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Subject[PATCH v2 19/31] arm64: Signal handling support
Date
This patch adds support for signal handling. The sigreturn is done via
VDSO, introduced by a previous patch. The SA_RESTORER is still defined
as it is required for 32-bit (compat) support but it is not to be used
for 64-bit applications.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm64/include/asm/sigcontext.h | 69 ++++++
arch/arm64/include/asm/siginfo.h | 23 ++
arch/arm64/include/asm/signal.h | 24 ++
arch/arm64/include/asm/ucontext.h | 30 +++
arch/arm64/kernel/signal.c | 436 +++++++++++++++++++++++++++++++++++
5 files changed, 582 insertions(+), 0 deletions(-)
create mode 100644 arch/arm64/include/asm/sigcontext.h
create mode 100644 arch/arm64/include/asm/siginfo.h
create mode 100644 arch/arm64/include/asm/signal.h
create mode 100644 arch/arm64/include/asm/ucontext.h
create mode 100644 arch/arm64/kernel/signal.c

diff --git a/arch/arm64/include/asm/sigcontext.h b/arch/arm64/include/asm/sigcontext.h
new file mode 100644
index 0000000..573cec7
--- /dev/null
+++ b/arch/arm64/include/asm/sigcontext.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_SIGCONTEXT_H
+#define __ASM_SIGCONTEXT_H
+
+#include <linux/types.h>
+
+/*
+ * Signal context structure - contains all info to do with the state
+ * before the signal handler was invoked.
+ */
+struct sigcontext {
+ __u64 fault_address;
+ /* AArch64 registers */
+ __u64 regs[31];
+ __u64 sp;
+ __u64 pc;
+ __u64 pstate;
+ /* 4K reserved for FP/SIMD state and future expansion */
+ __u8 __reserved[4096] __attribute__((__aligned__(16)));
+};
+
+/*
+ * Header to be used at the beginning of structures extending the user
+ * context. Such structures must be placed after the rt_sigframe on the stack
+ * and be 16-byte aligned. The last structure must be a dummy one with the
+ * magic and size set to 0.
+ */
+struct _aarch64_ctx {
+ __u32 magic;
+ __u32 size;
+};
+
+#define FPSIMD_MAGIC 0x46508001
+
+struct fpsimd_context {
+ struct _aarch64_ctx head;
+ __u32 fpsr;
+ __u32 fpcr;
+ __uint128_t vregs[32];
+};
+
+#ifdef __KERNEL__
+/*
+ * Auxiliary context saved in the sigcontext.__reserved array. Not exported to
+ * user space as it will change with the addition of new context. User space
+ * should check the magic/size information.
+ */
+struct aux_context {
+ struct fpsimd_context fpsimd;
+ /* additional context to be added before "end" */
+ struct _aarch64_ctx end;
+};
+#endif
+
+#endif
diff --git a/arch/arm64/include/asm/siginfo.h b/arch/arm64/include/asm/siginfo.h
new file mode 100644
index 0000000..5a74a08
--- /dev/null
+++ b/arch/arm64/include/asm/siginfo.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_SIGINFO_H
+#define __ASM_SIGINFO_H
+
+#define __ARCH_SI_PREAMBLE_SIZE (4 * sizeof(int))
+
+#include <asm-generic/siginfo.h>
+
+#endif
diff --git a/arch/arm64/include/asm/signal.h b/arch/arm64/include/asm/signal.h
new file mode 100644
index 0000000..8d1e723
--- /dev/null
+++ b/arch/arm64/include/asm/signal.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_SIGNAL_H
+#define __ASM_SIGNAL_H
+
+/* Required for AArch32 compatibility. */
+#define SA_RESTORER 0x04000000
+
+#include <asm-generic/signal.h>
+
+#endif
diff --git a/arch/arm64/include/asm/ucontext.h b/arch/arm64/include/asm/ucontext.h
new file mode 100644
index 0000000..bde9607
--- /dev/null
+++ b/arch/arm64/include/asm/ucontext.h
@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+#ifndef __ASM_UCONTEXT_H
+#define __ASM_UCONTEXT_H
+
+struct ucontext {
+ unsigned long uc_flags;
+ struct ucontext *uc_link;
+ stack_t uc_stack;
+ sigset_t uc_sigmask;
+ /* glibc uses a 1024-bit sigset_t */
+ __u8 __unused[(1024 - sizeof(sigset_t)) / 8];
+ /* last for future expansion */
+ struct sigcontext uc_mcontext;
+};
+
+#endif /* __ASM_UCONTEXT_H */
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
new file mode 100644
index 0000000..a8f29d2
--- /dev/null
+++ b/arch/arm64/kernel/signal.c
@@ -0,0 +1,436 @@
+/*
+ * Based on arch/arm/kernel/signal.c
+ *
+ * Copyright (C) 1995-2009 Russell King
+ * Copyright (C) 2012 ARM Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <linux/errno.h>
+#include <linux/signal.h>
+#include <linux/personality.h>
+#include <linux/freezer.h>
+#include <linux/uaccess.h>
+#include <linux/tracehook.h>
+#include <linux/ratelimit.h>
+
+#include <asm/debug-monitors.h>
+#include <asm/elf.h>
+#include <asm/cacheflush.h>
+#include <asm/ucontext.h>
+#include <asm/unistd.h>
+#include <asm/fpsimd.h>
+#include <asm/signal32.h>
+#include <asm/vdso.h>
+
+/*
+ * Do a signal return; undo the signal stack. These are aligned to 128-bit.
+ */
+struct rt_sigframe {
+ struct siginfo info;
+ struct ucontext uc;
+};
+
+static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
+{
+ struct fpsimd_state *fpsimd = &current->thread.fpsimd_state;
+ int err;
+
+ /* dump the hardware registers to the fpsimd_state structure */
+ fpsimd_save_state(fpsimd);
+
+ /* copy the FP and status/control registers */
+ err = __copy_to_user(ctx->vregs, fpsimd->vregs, sizeof(fpsimd->vregs));
+ __put_user_error(fpsimd->fpsr, &ctx->fpsr, err);
+ __put_user_error(fpsimd->fpcr, &ctx->fpcr, err);
+
+ /* copy the magic/size information */
+ __put_user_error(FPSIMD_MAGIC, &ctx->head.magic, err);
+ __put_user_error(sizeof(struct fpsimd_context), &ctx->head.size, err);
+
+ return err ? -EFAULT : 0;
+}
+
+static int restore_fpsimd_context(struct fpsimd_context __user *ctx)
+{
+ struct fpsimd_state fpsimd;
+ __u32 magic, size;
+ int err = 0;
+
+ /* check the magic/size information */
+ __get_user_error(magic, &ctx->head.magic, err);
+ __get_user_error(size, &ctx->head.size, err);
+ if (err)
+ return -EFAULT;
+ if (magic != FPSIMD_MAGIC || size != sizeof(struct fpsimd_context))
+ return -EINVAL;
+
+ /* copy the FP and status/control registers */
+ err = __copy_from_user(fpsimd.vregs, ctx->vregs,
+ sizeof(fpsimd.vregs));
+ __get_user_error(fpsimd.fpsr, &ctx->fpsr, err);
+ __get_user_error(fpsimd.fpcr, &ctx->fpcr, err);
+
+ /* load the hardware registers from the fpsimd_state structure */
+ if (!err) {
+ preempt_disable();
+ fpsimd_load_state(&fpsimd);
+ preempt_enable();
+ }
+
+ return err ? -EFAULT : 0;
+}
+
+static int restore_sigframe(struct pt_regs *regs,
+ struct rt_sigframe __user *sf)
+{
+ sigset_t set;
+ int i, err;
+ struct aux_context __user *aux =
+ (struct aux_context __user *)sf->uc.uc_mcontext.__reserved;
+
+ err = __copy_from_user(&set, &sf->uc.uc_sigmask, sizeof(set));
+ if (err == 0)
+ set_current_blocked(&set);
+
+ for (i = 0; i < 31; i++)
+ __get_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
+ err);
+ __get_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
+ __get_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
+ __get_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
+
+ /*
+ * Avoid sys_rt_sigreturn() restarting.
+ */
+ regs->syscallno = ~0UL;
+
+ err |= !valid_user_regs(&regs->user_regs);
+
+ if (err == 0)
+ err |= restore_fpsimd_context(&aux->fpsimd);
+
+ return err;
+}
+
+asmlinkage long sys_rt_sigreturn(struct pt_regs *regs)
+{
+ struct rt_sigframe __user *frame;
+
+ /* Always make any pending restarted system calls return -EINTR */
+ current_thread_info()->restart_block.fn = do_no_restart_syscall;
+
+ /*
+ * Since we stacked the signal on a 128-bit boundary, then 'sp' should
+ * be word aligned here.
+ */
+ if (regs->sp & 15)
+ goto badframe;
+
+ frame = (struct rt_sigframe __user *)regs->sp;
+
+ if (!access_ok(VERIFY_READ, frame, sizeof (*frame)))
+ goto badframe;
+
+ if (restore_sigframe(regs, frame))
+ goto badframe;
+
+ if (do_sigaltstack(&frame->uc.uc_stack,
+ NULL, regs->sp) == -EFAULT)
+ goto badframe;
+
+ return regs->regs[0];
+
+badframe:
+ if (show_unhandled_signals)
+ printk_ratelimited(KERN_INFO "%s[%d]: bad frame in %s: pc=%08llx sp=%08llx\n",
+ current->comm, task_pid_nr(current), __func__,
+ regs->pc, regs->sp);
+ force_sig(SIGSEGV, current);
+ return 0;
+}
+
+asmlinkage long sys_sigaltstack(const stack_t __user *uss, stack_t __user *uoss,
+ unsigned long sp)
+{
+ return do_sigaltstack(uss, uoss, sp);
+}
+
+static int setup_sigframe(struct rt_sigframe __user *sf,
+ struct pt_regs *regs, sigset_t *set)
+{
+ int i, err = 0;
+ struct aux_context __user *aux =
+ (struct aux_context __user *)sf->uc.uc_mcontext.__reserved;
+
+ for (i = 0; i < 31; i++)
+ __put_user_error(regs->regs[i], &sf->uc.uc_mcontext.regs[i],
+ err);
+ __put_user_error(regs->sp, &sf->uc.uc_mcontext.sp, err);
+ __put_user_error(regs->pc, &sf->uc.uc_mcontext.pc, err);
+ __put_user_error(regs->pstate, &sf->uc.uc_mcontext.pstate, err);
+
+ __put_user_error(current->thread.fault_address, &sf->uc.uc_mcontext.fault_address, err);
+
+ err |= __copy_to_user(&sf->uc.uc_sigmask, set, sizeof(*set));
+
+ if (err == 0)
+ err |= preserve_fpsimd_context(&aux->fpsimd);
+
+ /* set the "end" magic */
+ __put_user_error(0, &aux->end.magic, err);
+ __put_user_error(0, &aux->end.size, err);
+
+ return err;
+}
+
+static void __user *get_sigframe(struct k_sigaction *ka, struct pt_regs *regs,
+ int framesize)
+{
+ unsigned long sp, sp_top;
+ void __user *frame;
+
+ sp = sp_top = regs->sp;
+
+ /*
+ * This is the X/Open sanctioned signal stack switching.
+ */
+ if ((ka->sa.sa_flags & SA_ONSTACK) && !sas_ss_flags(sp))
+ sp = sp_top = current->sas_ss_sp + current->sas_ss_size;
+
+ /* room for stack frame (FP, LR) */
+ sp -= 16;
+
+ sp = (sp - framesize) & ~15;
+ frame = (void __user *)sp;
+
+ /*
+ * Check that we can actually write to the signal frame.
+ */
+ if (!access_ok(VERIFY_WRITE, frame, sp_top - sp))
+ frame = NULL;
+
+ return frame;
+}
+
+static int setup_return(struct pt_regs *regs, struct k_sigaction *ka,
+ void __user *frame, int usig)
+{
+ int err = 0;
+ __sigrestore_t sigtramp;
+ unsigned long __user *sp = (unsigned long __user *)regs->sp;
+
+ /* set up the stack frame */
+ __put_user_error(regs->regs[29], sp - 2, err);
+ __put_user_error(regs->regs[30], sp - 1, err);
+
+ regs->regs[0] = usig;
+ regs->regs[29] = regs->sp - 16;
+ regs->sp = (unsigned long)frame;
+ regs->pc = (unsigned long)ka->sa.sa_handler;
+
+ if (ka->sa.sa_flags & SA_RESTORER)
+ sigtramp = ka->sa.sa_restorer;
+ else
+ sigtramp = VDSO_SYMBOL(current->mm->context.vdso, sigtramp);
+
+ regs->regs[30] = (unsigned long)sigtramp;
+
+ return err;
+}
+
+static int setup_rt_frame(int usig, struct k_sigaction *ka, siginfo_t *info,
+ sigset_t *set, struct pt_regs *regs)
+{
+ struct rt_sigframe __user *frame;
+ stack_t stack;
+ int err = 0;
+
+ frame = get_sigframe(ka, regs, sizeof(*frame));
+ if (!frame)
+ return 1;
+
+ __put_user_error(0, &frame->uc.uc_flags, err);
+ __put_user_error(NULL, &frame->uc.uc_link, err);
+
+ memset(&stack, 0, sizeof(stack));
+ stack.ss_sp = (void __user *)current->sas_ss_sp;
+ stack.ss_flags = sas_ss_flags(regs->sp);
+ stack.ss_size = current->sas_ss_size;
+ err |= __copy_to_user(&frame->uc.uc_stack, &stack, sizeof(stack));
+
+ err |= setup_sigframe(frame, regs, set);
+ if (err == 0)
+ err = setup_return(regs, ka, frame, usig);
+
+ if (err == 0 && ka->sa.sa_flags & SA_SIGINFO) {
+ err |= copy_siginfo_to_user(&frame->info, info);
+ regs->regs[1] = (unsigned long)&frame->info;
+ regs->regs[2] = (unsigned long)&frame->uc;
+ }
+
+ return err;
+}
+
+static void setup_restart_syscall(struct pt_regs *regs)
+{
+ if (test_thread_flag(TIF_32BIT))
+ compat_setup_restart_syscall(regs);
+ else
+ regs->regs[8] = __NR_restart_syscall;
+}
+
+/*
+ * OK, we're invoking a handler
+ */
+static void handle_signal(unsigned long sig, struct k_sigaction *ka,
+ siginfo_t *info, struct pt_regs *regs)
+{
+ struct thread_info *thread = current_thread_info();
+ struct task_struct *tsk = current;
+ sigset_t *oldset = sigmask_to_save();
+ int usig = sig;
+ int ret;
+
+ /*
+ * translate the signal
+ */
+ if (usig < 32 && thread->exec_domain && thread->exec_domain->signal_invmap)
+ usig = thread->exec_domain->signal_invmap[usig];
+
+ /*
+ * Set up the stack frame
+ */
+ if (test_thread_flag(TIF_32BIT)) {
+ if (ka->sa.sa_flags & SA_SIGINFO)
+ ret = compat_setup_rt_frame(usig, ka, info, oldset,
+ regs);
+ else
+ ret = compat_setup_frame(usig, ka, oldset, regs);
+ } else {
+ ret = setup_rt_frame(usig, ka, info, oldset, regs);
+ }
+
+ /*
+ * Check that the resulting registers are actually sane.
+ */
+ ret |= !valid_user_regs(&regs->user_regs);
+
+ if (ret != 0) {
+ force_sigsegv(sig, tsk);
+ return;
+ }
+
+ /*
+ * Fast forward the stepping logic so we step into the signal
+ * handler.
+ */
+ user_fastforward_single_step(tsk);
+
+ signal_delivered(sig, info, ka, regs, 0);
+}
+
+/*
+ * Note that 'init' is a special process: it doesn't get signals it doesn't
+ * want to handle. Thus you cannot kill init even with a SIGKILL even by
+ * mistake.
+ *
+ * Note that we go through the signals twice: once to check the signals that
+ * the kernel can handle, and then we build all the user-level signal handling
+ * stack-frames in one go after that.
+ */
+static void do_signal(struct pt_regs *regs)
+{
+ unsigned long continue_addr = 0, restart_addr = 0;
+ struct k_sigaction ka;
+ siginfo_t info;
+ int signr, retval = 0;
+ int syscall = (int)regs->syscallno;
+
+ /*
+ * If we were from a system call, check for system call restarting...
+ */
+ if (syscall >= 0) {
+ continue_addr = regs->pc;
+ restart_addr = continue_addr - (compat_thumb_mode(regs) ? 2 : 4);
+ retval = regs->regs[0];
+
+ /*
+ * Avoid additional syscall restarting via ret_to_user.
+ */
+ regs->syscallno = ~0UL;
+
+ /*
+ * Prepare for system call restart. We do this here so that a
+ * debugger will see the already changed PC.
+ */
+ switch (retval) {
+ case -ERESTARTNOHAND:
+ case -ERESTARTSYS:
+ case -ERESTARTNOINTR:
+ case -ERESTART_RESTARTBLOCK:
+ regs->regs[0] = regs->orig_x0;
+ regs->pc = restart_addr;
+ break;
+ }
+ }
+
+ /*
+ * Get the signal to deliver. When running under ptrace, at this point
+ * the debugger may change all of our registers.
+ */
+ signr = get_signal_to_deliver(&info, &ka, regs, NULL);
+ if (signr > 0) {
+ /*
+ * Depending on the signal settings, we may need to revert the
+ * decision to restart the system call, but skip this if a
+ * debugger has chosen to restart at a different PC.
+ */
+ if (regs->pc == restart_addr &&
+ (retval == -ERESTARTNOHAND ||
+ retval == -ERESTART_RESTARTBLOCK ||
+ (retval == -ERESTARTSYS &&
+ !(ka.sa.sa_flags & SA_RESTART)))) {
+ regs->regs[0] = -EINTR;
+ regs->pc = continue_addr;
+ }
+
+ handle_signal(signr, &ka, &info, regs);
+ return;
+ }
+
+ /*
+ * Handle restarting a different system call. As above, if a debugger
+ * has chosen to restart at a different PC, ignore the restart.
+ */
+ if (syscall >= 0 && regs->pc == restart_addr) {
+ if (retval == -ERESTART_RESTARTBLOCK)
+ setup_restart_syscall(regs);
+ user_rewind_single_step(current);
+ }
+
+ restore_saved_sigmask();
+}
+
+asmlinkage void do_notify_resume(struct pt_regs *regs,
+ unsigned int thread_flags)
+{
+ if (thread_flags & _TIF_SIGPENDING)
+ do_signal(regs);
+
+ if (thread_flags & _TIF_NOTIFY_RESUME) {
+ clear_thread_flag(TIF_NOTIFY_RESUME);
+ tracehook_notify_resume(regs);
+ }
+}


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