Re: [PATCH V3 14/22] LoongArch: Add signal handling support
From: Huacai Chen <hidden>
Date: 2021-09-18 07:13:07
Also in:
linux-arch, lkml
Hi, Eric, On Sat, Sep 18, 2021 at 5:10 AM Eric W. Biederman [off-list ref] wrote:
Huacai Chen [off-list ref] writes:quoted
This patch adds signal handling support for LoongArch.My overall impression is that it looks like this code has a lot of boilerplate code copied from mips that mips needs because of it's long history, but that a fresh architecture should not need. For example does LoongArch have a version without built in floating point support?
Some of these structures seems need rethinking, But we really have LoongArch-based MCUs now (no FP, no SMP, and even no MMU).
To the best of my knowledge it has been decades since anyone built a cpu capable of running Linux that doesn't have built in floating point support. Similarly this includes code for parameterize some of the userspace ABI. Since you only have a single userspace ABI there should not need to be any parameters. So removing the unnecessary parameters should simplify the code. I have a few more comments inline along the same lines. Ericquoted
Signed-off-by: Huacai Chen <redacted> --- arch/loongarch/include/asm/abi.h | 27 ++ arch/loongarch/include/uapi/asm/sigcontext.h | 40 ++ arch/loongarch/include/uapi/asm/ucontext.h | 35 ++ arch/loongarch/kernel/signal-common.h | 38 ++ arch/loongarch/kernel/signal.c | 467 +++++++++++++++++++ 5 files changed, 607 insertions(+) create mode 100644 arch/loongarch/include/asm/abi.h create mode 100644 arch/loongarch/include/uapi/asm/sigcontext.h create mode 100644 arch/loongarch/include/uapi/asm/ucontext.h create mode 100644 arch/loongarch/kernel/signal-common.h create mode 100644 arch/loongarch/kernel/signal.cdiff --git a/arch/loongarch/include/asm/abi.h b/arch/loongarch/include/asm/abi.h new file mode 100644 index 000000000000..ced8534db4df --- /dev/null +++ b/arch/loongarch/include/asm/abi.h@@ -0,0 +1,27 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * Copyright (C) 2020-2021 Loongson Technology Corporation Limited + */ +#ifndef _ASM_ABI_H +#define _ASM_ABI_H + +#include <linux/signal_types.h> + +#include <asm/signal.h> +#include <asm/siginfo.h> +#include <asm/vdso.h> + +struct loongarch_abi { + const unsigned long restart; + const int audit_arch; + + unsigned int off_sc_fpregs; + unsigned int off_sc_fcc; + unsigned int off_sc_fcsr; + unsigned int off_sc_vcsr; + unsigned int off_sc_flags; + + struct loongarch_vdso_info *vdso; +};This header file is confusing. It says ABI but it isn't under the uapi tree. On mips with decades of history and a nabi, oabi, etc, the similar header file which includes function pointers makes a smidgen of sense. Since you aren't mips and your architecture is new you should be able to have a single userspace ABI and hard code everything. At least to get started with. That should make for simpler code as well.quoted
+ +#endif /* _ASM_ABI_H */diff --git a/arch/loongarch/include/uapi/asm/sigcontext.h b/arch/loongarch/include/uapi/asm/sigcontext.h new file mode 100644 index 000000000000..da0e5bac2d80 --- /dev/null +++ b/arch/loongarch/include/uapi/asm/sigcontext.h@@ -0,0 +1,40 @@ +/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */ +/* + * Author: Hanlu Li <lihanlu@loongson.cn> + * Huacai Chen <chenhuacai@loongson.cn> + * + * Copyright (C) 2020-2021 Loongson Technology Corporation Limited + */ +#ifndef _UAPI_ASM_SIGCONTEXT_H +#define _UAPI_ASM_SIGCONTEXT_H + +#include <linux/types.h> +#include <asm/processor.h> + +/* scalar FP context was used */ +#define USED_FP (1 << 0) + +/* extended context was used, see struct extcontext for details */ +#define USED_EXTCONTEXT (1 << 1) + +#include <linux/posix_types.h> +/* + * Keep this struct definition in sync with the sigcontext fragment + * in arch/loongarch/kernel/asm-offsets.cIf this is uapi this can't change (except for consuming the reserved fields). Making this comment misleading.quoted
+ * + */ +struct sigcontext { + __u64 sc_pc; + __u64 sc_regs[32]; + __u32 sc_flags; + + __u32 sc_fcsr; + __u32 sc_vcsr;You might want to document the 32bit hole in your structure here.quoted
+ __u64 sc_fcc; + __u64 sc_scr[4]; + + union fpureg sc_fpregs[32] FPU_ALIGN; + __u8 sc_reserved[4096] __attribute__((__aligned__(16))); +}; + +#endif /* _UAPI_ASM_SIGCONTEXT_H */diff --git a/arch/loongarch/include/uapi/asm/ucontext.h b/arch/loongarch/include/uapi/asm/ucontext.h new file mode 100644 index 000000000000..12577e22b1c7 --- /dev/null +++ b/arch/loongarch/include/uapi/asm/ucontext.h@@ -0,0 +1,35 @@ +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */ +#ifndef __LOONGARCH_UAPI_ASM_UCONTEXT_H +#define __LOONGARCH_UAPI_ASM_UCONTEXT_H + +/** + * struct ucontext - user context structure + * @uc_flags: + * @uc_link: + * @uc_stack: + * @uc_mcontext: holds basic processor state + * @uc_sigmask: + * @uc_extcontext: holds extended processor state + */ +struct ucontext { + unsigned long uc_flags; + struct ucontext *uc_link; + stack_t uc_stack; + sigset_t uc_sigmask; + /* There's some padding here to allow sigset_t to be expanded in the + * future. Though this is unlikely, other architectures put uc_sigmask + * at the end of this structure and explicitly state it can be + * expanded, so we didn't want to box ourselves in here. */ + __u8 __unused[1024 / 8 - sizeof(sigset_t)]; + /* We can't put uc_sigmask at the end of this structure because we need + * to be able to expand sigcontext in the future. For example, the + * vector ISA extension will almost certainly add ISA state. We want + * to ensure all user-visible ISA state can be saved and restored via a + * ucontext, so we're putting this at the end in order to allow for + * infinite extensibility. Since we know this will be extended and we + * assume sigset_t won't be extended an extreme amount, we're + * prioritizing this. */ + struct sigcontext uc_mcontext; +}; + +#endif /* __LOONGARCH_UAPI_ASM_UCONTEXT_H */diff --git a/arch/loongarch/kernel/signal-common.h b/arch/loongarch/kernel/signal-common.h new file mode 100644 index 000000000000..1693fbdedeaa --- /dev/null +++ b/arch/loongarch/kernel/signal-common.h@@ -0,0 +1,38 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +/* + * Author: Hanlu Li <lihanlu@loongson.cn> + * Huacai Chen <chenhuacai@loongson.cn> + * + * Copyright (C) 2020-2021 Loongson Technology Corporation Limited + */ + +#ifndef __SIGNAL_COMMON_H +#define __SIGNAL_COMMON_H + +/* #define DEBUG_SIG */ + +#ifdef DEBUG_SIG +# define DEBUGP(fmt, args...) printk("%s: " fmt, __func__, ##args) +#else +# define DEBUGP(fmt, args...) +#endifThis is only used once in arch/loongarch/kernel/signal.c so you probably want to keep this define local to that file.
OK, thanks. Huacai
quoted
+/* + * Determine which stack to use.. + */ +extern void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs, + size_t frame_size); +/* Check and clear pending FPU exceptions in saved CSR */ +extern int fpcsr_pending(unsigned int __user *fpcsr); + +/* Make sure we will not lose FPU ownership */ +#define lock_fpu_owner() ({ preempt_disable(); pagefault_disable(); }) +#define unlock_fpu_owner() ({ pagefault_enable(); preempt_enable(); }) + +/* Assembly functions to move context to/from the FPU */ +extern asmlinkage int +_save_fp_context(void __user *fpregs, void __user *fcc, void __user *csr); +extern asmlinkage int +_restore_fp_context(void __user *fpregs, void __user *fcc, void __user *csr); + +#endif /* __SIGNAL_COMMON_H */diff --git a/arch/loongarch/kernel/signal.c b/arch/loongarch/kernel/signal.c new file mode 100644 index 000000000000..78319d2575c6 --- /dev/null +++ b/arch/loongarch/kernel/signal.c@@ -0,0 +1,467 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Author: Hanlu Li <lihanlu@loongson.cn> + * Huacai Chen <chenhuacai@loongson.cn> + * Copyright (C) 2020-2021 Loongson Technology Corporation Limited + * + * Derived from MIPS: + * Copyright (C) 1991, 1992 Linus Torvalds + * Copyright (C) 1994 - 2000 Ralf Baechle + * Copyright (C) 1999, 2000 Silicon Graphics, Inc. + * Copyright (C) 2014, Imagination Technologies Ltd. + */ +#include <linux/audit.h> +#include <linux/cache.h> +#include <linux/context_tracking.h> +#include <linux/irqflags.h> +#include <linux/sched.h> +#include <linux/mm.h> +#include <linux/personality.h> +#include <linux/smp.h> +#include <linux/kernel.h> +#include <linux/signal.h> +#include <linux/errno.h> +#include <linux/wait.h> +#include <linux/ptrace.h> +#include <linux/unistd.h> +#include <linux/uprobes.h> +#include <linux/compiler.h> +#include <linux/syscalls.h> +#include <linux/uaccess.h> +#include <linux/tracehook.h> + +#include <asm/abi.h> +#include <asm/asm.h> +#include <asm/cacheflush.h> +#include <asm/fpu.h> +#include <asm/ucontext.h> +#include <asm/cpu-features.h> + +#include "signal-common.h" + +static int (*save_fp_context)(void __user *sc); +static int (*restore_fp_context)(void __user *sc); + +struct rt_sigframe { + struct siginfo rs_info; + struct ucontext rs_uctx; +}; + +/* + * Thread saved context copy to/from a signal context presumed to be on the + * user stack, and therefore accessed with appropriate macros from uaccess.h. + */ +static int copy_fp_to_sigcontext(void __user *sc) +{ + struct loongarch_abi *abi = current->thread.abi; + uint64_t __user *fpregs = sc + abi->off_sc_fpregs; + uint64_t __user *fcc = sc + abi->off_sc_fcc; + uint32_t __user *csr = sc + abi->off_sc_fcsr; + int i; + int err = 0; + int inc = 1; + + for (i = 0; i < NUM_FPU_REGS; i += inc) { + err |= + __put_user(get_fpr64(¤t->thread.fpu.fpr[i], 0), + &fpregs[4*i]); + } + err |= __put_user(current->thread.fpu.fcsr, csr); + err |= __put_user(current->thread.fpu.fcc, fcc); + + return err; +} + +static int copy_fp_from_sigcontext(void __user *sc) +{ + struct loongarch_abi *abi = current->thread.abi; + uint64_t __user *fpregs = sc + abi->off_sc_fpregs; + uint64_t __user *fcc = sc + abi->off_sc_fcc; + uint32_t __user *csr = sc + abi->off_sc_fcsr; + int i; + int err = 0; + int inc = 1; + u64 fpr_val; + + for (i = 0; i < NUM_FPU_REGS; i += inc) { + err |= __get_user(fpr_val, &fpregs[4*i]); + set_fpr64(¤t->thread.fpu.fpr[i], 0, fpr_val); + } + err |= __get_user(current->thread.fpu.fcsr, csr); + err |= __get_user(current->thread.fpu.fcc, fcc); + + return err; +} + +/* + * Wrappers for the assembly _{save,restore}_fp_context functions. + */ +static int save_hw_fp_context(void __user *sc) +{ + struct loongarch_abi *abi = current->thread.abi; + uint64_t __user *fpregs = sc + abi->off_sc_fpregs; + uint64_t __user *fcc = sc + abi->off_sc_fcc; + uint32_t __user *fcsr = sc + abi->off_sc_fcsr; + + return _save_fp_context(fpregs, fcc, fcsr); +} + +static int restore_hw_fp_context(void __user *sc) +{ + struct loongarch_abi *abi = current->thread.abi; + uint64_t __user *fpregs = sc + abi->off_sc_fpregs; + uint64_t __user *fcc = sc + abi->off_sc_fcc; + uint32_t __user *csr = sc + abi->off_sc_fcsr; + + return _restore_fp_context(fpregs, fcc, csr); +} + +/* + * Helper routines + */ +static int protected_save_fp_context(void __user *sc) +{ + int err = 0; + unsigned int used; + struct loongarch_abi *abi = current->thread.abi; + uint64_t __user *fpregs = sc + abi->off_sc_fpregs; + uint32_t __user *fcc = sc + abi->off_sc_fcsr; + uint32_t __user *fcsr = sc + abi->off_sc_fcsr; + uint32_t __user *vcsr = sc + abi->off_sc_vcsr; + uint32_t __user *flags = sc + abi->off_sc_flags; + + used = used_math() ? USED_FP : 0; + if (!used) + goto fp_done; + + while (1) { + lock_fpu_owner(); + if (is_fpu_owner()) + err = save_fp_context(sc); + else + err |= copy_fp_to_sigcontext(sc); + unlock_fpu_owner(); + if (likely(!err)) + break; + /* touch the sigcontext and try again */ + err = __put_user(0, &fpregs[0]) | + __put_user(0, &fpregs[32*4 - 1]) | + __put_user(0, fcc) | + __put_user(0, fcsr) | + __put_user(0, vcsr); + if (err) + return err; /* really bad sigcontext */ + } + +fp_done: + return __put_user(used, flags); +} + +static int protected_restore_fp_context(void __user *sc) +{ + unsigned int used; + int err = 0, sig = 0, tmp __maybe_unused; + struct loongarch_abi *abi = current->thread.abi; + uint64_t __user *fpregs = sc + abi->off_sc_fpregs; + uint32_t __user *fcsr = sc + abi->off_sc_fcsr; + uint32_t __user *fcc = sc + abi->off_sc_fcsr; + uint32_t __user *vcsr = sc + abi->off_sc_vcsr; + uint32_t __user *flags = sc + abi->off_sc_flags; + + err = __get_user(used, flags); + conditional_used_math(used & USED_FP); + + /* + * The signal handler may have used FPU; give it up if the program + * doesn't want it following sigreturn. + */ + if (err || !(used & USED_FP)) + lose_fpu(0); + + if (err) + return err; + + if (!(used & USED_FP)) + goto fp_done; + + err = sig = fpcsr_pending(fcsr); + if (err < 0) + return err; + + while (1) { + lock_fpu_owner(); + if (is_fpu_owner()) + err = restore_fp_context(sc); + else + err |= copy_fp_from_sigcontext(sc); + unlock_fpu_owner(); + if (likely(!err)) + break; + /* touch the sigcontext and try again */ + err = __get_user(tmp, &fpregs[0]) | + __get_user(tmp, &fpregs[32*4 - 1]) | + __get_user(tmp, fcc) | + __get_user(tmp, fcsr) | + __get_user(tmp, vcsr); + if (err) + break; /* really bad sigcontext */ + } + +fp_done: + return err ?: sig; +} + +static int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc) +{ + int err = 0; + int i; + + err |= __put_user(regs->csr_epc, &sc->sc_pc); + + err |= __put_user(0, &sc->sc_regs[0]); + for (i = 1; i < 32; i++) + err |= __put_user(regs->regs[i], &sc->sc_regs[i]); + + /* + * Save FPU state to signal context. Signal handler + * will "inherit" current FPU state. + */ + err |= protected_save_fp_context(sc); + + return err; +} + +int fpcsr_pending(unsigned int __user *fpcsr) +{ + int err, sig = 0; + unsigned int csr, enabled; + + err = __get_user(csr, fpcsr); + enabled = ((csr & FPU_CSR_ALL_E) << 24); + /* + * If the signal handler set some FPU exceptions, clear it and + * send SIGFPE. + */ + if (csr & enabled) { + csr &= ~enabled; + err |= __put_user(csr, fpcsr); + sig = SIGFPE; + } + return err ?: sig; +} + +static int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc) +{ + int err = 0; + int i; + + /* Always make any pending restarted system calls return -EINTR */ + current->restart_block.fn = do_no_restart_syscall; + + err |= __get_user(regs->csr_epc, &sc->sc_pc); + + for (i = 1; i < 32; i++) + err |= __get_user(regs->regs[i], &sc->sc_regs[i]); + + return err ?: protected_restore_fp_context(sc); +} + +void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs, + size_t frame_size) +{ + unsigned long sp; + + /* Default to using normal stack */ + sp = regs->regs[3]; + sp -= 32; /* Reserve 32-bytes. */ + + sp = sigsp(sp, ksig); + + return (void __user *)((sp - frame_size) & ALMASK); +} + +/* + * Atomically swap in the new signal mask, and wait for a signal. + */ + +asmlinkage long sys_rt_sigreturn(void) +{ + struct rt_sigframe __user *frame; + struct pt_regs *regs; + sigset_t set; + int sig; + + regs = current_pt_regs(); + frame = (struct rt_sigframe __user *)regs->regs[3]; + if (!access_ok(frame, sizeof(*frame))) + goto badframe; + if (__copy_from_user(&set, &frame->rs_uctx.uc_sigmask, sizeof(set))) + goto badframe; + + set_current_blocked(&set); + + sig = restore_sigcontext(regs, &frame->rs_uctx.uc_mcontext); + if (sig < 0) + goto badframe; + else if (sig) + force_sig(sig); + + if (restore_altstack(&frame->rs_uctx.uc_stack)) + goto badframe; + + return regs->regs[4]; + +badframe: + force_sig(SIGSEGV); + return 0; +} + +static int setup_rt_frame(void *sig_return, struct ksignal *ksig, + struct pt_regs *regs, sigset_t *set) +{ + struct rt_sigframe __user *frame; + int err = 0; + + frame = get_sigframe(ksig, regs, sizeof(*frame)); + if (!access_ok(frame, sizeof(*frame))) + return -EFAULT; + + /* Create siginfo. */ + err |= copy_siginfo_to_user(&frame->rs_info, &ksig->info); + + /* Create the ucontext. */ + err |= __put_user(0, &frame->rs_uctx.uc_flags); + err |= __put_user(NULL, &frame->rs_uctx.uc_link); + err |= __save_altstack(&frame->rs_uctx.uc_stack, regs->regs[3]); + err |= setup_sigcontext(regs, &frame->rs_uctx.uc_mcontext); + err |= __copy_to_user(&frame->rs_uctx.uc_sigmask, set, sizeof(*set)); + + if (err) + return -EFAULT; + + /* + * Arguments to signal handler: + * + * a0 = signal number + * a1 = 0 (should be cause) + * a2 = pointer to ucontext + * + * $25 and c0_epc point to the signal handler, $29 points to + * the struct rt_sigframe. + */ + regs->regs[4] = ksig->sig; + regs->regs[5] = (unsigned long) &frame->rs_info; + regs->regs[6] = (unsigned long) &frame->rs_uctx; + regs->regs[3] = (unsigned long) frame; + regs->regs[1] = (unsigned long) sig_return; + regs->csr_epc = (unsigned long) ksig->ka.sa.sa_handler; + + DEBUGP("SIG deliver (%s:%d): sp=0x%p pc=0x%lx ra=0x%lx\n", + current->comm, current->pid, + frame, regs->csr_epc, regs->regs[1]); + + return 0; +} + +struct loongarch_abi loongarch_abi = { + .restart = __NR_restart_syscall, +#ifdef CONFIG_32BIT + .audit_arch = AUDIT_ARCH_LOONGARCH32, +#else + .audit_arch = AUDIT_ARCH_LOONGARCH64, +#endif + + .off_sc_fpregs = offsetof(struct sigcontext, sc_fpregs), + .off_sc_fcc = offsetof(struct sigcontext, sc_fcc), + .off_sc_fcsr = offsetof(struct sigcontext, sc_fcsr), + .off_sc_vcsr = offsetof(struct sigcontext, sc_vcsr), + .off_sc_flags = offsetof(struct sigcontext, sc_flags), + + .vdso = &vdso_info, +}; + +static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) +{ + int ret; + sigset_t *oldset = sigmask_to_save(); + struct loongarch_abi *abi = current->thread.abi; + void *vdso = current->mm->context.vdso; + + /* Are we from a system call? */ + if (regs->regs[0]) { + switch (regs->regs[4]) { + case -ERESTART_RESTARTBLOCK: + case -ERESTARTNOHAND: + regs->regs[4] = -EINTR; + break; + case -ERESTARTSYS: + if (!(ksig->ka.sa.sa_flags & SA_RESTART)) { + regs->regs[4] = -EINTR; + break; + } + fallthrough; + case -ERESTARTNOINTR: + regs->regs[4] = regs->orig_a0; + regs->csr_epc -= 4; + } + + regs->regs[0] = 0; /* Don't deal with this again. */ + } + + rseq_signal_deliver(ksig, regs); + + ret = setup_rt_frame(vdso + abi->vdso->offset_sigreturn, ksig, regs, oldset); + + signal_setup_done(ret, ksig, 0); +} + +void arch_do_signal_or_restart(struct pt_regs *regs, bool has_signal) +{ + struct ksignal ksig; + + if (has_signal && get_signal(&ksig)) { + /* Whee! Actually deliver the signal. */ + handle_signal(&ksig, regs); + return; + } + + /* Are we from a system call? */ + if (regs->regs[0]) { + switch (regs->regs[4]) { + case -ERESTARTNOHAND: + case -ERESTARTSYS: + case -ERESTARTNOINTR: + regs->regs[4] = regs->orig_a0; + regs->csr_epc -= 4; + break; + + case -ERESTART_RESTARTBLOCK: + regs->regs[4] = regs->orig_a0; + regs->regs[11] = current->thread.abi->restart; + regs->csr_epc -= 4; + break; + } + regs->regs[0] = 0; /* Don't deal with this again. */ + } + + /* + * If there's no signal to deliver, we just put the saved sigmask + * back + */ + restore_saved_sigmask(); +} + +static int signal_setup(void) +{ + if (cpu_has_fpu) { + save_fp_context = save_hw_fp_context; + restore_fp_context = restore_hw_fp_context; + } else { + save_fp_context = copy_fp_to_sigcontext; + restore_fp_context = copy_fp_from_sigcontext; + } + + return 0; +} + +arch_initcall(signal_setup);