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Message-ID: <87tu26w6gn.fsf@all.your.base.are.belong.to.us>
Date: Thu, 08 Dec 2022 11:11:20 +0100
From: Björn Töpel <bjorn@...nel.org>
To: guoren@...nel.org, arnd@...db.de, guoren@...nel.org,
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, palmer@...belt.com,
paul.walmsley@...ive.com, mark.rutland@....com,
zouyipeng@...wei.com, bigeasy@...utronix.de,
David.Laight@...lab.com, chenzhongjin@...wei.com,
greentime.hu@...ive.com, andy.chiu@...ive.com, ben@...adent.org.uk
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-riscv@...ts.infradead.org, Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH -next V10 04/10] riscv: entry: Convert to generic entry
guoren@...nel.org writes:
The RISC-V entry.S is much more paletable after this patch! :-)
Some minor things...
> 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 than before:
s/changes than before/changes/
> - More clear entry.S with handle_exception and ret_from_exception
> - Get rid of complex custom signal implementation
> - More readable syscall procedure
Maybe reword this a bit? It's a move from assembly to C (which, is much
more readable!).
> - Little modification on ret_from_fork & ret_from_kernel_thread
What changes?
> - 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>
> 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>
> ---
> arch/riscv/Kconfig | 1 +
> arch/riscv/include/asm/csr.h | 1 -
> arch/riscv/include/asm/entry-common.h | 8 +
> arch/riscv/include/asm/ptrace.h | 10 +-
> arch/riscv/include/asm/stacktrace.h | 5 +
> arch/riscv/include/asm/syscall.h | 6 +
> arch/riscv/include/asm/thread_info.h | 13 +-
> arch/riscv/kernel/entry.S | 237 ++++----------------------
> arch/riscv/kernel/irq.c | 15 ++
> arch/riscv/kernel/ptrace.c | 43 -----
> arch/riscv/kernel/signal.c | 21 +--
> arch/riscv/kernel/sys_riscv.c | 29 ++++
> arch/riscv/kernel/traps.c | 70 ++++++--
> arch/riscv/mm/fault.c | 16 +-
> 14 files changed, 175 insertions(+), 300 deletions(-)
> create mode 100644 arch/riscv/include/asm/entry-common.h
[...]
> diff --git a/arch/riscv/kernel/entry.S b/arch/riscv/kernel/entry.S
> index da44fe2d0d82..69097dfffdc9 100644
> --- a/arch/riscv/kernel/entry.S
> +++ b/arch/riscv/kernel/entry.S
> @@ -14,10 +14,6 @@
> #include <asm/asm-offsets.h>
> #include <asm/errata_list.h>
>
> -#if !IS_ENABLED(CONFIG_PREEMPTION)
> -.set resume_kernel, restore_all
> -#endif
> -
> ENTRY(handle_exception)
> /*
> * If coming from userspace, preserve the user thread pointer and load
> @@ -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
Not for this series, but at some point it would be nice to get rid of
the "move" pseudoinsn in favor of "mv".
[...]
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index f7fa973558bc..ee9a0ef672e9 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -17,6 +17,7 @@
> #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>
> @@ -99,10 +100,19 @@ 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 irq_state = irqentry_nmi_enter(regs); \
> + do_trap_error(regs, signo, code, regs->epc, "Oops - " str); \
> + irqentry_nmi_exit(regs, irq_state); \
> + } \
> + BUG_ON(!irqs_disabled()); \
> }
>
> DO_ERROR_INFO(do_trap_unknown,
> @@ -126,18 +136,38 @@ int handle_misaligned_store(struct pt_regs *regs);
>
> asmlinkage void __trap_section 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 irq_state = irqentry_nmi_enter(regs);
Please add a newline.
> + if (handle_misaligned_load(regs))
> + do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
> + "Oops - load address misaligned");
> + irqentry_nmi_exit(regs, irq_state);
> + }
> + BUG_ON(!irqs_disabled());
> }
>
> asmlinkage void __trap_section 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))
> + do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
> + "Oops - store (or AMO) address misaligned");
> + irqentry_exit_to_user_mode(regs);
> + } else {
> + irqentry_state_t irq_state = irqentry_nmi_enter(regs);
Please add a newline.
> + if (handle_misaligned_store(regs))
> + do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
> + "Oops - store (or AMO) address misaligned");
> + irqentry_nmi_exit(regs, irq_state);
> + }
> + BUG_ON(!irqs_disabled());
> }
> #endif
> DO_ERROR_INFO(do_trap_store_fault,
> @@ -159,7 +189,7 @@ static inline unsigned long get_break_insn_length(unsigned long pc)
> return GET_INSN_LENGTH(insn);
> }
>
> -asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
> +static void __do_trap_break(struct pt_regs *regs)
> {
> #ifdef CONFIG_KPROBES
> if (kprobe_single_step_handler(regs))
> @@ -189,6 +219,20 @@ asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
> else
> die(regs, "Kernel BUG");
> }
> +
> +asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
> +{
> + if (user_mode(regs)) {
> + irqentry_enter_from_user_mode(regs);
> + __do_trap_break(regs);
> + irqentry_exit_to_user_mode(regs);
> + } else {
> + irqentry_state_t irq_state = irqentry_nmi_enter(regs);
Please add a newline.
Björn
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