[RFC PATCH v2 22/31] kvx: Add signal handling support

Add sigcontext definition and signal handling support for kvx. Co-developed-by: Clement Leger <clement(a)clement-leger.fr&gt; Signed-off-by: Clement Leger <clement(a)clement-leger.fr&gt; Co-developed-by: Jules Maselbas <jmaselbas(a)kalray.eu&gt; Signed-off-by: Jules Maselbas <jmaselbas(a)kalray.eu&gt; Co-developed-by: Julian Vetter <jvetter(a)kalray.eu&gt; Signed-off-by: Julian Vetter <jvetter(a)kalray.eu&gt; Co-developed-by: Yann Sionneau <ysionneau(a)kalray.eu&gt; Signed-off-by: Yann Sionneau <ysionneau(a)kalray.eu&gt; --- Notes: V1 -> V2: - use read_thread_flags() as suggested by Mark Rutland arch/kvx/include/uapi/asm/sigcontext.h | 16 ++ arch/kvx/kernel/signal.c | 265 +++++++++++++++++++++++++ arch/kvx/kernel/vdso.c | 87 ++++++++ 3 files changed, 368 insertions(+) create mode 100644 arch/kvx/include/uapi/asm/sigcontext.h create mode 100644 arch/kvx/kernel/signal.c create mode 100644 arch/kvx/kernel/vdso.c diff --git a/arch/kvx/include/uapi/asm/sigcontext.h b/arch/kvx/include/uapi/asm/sigcontext.h new file mode 100644 index 000000000000..97ab4f78152a --- /dev/null +++ b/arch/kvx/include/uapi/asm/sigcontext.h @@ -0,0 +1,16 @@ +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note */ +/* + * Copyright (C) 2017-2023 Kalray Inc. + * Author(s): Clement Leger + */ + +#ifndef _UAPI_ASM_KVX_SIGCONTEXT_H +#define _UAPI_ASM_KVX_SIGCONTEXT_H + +#include <asm/ptrace.h> + +struct sigcontext { + struct user_pt_regs sc_regs; +}; + +#endif /* _UAPI_ASM_KVX_SIGCONTEXT_H */ diff --git a/arch/kvx/kernel/signal.c b/arch/kvx/kernel/signal.c new file mode 100644 index 000000000000..5bd63d14f43e --- /dev/null +++ b/arch/kvx/kernel/signal.c @@ -0,0 +1,265 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2017-2023 Kalray Inc. + * Author(s): Clement Leger + */ + +#include <linux/bug.h> +#include <linux/syscalls.h> + +#include <asm/ucontext.h> +#include <asm/processor.h> +#include <asm/cacheflush.h> +#include <linux/resume_user_mode.h> + +struct rt_sigframe { + struct siginfo info; + struct ucontext uc; +}; + +int __init setup_syscall_sigreturn_page(void *sigpage_addr) +{ + unsigned int frame_size = (uintptr_t) &user_scall_rt_sigreturn_end - + (uintptr_t) &user_scall_rt_sigreturn; + + /* Copy the sigreturn scall implementation */ + memcpy(sigpage_addr, &user_scall_rt_sigreturn, frame_size); + + flush_icache_range((unsigned long) sigpage_addr, + (unsigned long) sigpage_addr + frame_size); + + return 0; +} + +static long restore_sigcontext(struct pt_regs *regs, + struct sigcontext __user *sc) +{ + long err; + + /* sc_regs is structured the same as the start of pt_regs */ + err = __copy_from_user(regs, &sc->sc_regs, sizeof(sc->sc_regs)); + + return err; +} + +long _sys_rt_sigreturn(void) +{ + struct pt_regs *regs = current_pt_regs(); + struct rt_sigframe __user *frame; + struct task_struct *task; + sigset_t set; + + current->restart_block.fn = do_no_restart_syscall; + + frame = (struct rt_sigframe __user *) user_stack_pointer(regs); + + /* + * Stack is not aligned but should be ! + * User probably did some malicious things. + */ + if (user_stack_pointer(regs) & STACK_ALIGN_MASK) + goto badframe; + + if (!access_ok(frame, sizeof(*frame))) + goto badframe; + + /* Restore sigmask */ + if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set))) + goto badframe; + + set_current_blocked(&set); + + if (restore_sigcontext(regs, &frame->uc.uc_mcontext)) + goto badframe; + + if (restore_altstack(&frame->uc.uc_stack)) + goto badframe; + + return regs->r0; + +badframe: + task = current; + if (show_unhandled_signals) { + pr_info_ratelimited( + "%s[%d]: bad frame in %s: frame=%p pc=%p sp=%p\n", + task->comm, task_pid_nr(task), __func__, + frame, (void *) instruction_pointer(regs), + (void *) user_stack_pointer(regs)); + } + force_sig(SIGSEGV); + return 0; +} + + +static long setup_sigcontext(struct rt_sigframe __user *frame, + struct pt_regs *regs) +{ + struct sigcontext __user *sc = &frame->uc.uc_mcontext; + long err; + + /* sc_regs is structured the same as the start of pt_regs */ + err = __copy_to_user(&sc->sc_regs, regs, sizeof(sc->sc_regs)); + + return err; +} + +static inline void __user *get_sigframe(struct ksignal *ksig, + struct pt_regs *regs, size_t framesize) +{ + unsigned long sp; + /* Default to using normal stack */ + sp = regs->sp; + + /* + * If we are on the alternate signal stack and would overflow it, don't. + * Return an always-bogus address instead so we will die with SIGSEGV. + */ + if (on_sig_stack(sp) && !likely(on_sig_stack(sp - framesize))) + return (void __user __force *)(-1UL); + + /* This is the X/Open sanctioned signal stack switching. */ + sp = sigsp(sp, ksig) - framesize; + + /* Align the stack frame on 16bytes */ + sp &= ~STACK_ALIGN_MASK; + + return (void __user *)sp; +} + +/* TODO: Use VDSO when ready ! */ +static int setup_rt_frame(struct ksignal *ksig, sigset_t *set, + struct pt_regs *regs) +{ + unsigned long sigpage = current->mm->context.sigpage; + struct rt_sigframe __user *frame; + long err = 0; + + frame = get_sigframe(ksig, regs, sizeof(*frame)); + if (!access_ok(frame, sizeof(*frame))) + return -EFAULT; + + err |= copy_siginfo_to_user(&frame->info, &ksig->info); + + /* Create the ucontext. */ + err |= __put_user(0, &frame->uc.uc_flags); + err |= __put_user(NULL, &frame->uc.uc_link); + err |= __save_altstack(&frame->uc.uc_stack, user_stack_pointer(regs)); + err |= setup_sigcontext(frame, regs); + err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set)); + if (err) + return -EFAULT; + + /* + * When returning from the handler, we want to jump to the + * sigpage which will execute the sigreturn scall. + */ + regs->ra = sigpage; + /* Return to signal handler */ + regs->spc = (unsigned long)ksig->ka.sa.sa_handler; + regs->sp = (unsigned long) frame; + + /* Parameters for signal handler */ + regs->r0 = ksig->sig; /* r0: signal number */ + regs->r1 = (unsigned long)(&frame->info); /* r1: siginfo pointer */ + regs->r2 = (unsigned long)(&frame->uc); /* r2: ucontext pointer */ + + return 0; +} + +static void handle_signal(struct ksignal *ksig, struct pt_regs *regs) +{ + sigset_t *oldset = sigmask_to_save(); + int ret; + + /* Are we from a system call? */ + if (in_syscall(regs)) { + /* If so, check system call restarting.. */ + switch (regs->r0) { + case -ERESTART_RESTARTBLOCK: + case -ERESTARTNOHAND: + regs->r0 = -EINTR; + break; + case -ERESTARTSYS: + if (!(ksig->ka.sa.sa_flags & SA_RESTART)) { + regs->r0 = -EINTR; + break; + } + fallthrough; + case -ERESTARTNOINTR: + regs->r0 = regs->orig_r0; + regs->spc -= 0x4; + break; + } + } + + ret = setup_rt_frame(ksig, oldset, regs); + + signal_setup_done(ret, ksig, 0); +} + +asmlinkage void do_signal(struct pt_regs *regs) +{ + struct ksignal ksig; + + if (get_signal(&ksig)) { + handle_signal(&ksig, regs); + return; + } + + /* Are we from a system call? */ + if (in_syscall(regs)) { + /* + * If we are here, this means there is no handler + * present and we must restart the syscall. + */ + switch (regs->r0) { + case -ERESTART_RESTARTBLOCK: + /* Modify the syscall number in order to restart it */ + regs->r6 = __NR_restart_syscall; + fallthrough; + case -ERESTARTNOHAND: + case -ERESTARTSYS: + case -ERESTARTNOINTR: + /* We are restarting the syscall */ + regs->r0 = regs->orig_r0; + /* + * scall instruction isn't bundled with anything else, + * so we can just revert the spc to restart the syscall. + */ + regs->spc -= 0x4; + break; + } + } + + /* + * If there's no signal to deliver, we just put the saved sigmask + * back. + */ + restore_saved_sigmask(); +} + + +asmlinkage void do_work_pending(struct pt_regs *regs, + unsigned long thread_flags) +{ + /* We are called with IRQs disabled */ + trace_hardirqs_off(); + + do { + if (thread_flags & _TIF_NEED_RESCHED) { + schedule(); + } else { + local_irq_enable(); + if (thread_flags & (_TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL)) + do_signal(regs); + + if (thread_flags & _TIF_NOTIFY_RESUME) { + clear_thread_flag(TIF_NOTIFY_RESUME); + resume_user_mode_work(regs); + } + } + local_irq_disable(); + thread_flags = read_thread_flags(); + } while (thread_flags & _TIF_WORK_MASK); +} + diff --git a/arch/kvx/kernel/vdso.c b/arch/kvx/kernel/vdso.c new file mode 100644 index 000000000000..1515de15eb31 --- /dev/null +++ b/arch/kvx/kernel/vdso.c @@ -0,0 +1,87 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2017-2023 Kalray Inc. + * Author(s): Clement Leger + */ + +#include <linux/mm.h> +#include <linux/vmalloc.h> +#include <linux/binfmts.h> + +#include <asm/syscall.h> + +static struct page *signal_page; + +static int __init init_sigreturn(void) +{ + struct page *sigpage; + void *mapped_sigpage; + int err; + + sigpage = alloc_page(GFP_KERNEL); + if (!sigpage) + panic("Cannot allocate sigreturn page"); + + mapped_sigpage = vmap(&sigpage, 1, 0, PAGE_KERNEL); + if (!mapped_sigpage) + panic("Cannot map sigreturn page"); + + clear_page(mapped_sigpage); + + err = setup_syscall_sigreturn_page(mapped_sigpage); + if (err) + panic("Cannot set signal return syscall, err: %x.", err); + + vunmap(mapped_sigpage); + + signal_page = sigpage; + + return 0; +} +arch_initcall(init_sigreturn); + +static int sigpage_mremap(const struct vm_special_mapping *sm, + struct vm_area_struct *new_vma) +{ + current->mm->context.sigpage = new_vma->vm_start; + return 0; +} + +static const struct vm_special_mapping sigpage_mapping = { + .name = "[sigpage]", + .pages = &signal_page, + .mremap = sigpage_mremap, +}; + +int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp) +{ + int ret = 0; + unsigned long addr; + struct mm_struct *mm = current->mm; + struct vm_area_struct *vma; + + mmap_write_lock(mm); + + addr = get_unmapped_area(NULL, STACK_TOP, PAGE_SIZE, 0, 0); + if (IS_ERR_VALUE(addr)) { + ret = addr; + goto up_fail; + } + + vma = _install_special_mapping( + mm, + addr, + PAGE_SIZE, + VM_READ|VM_EXEC|VM_MAYREAD|VM_MAYEXEC, + &sigpage_mapping); + if (IS_ERR(vma)) { + ret = PTR_ERR(vma); + goto up_fail; + } + + mm->context.sigpage = addr; + +up_fail: + mmap_write_unlock(mm); + return ret; +} -- 2.37.2