[PATCH V6 18/20] riscv: compat: signal: Add rt_frame implementation

guoren
2022-02-24T08:57:45Z

Implement compat_setup_rt_frame for sigcontext save & restore. The
main process is the same with signal, but the rv32 pt_regs' size
is different from rv64's, so we needs convert them.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>
Cc: Arnd Bergmann <arnd@arndb.de>
---
arch/riscv/kernel/Makefile | 1 +
arch/riscv/kernel/compat_signal.c | 243 ++++++++++++++++++++++++++++++
arch/riscv/kernel/signal.c | 13 +-
3 files changed, 256 insertions(+), 1 deletion(-)
create mode 100644 arch/riscv/kernel/compat_signal.c

diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 88e79f481c21..a46f9807c59e 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -67,4 +67,5 @@ obj-$(CONFIG_JUMP_LABEL) += jump_label.o

obj-$(CONFIG_EFI) += efi.o
obj-$(CONFIG_COMPAT) += compat_syscall_table.o
+obj-$(CONFIG_COMPAT) += compat_signal.o
obj-$(CONFIG_COMPAT) += compat_vdso/
diff --git a/arch/riscv/kernel/compat_signal.c b/arch/riscv/kernel/compat_signal.c
new file mode 100644
index 000000000000..7041742ded08
--- /dev/null
+++ b/arch/riscv/kernel/compat_signal.c
@@ -0,0 +1,243 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/compat.h>
+#include <linux/signal.h>
+#include <linux/uaccess.h>
+#include <linux/syscalls.h>
+#include <linux/tracehook.h>
+#include <linux/linkage.h>
+
+#include <asm/ucontext.h>
+#include <asm/vdso.h>
+#include <asm/switch_to.h>
+#include <asm/csr.h>
+
+#define COMPAT_DEBUG_SIG 0
+
+struct compat_sigcontext {
+ struct compat_user_regs_struct sc_regs;
+ union __riscv_fp_state sc_fpregs;
+};
+
+struct compat_ucontext {
+ compat_ulong_t uc_flags;
+ struct compat_ucontext *uc_link;
+ compat_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 compat_sigcontext uc_mcontext;
+};
+
+struct compat_rt_sigframe {
+ struct compat_siginfo info;
+ struct compat_ucontext uc;
+};
+
+#ifdef CONFIG_FPU
+static long compat_restore_fp_state(struct pt_regs *regs,
+ union __riscv_fp_state __user *sc_fpregs)
+{
+ long err;
+ struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
+ size_t i;
+
+ err = __copy_from_user(&current->thread.fstate, state, sizeof(*state));
+ if (unlikely(err))
+ return err;
+
+ fstate_restore(current, regs);
+
+ /* We support no other extension state at this time. */
+ for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
+ u32 value;
+
+ err = __get_user(value, &sc_fpregs->q.reserved[i]);
+ if (unlikely(err))
+ break;
+ if (value != 0)
+ return -EINVAL;
+ }
+
+ return err;
+}
+
+static long compat_save_fp_state(struct pt_regs *regs,
+ union __riscv_fp_state __user *sc_fpregs)
+{
+ long err;
+ struct __riscv_d_ext_state __user *state = &sc_fpregs->d;
+ size_t i;
+
+ fstate_save(current, regs);
+ err = __copy_to_user(state, &current->thread.fstate, sizeof(*state));
+ if (unlikely(err))
+ return err;
+
+ /* We support no other extension state at this time. */
+ for (i = 0; i < ARRAY_SIZE(sc_fpregs->q.reserved); i++) {
+ err = __put_user(0, &sc_fpregs->q.reserved[i]);
+ if (unlikely(err))
+ break;
+ }
+
+ return err;
+}
+#else
+#define compat_save_fp_state(task, regs) (0)
+#define compat_restore_fp_state(task, regs) (0)
+#endif
+
+static long compat_restore_sigcontext(struct pt_regs *regs,
+ struct compat_sigcontext __user *sc)
+{
+ long err;
+ struct compat_user_regs_struct cregs;
+
+ /* sc_regs is structured the same as the start of pt_regs */
+ err = __copy_from_user(&cregs, &sc->sc_regs, sizeof(sc->sc_regs));
+
+ cregs_to_regs(&cregs, regs);
+
+ /* Restore the floating-point state. */
+ if (has_fpu())
+ err |= compat_restore_fp_state(regs, &sc->sc_fpregs);
+ return err;
+}
+
+COMPAT_SYSCALL_DEFINE0(rt_sigreturn)
+{
+ struct pt_regs *regs = current_pt_regs();
+ struct compat_rt_sigframe __user *frame;
+ struct task_struct *task;
+ sigset_t set;
+
+ /* Always make any pending restarted system calls return -EINTR */
+ current->restart_block.fn = do_no_restart_syscall;
+
+ frame = (struct compat_rt_sigframe __user *)regs->sp;
+
+ if (!access_ok(frame, sizeof(*frame)))
+ goto badframe;
+
+ if (__copy_from_user(&set, &frame->uc.uc_sigmask, sizeof(set)))
+ goto badframe;
+
+ set_current_blocked(&set);
+
+ if (compat_restore_sigcontext(regs, &frame->uc.uc_mcontext))
+ goto badframe;
+
+ if (compat_restore_altstack(&frame->uc.uc_stack))
+ goto badframe;
+
+ return regs->a0;
+
+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 *)regs->epc, (void *)regs->sp);
+ }
+ force_sig(SIGSEGV);
+ return 0;
+}
+
+static long compat_setup_sigcontext(struct compat_rt_sigframe __user *frame,
+ struct pt_regs *regs)
+{
+ struct compat_sigcontext __user *sc = &frame->uc.uc_mcontext;
+ struct compat_user_regs_struct cregs;
+ long err;
+
+ regs_to_cregs(&cregs, regs);
+
+ /* sc_regs is structured the same as the start of pt_regs */
+ err = __copy_to_user(&sc->sc_regs, &cregs, sizeof(sc->sc_regs));
+ /* Save the floating-point state. */
+ if (has_fpu())
+ err |= compat_save_fp_state(regs, &sc->sc_fpregs);
+ return err;
+}
+
+static inline void __user *compat_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. */
+ sp &= ~0xfUL;
+
+ return (void __user *)sp;
+}
+
+int compat_setup_rt_frame(struct ksignal *ksig, sigset_t *set,
+ struct pt_regs *regs)
+{
+ struct compat_rt_sigframe __user *frame;
+ long err = 0;
+
+ frame = compat_get_sigframe(ksig, regs, sizeof(*frame));
+ if (!access_ok(frame, sizeof(*frame)))
+ return -EFAULT;
+
+ err |= copy_siginfo_to_user32(&frame->info, &ksig->info);
+
+ /* Create the ucontext. */
+ err |= __put_user(0, &frame->uc.uc_flags);
+ err |= __put_user(NULL, &frame->uc.uc_link);
+ err |= __compat_save_altstack(&frame->uc.uc_stack, regs->sp);
+ err |= compat_setup_sigcontext(frame, regs);
+ err |= __copy_to_user(&frame->uc.uc_sigmask, set, sizeof(*set));
+ if (err)
+ return -EFAULT;
+
+ regs->ra = (unsigned long)COMPAT_VDSO_SYMBOL(
+ current->mm->context.vdso, rt_sigreturn);
+
+ /*
+ * Set up registers for signal handler.
+ * Registers that we don't modify keep the value they had from
+ * user-space at the time we took the signal.
+ * We always pass siginfo and mcontext, regardless of SA_SIGINFO,
+ * since some things rely on this (e.g. glibc's debug/segfault.c).
+ */
+ regs->epc = (unsigned long)ksig->ka.sa.sa_handler;
+ regs->sp = (unsigned long)frame;
+ regs->a0 = ksig->sig; /* a0: signal number */
+ regs->a1 = (unsigned long)(&frame->info); /* a1: siginfo pointer */
+ regs->a2 = (unsigned long)(&frame->uc); /* a2: ucontext pointer */
+
+#if COMPAT_DEBUG_SIG
+ pr_info("SIG deliver (%s:%d): sig=%d pc=%p ra=%p sp=%p\n",
+ current->comm, task_pid_nr(current), ksig->sig,
+ (void *)regs->epc, (void *)regs->ra, frame);
+#endif
+
+ return 0;
+}
diff --git a/arch/riscv/kernel/signal.c b/arch/riscv/kernel/signal.c
index c2d5ecbe5526..27d8f39228c4 100644
--- a/arch/riscv/kernel/signal.c
+++ b/arch/riscv/kernel/signal.c
@@ -6,6 +6,7 @@
* Copyright (C) 2012 Regents of the University of California
*/

+#include <linux/compat.h>
#include <linux/signal.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
@@ -229,6 +230,11 @@ static int setup_rt_frame(struct ksignal *ksig, sigset_t *set,
return 0;
}

+#ifdef CONFIG_COMPAT
+extern int compat_setup_rt_frame(struct ksignal *ksig, sigset_t *set,
+ struct pt_regs *regs);
+#endif
+
static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
{
sigset_t *oldset = sigmask_to_save();
@@ -258,8 +264,13 @@ static void handle_signal(struct ksignal *ksig, struct pt_regs *regs)
}
}

+#ifdef CONFIG_COMPAT
/* Set up the stack frame */
- ret = setup_rt_frame(ksig, oldset, regs);
+ if (is_compat_task())
+ ret = compat_setup_rt_frame(ksig, oldset, regs);
+ else
+#endif
+ ret = setup_rt_frame(ksig, oldset, regs);

signal_setup_done(ret, ksig, 0);
}
--
2.25.1