
>-	call __trace_hardirqs_on
>-	j 2f
> 1:
>-	call __trace_hardirqs_off
>-2:
>-#endif
> 	REG_L a0, PT_STATUS(sp)
> 	/*
> 	 * The current load reservation is effectively part of the processor's
>@@ -356,47 +217,10 @@ restore_all:
> #else
> 	sret
> #endif
>-
>-#if IS_ENABLED(CONFIG_PREEMPTION)
>-resume_kernel:
>-	REG_L s0, TASK_TI_PREEMPT_COUNT(tp)
>-	bnez s0, restore_all
>-	REG_L s0, TASK_TI_FLAGS(tp)
>-	andi s0, s0, _TIF_NEED_RESCHED
>-	beqz s0, restore_all
>-	call preempt_schedule_irq
>-	j restore_all
>-#endif
>-
>-resume_userspace_slow:
>-	/* Enter slow path for supplementary processing */
>-	move a0, sp /* pt_regs */
>-	move a1, s0 /* current_thread_info->flags */
>-	call do_work_pending
>-	j resume_userspace
>-
>-/* Slow paths for ptrace. */
>-handle_syscall_trace_enter:
>-	move a0, sp
>-	call do_syscall_trace_enter
>-	move t0, a0
>-	REG_L a0, PT_A0(sp)
>-	REG_L a1, PT_A1(sp)
>-	REG_L a2, PT_A2(sp)
>-	REG_L a3, PT_A3(sp)
>-	REG_L a4, PT_A4(sp)
>-	REG_L a5, PT_A5(sp)
>-	REG_L a6, PT_A6(sp)
>-	REG_L a7, PT_A7(sp)
>-	bnez t0, ret_from_syscall_rejected
>-	j check_syscall_nr
>-handle_syscall_trace_exit:
>-	move a0, sp
>-	call do_syscall_trace_exit
>-	j ret_from_exception
>+SYM_CODE_END(ret_from_exception)
> 
> #ifdef CONFIG_VMAP_STACK
>-handle_kernel_stack_overflow:
>+SYM_CODE_START_LOCAL(handle_kernel_stack_overflow)
> 	/*
> 	 * Takes the psuedo-spinlock for the shadow stack, in case multiple
> 	 * harts are concurrently overflowing their kernel stacks.  We could
>@@ -505,23 +329,25 @@ restore_caller_reg:
> 	REG_S s5, PT_TP(sp)
> 	move a0, sp
> 	tail handle_bad_stack
>+SYM_CODE_END(handle_kernel_stack_overflow)
> #endif
> 
>-END(handle_exception)
>-
>-ENTRY(ret_from_fork)
>+SYM_CODE_START(ret_from_fork)
>+	call schedule_tail
>+	move a0, sp /* pt_regs */
> 	la ra, ret_from_exception
>-	tail schedule_tail
>-ENDPROC(ret_from_fork)
>+	tail syscall_exit_to_user_mode
>+SYM_CODE_END(ret_from_fork)
> 
>-ENTRY(ret_from_kernel_thread)
>+SYM_CODE_START(ret_from_kernel_thread)
> 	call schedule_tail
> 	/* Call fn(arg) */
>-	la ra, ret_from_exception
> 	move a0, s1
>-	jr s0
>-ENDPROC(ret_from_kernel_thread)
>-
>+	jalr s0
>+	move a0, sp /* pt_regs */
>+	la ra, ret_from_exception
>+	tail syscall_exit_to_user_mode
>+SYM_CODE_END(ret_from_kernel_thread)
> 
> /*
>  * Integer register context switch
>@@ -533,7 +359,7 @@ ENDPROC(ret_from_kernel_thread)
>  * The value of a0 and a1 must be preserved by this function, as that's how
>  * arguments are passed to schedule_tail.
>  */
>-ENTRY(__switch_to)
>+SYM_FUNC_START(__switch_to)
> 	/* Save context into prev->thread */
> 	li    a4,  TASK_THREAD_RA
> 	add   a3, a0, a4
>@@ -570,7 +396,7 @@ ENTRY(__switch_to)
> 	/* The offset of thread_info in task_struct is zero. */
> 	move tp, a1
> 	ret
>-ENDPROC(__switch_to)
>+SYM_FUNC_END(__switch_to)
> 
> #ifndef CONFIG_MMU
> #define do_page_fault do_trap_unknown
>@@ -579,7 +405,7 @@ ENDPROC(__switch_to)
> 	.section ".rodata"
> 	.align LGREG
> 	/* Exception vector table */
>-ENTRY(excp_vect_table)
>+SYM_CODE_START(excp_vect_table)
> 	RISCV_PTR do_trap_insn_misaligned
> 	ALT_INSN_FAULT(RISCV_PTR do_trap_insn_fault)
> 	RISCV_PTR do_trap_insn_illegal
>@@ -588,7 +414,7 @@ ENTRY(excp_vect_table)
> 	RISCV_PTR do_trap_load_fault
> 	RISCV_PTR do_trap_store_misaligned
> 	RISCV_PTR do_trap_store_fault
>-	RISCV_PTR do_trap_ecall_u /* system call, gets intercepted */
>+	RISCV_PTR do_trap_ecall_u /* system call */
> 	RISCV_PTR do_trap_ecall_s
> 	RISCV_PTR do_trap_unknown
> 	RISCV_PTR do_trap_ecall_m
>@@ -598,11 +424,11 @@ ENTRY(excp_vect_table)
> 	RISCV_PTR do_trap_unknown
> 	RISCV_PTR do_page_fault   /* store page fault */
> excp_vect_table_end:
>-END(excp_vect_table)
>+SYM_CODE_END(excp_vect_table)
> 
> #ifndef CONFIG_MMU
>-ENTRY(__user_rt_sigreturn)
>+SYM_CODE_START(__user_rt_sigreturn)
> 	li a7, __NR_rt_sigreturn
> 	scall
>-END(__user_rt_sigreturn)
>+SYM_CODE_END(__user_rt_sigreturn)
> #endif
>diff --git a/arch/riscv/kernel/head.h b/arch/riscv/kernel/head.h
>index 726731ada534..a556fdaafed9 100644
>--- a/arch/riscv/kernel/head.h
>+++ b/arch/riscv/kernel/head.h
>@@ -10,7 +10,6 @@
> 
> extern atomic_t hart_lottery;
> 
>-asmlinkage void do_page_fault(struct pt_regs *regs);
> asmlinkage void __init setup_vm(uintptr_t dtb_pa);
> #ifdef CONFIG_XIP_KERNEL
> asmlinkage void __init __copy_data(void);
>diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
>index 44f4b1ca315d..23c48b14a0e7 100644
>--- a/arch/riscv/kernel/ptrace.c
>+++ b/arch/riscv/kernel/ptrace.c
>@@ -19,9 +19,6 @@
> #include <linux/sched.h>
> #include <linux/sched/task_stack.h>
> 
>-#define CREATE_TRACE_POINTS
>-#include <trace/events/syscalls.h>
>-
> enum riscv_regset {
> 	REGSET_X,
> #ifdef CONFIG_FPU
>@@ -228,46 +225,6 @@ long arch_ptrace(struct task_struct *child, long request,
> 	return ret;
> }
> 
>-/*
>- * Allows PTRACE_SYSCALL to work.  These are called from entry.S in
>- * {handle,ret_from}_syscall.
>- */
>-__visible int do_syscall_trace_enter(struct pt_regs *regs)
>-{
>-	if (test_thread_flag(TIF_SYSCALL_TRACE))
>-		if (ptrace_report_syscall_entry(regs))
>-			return -1;
>-
>-	/*
>-	 * Do the secure computing after ptrace; failures should be fast.
>-	 * If this fails we might have return value in a0 from seccomp
>-	 * (via SECCOMP_RET_ERRNO/TRACE).
>-	 */
>-	if (secure_computing() == -1)
>-		return -1;
>-
>-#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
>-	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
>-		trace_sys_enter(regs, syscall_get_nr(current, regs));
>-#endif
>-
>-	audit_syscall_entry(regs->a7, regs->a0, regs->a1, regs->a2, regs->a3);
>-	return 0;
>-}
>-
>-__visible void do_syscall_trace_exit(struct pt_regs *regs)
>-{
>-	audit_syscall_exit(regs);
>-
>-	if (test_thread_flag(TIF_SYSCALL_TRACE))
>-		ptrace_report_syscall_exit(regs, 0);
>-
>-#ifdef CONFIG_HAVE_SYSCALL_TRACEPOINTS
>-	if (test_thread_flag(TIF_SYSCALL_TRACEPOINT))
>-		trace_sys_exit(regs, regs_return_value(regs));
>-#endif
>-}
>-
> #ifdef CONFIG_COMPAT
> static int compat_riscv_gpr_get(struct task_struct *target,
> 				const struct user_regset *regset,
>diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
>index bfb2afa4135f..2e365084417e 100644
>--- a/arch/riscv/kernel/signal.c
>+++ b/arch/riscv/kernel/signal.c
>@@ -12,6 +12,7 @@
> #include <linux/syscalls.h>
> #include <linux/resume_user_mode.h>
> #include <linux/linkage.h>
>+#include <linux/entry-common.h>
> 
> #include <asm/ucontext.h>
> #include <asm/vdso.h>
>@@ -274,7 +275,7 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
> 	signal_setup_done(ret, ksig, 0);
> }
> 
>-static void do_signal(struct pt_regs *regs)
>+void arch_do_signal_or_restart(struct pt_regs *regs)
> {
> 	struct ksignal ksig;
> 
>@@ -311,29 +312,3 @@ static void do_signal(struct pt_regs *regs)
> 	 */
> 	restore_saved_sigmask();
> }
>-
>-/*
>- * Handle any pending work on the resume-to-userspace path, as indicated by
>- * _TIF_WORK_MASK. Entered from assembly with IRQs off.
>- */
>-asmlinkage __visible void do_work_pending(struct pt_regs *regs,
>-					  unsigned long thread_info_flags)
>-{
>-	do {
>-		if (thread_info_flags & _TIF_NEED_RESCHED) {
>-			schedule();
>-		} else {
>-			local_irq_enable();
>-			if (thread_info_flags & _TIF_UPROBE)
>-				uprobe_notify_resume(regs);
>-			/* Handle pending signal delivery */
>-			if (thread_info_flags & (_TIF_SIGPENDING |
>-						 _TIF_NOTIFY_SIGNAL))
>-				do_signal(regs);
>-			if (thread_info_flags & _TIF_NOTIFY_RESUME)
>-				resume_user_mode_work(regs);
>-		}
>-		local_irq_disable();
>-		thread_info_flags = read_thread_flags();
>-	} while (thread_info_flags & _TIF_WORK_MASK);
>-}
>diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
>index 96ec76c54ff2..69d619ddbcd5 100644
>--- a/arch/riscv/kernel/traps.c
>+++ b/arch/riscv/kernel/traps.c
>@@ -17,12 +17,14 @@
> #include <linux/module.h>
> #include <linux/irq.h>
> #include <linux/kexec.h>
>+#include <linux/entry-common.h>
> 
> #include <asm/asm-prototypes.h>
> #include <asm/bug.h>
> #include <asm/csr.h>
> #include <asm/processor.h>
> #include <asm/ptrace.h>
>+#include <asm/syscall.h>
> #include <asm/thread_info.h>
> 
> int show_unhandled_signals = 1;
>@@ -99,10 +101,18 @@ static void do_trap_error(struct pt_regs *regs, int signo, int code,
> #else
> #define __trap_section noinstr
> #endif
>-#define DO_ERROR_INFO(name, signo, code, str)				\
>-asmlinkage __visible __trap_section void name(struct pt_regs *regs)	\
>-{									\
>-	do_trap_error(regs, signo, code, regs->epc, "Oops - " str);	\
>+#define DO_ERROR_INFO(name, signo, code, str)					\
>+asmlinkage __visible __trap_section void name(struct pt_regs *regs)		\
>+{										\
>+	if (user_mode(regs)) {							\
>+		irqentry_enter_from_user_mode(regs);				\
>+		do_trap_error(regs, signo, code, regs->epc, "Oops - " str);	\
>+		irqentry_exit_to_user_mode(regs);				\
>+	} else {								\
>+		irqentry_state_t state = irqentry_nmi_enter(regs);		\
>+		do_trap_error(regs, signo, code, regs->epc, "Oops - " str);	\
>+		irqentry_nmi_exit(regs, state);					\
>+	}									\
> }
> 
> DO_ERROR_INFO(do_trap_unknown,
>@@ -124,26 +134,50 @@ DO_ERROR_INFO(do_trap_store_misaligned,
> int handle_misaligned_load(struct pt_regs *regs);
> int handle_misaligned_store(struct pt_regs *regs);
> 
>-asmlinkage void __trap_section do_trap_load_misaligned(struct pt_regs *regs)
>+asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs *regs)
> {
>-	if (!handle_misaligned_load(regs))
>-		return;
>-	do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
>-		      "Oops - load address misaligned");
>+	if (user_mode(regs)) {
>+		irqentry_enter_from_user_mode(regs);
>+
>+		if (handle_misaligned_load(regs))
>+			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
>+			      "Oops - load address misaligned");
>+
>+		irqentry_exit_to_user_mode(regs);
>+	} else {
>+		irqentry_state_t state = irqentry_nmi_enter(regs);
>+
>+		if (handle_misaligned_load(regs))
>+			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
>+			      "Oops - load address misaligned");
>+
>+		irqentry_nmi_exit(regs, state);
>+	}
> }
> 
>-asmlinkage void __trap_section do_trap_store_misaligned(struct pt_regs *regs)
>+asmlinkage __visible __trap_section void do_trap_store_misaligned(struct pt_regs *regs)
> {
>-	if (!handle_misaligned_store(regs))
>-		return;
>-	do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
>-		      "Oops - store (or AMO) address misaligned");
>+	if (user_mode(regs)) {
>+		irqentry_enter_from_user_mode(regs);
>+
>+		if (handle_misaligned_store(regs))
>+	

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