[RFC PATCH v3 26/37] kvx: Add signal handling support

ysionneau
2024-07-22T09:43:48Z

From: Yann Sionneau <ysionneau@kalrayinc.com>

Add sigcontext definition and signal handling support for kvx.

Co-developed-by: Clement Leger <clement@clement-leger.fr>
Signed-off-by: Clement Leger <clement@clement-leger.fr>
Co-developed-by: Jules Maselbas <jmaselbas@zdiv.net>
Signed-off-by: Jules Maselbas <jmaselbas@zdiv.net>
Co-developed-by: Julian Vetter <jvetter@kalrayinc.com>
Signed-off-by: Julian Vetter <jvetter@kalrayinc.com>
Signed-off-by: Yann Sionneau <ysionneau@kalrayinc.com>
---

Notes:
V1 -> V2: Use read_thread_flags() as suggested by Mark Rutland
V2 -> V3:
- Updated to use generic functions (e.g., arch_do_signal_or_restart)
- Remove do_work_pending (now done by generic exit_to_user_mode_loop)
---
arch/kvx/include/uapi/asm/sigcontext.h | 16 ++
arch/kvx/kernel/signal.c | 252 +++++++++++++++++++++++++
arch/kvx/kernel/vdso.c | 87 +++++++++
3 files changed, 355 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 0000000000000..a26688fe8571f
--- /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_regs_struct 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 0000000000000..f49c66aef2df6
--- /dev/null
+++ b/arch/kvx/kernel/signal.c
@@ -0,0 +1,252 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2017-2023 Kalray Inc.
+ * Author(s): Clement Leger
+ */
+
+#include <linux/bug.h>
+#include <linux/entry-common.h>
+#include <linux/syscalls.h>
+
+#include <asm/ucontext.h>
+#include <asm/processor.h>
+#include <asm/cacheflush.h>
+#include <asm/syscall.h>
+#include <asm/syscalls.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)
+{
+ bool stepping;
+ sigset_t *oldset = sigmask_to_save();
+ int ret;
+
+ /* Are we in 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;
+ }
+ }
+
+ /*
+ * If TF is set due to a debugger (TIF_FORCED_TF), clear TF now
+ * so that register information in the sigcontext is correct and
+ * then notify the tracer before entering the signal handler.
+ */
+ stepping = test_thread_flag(TIF_SINGLESTEP);
+ if (stepping)
+ user_disable_single_step(current);
+
+ ret = setup_rt_frame(ksig, oldset, regs);
+
+ signal_setup_done(ret, ksig, stepping);
+}
+
+void arch_do_signal_or_restart(struct pt_regs *regs)
+{
+ struct ksignal ksig;
+
+ if (get_signal(&ksig)) {
+ handle_signal(&ksig, regs);
+ return;
+ }
+
+ /* Did we come 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();
+}
diff --git a/arch/kvx/kernel/vdso.c b/arch/kvx/kernel/vdso.c
new file mode 100644
index 0000000000000..1515de15eb31b
--- /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;
+}
--
2.45.2