MIPS: Save MSA extended context around signals

It is desirable for signal handlers to be allowed to make use of MSA,
particularly if auto vectorisation is used when compiling a program.
The MSA context must therefore be saved & restored before & after
invoking the signal handler. Make use of the extended context structs
defined in the preceding patch to save MSA context after the sigframe
when appropriate.

[ralf@linux-mips.org: Fixed conflicts.]

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: Guenter Roeck <linux@roeck-us.net>
Cc: Matthew Fortune <matthew.fortune@imgtec.com>
Cc: Leonid Yegoshin <Leonid.Yegoshin@imgtec.com>
Cc: linux-kernel@vger.kernel.org
Cc: Richard Weinberger <richard@nod.at>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: Manuel Lauss <manuel.lauss@gmail.com>
Cc: Maciej W. Rozycki <macro@codesourcery.com>
Patchwork: https://patchwork.linux-mips.org/patch/10796/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 212 insertions, 15 deletions

diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 3101bafd3a9c..fa13a52713df 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -38,6 +38,7 @@
 #include <asm/vdso.h>
 #include <asm/dsp.h>
 #include <asm/inst.h>
+#include <asm/msa.h>
 
 #include "signal-common.h"
 
@@ -125,6 +126,168 @@ static int restore_hw_fp_context(void __user *sc)
 }
 
 /*
+ * Extended context handling.
+ */
+
+static inline void __user *sc_to_extcontext(void __user *sc)
+{
+	struct ucontext __user *uc;
+
+	/*
+	 * We can just pretend the sigcontext is always embedded in a struct
+	 * ucontext here, because the offset from sigcontext to extended
+	 * context is the same in the struct sigframe case.
+	 */
+	uc = container_of(sc, struct ucontext, uc_mcontext);
+	return &uc->uc_extcontext;
+}
+
+static int save_msa_extcontext(void __user *buf)
+{
+	struct msa_extcontext __user *msa = buf;
+	uint64_t val;
+	int i, err;
+
+	if (!thread_msa_context_live())
+		return 0;
+
+	/*
+	 * Ensure that we can't lose the live MSA context between checking
+	 * for it & writing it to memory.
+	 */
+	preempt_disable();
+
+	if (is_msa_enabled()) {
+		/*
+		 * There are no EVA versions of the vector register load/store
+		 * instructions, so MSA context has to be saved to kernel memory
+		 * and then copied to user memory. The save to kernel memory
+		 * should already have been done when handling scalar FP
+		 * context.
+		 */
+		BUG_ON(config_enabled(CONFIG_EVA));
+
+		err = __put_user(read_msa_csr(), &msa->csr);
+		err |= _save_msa_all_upper(&msa->wr);
+
+		preempt_enable();
+	} else {
+		preempt_enable();
+
+		err = __put_user(current->thread.fpu.msacsr, &msa->csr);
+
+		for (i = 0; i < NUM_FPU_REGS; i++) {
+			val = get_fpr64(&current->thread.fpu.fpr[i], 1);
+			err |= __put_user(val, &msa->wr[i]);
+		}
+	}
+
+	err |= __put_user(MSA_EXTCONTEXT_MAGIC, &msa->ext.magic);
+	err |= __put_user(sizeof(*msa), &msa->ext.size);
+
+	return err ? -EFAULT : sizeof(*msa);
+}
+
+static int restore_msa_extcontext(void __user *buf, unsigned int size)
+{
+	struct msa_extcontext __user *msa = buf;
+	unsigned long long val;
+	unsigned int csr;
+	int i, err;
+
+	if (size != sizeof(*msa))
+		return -EINVAL;
+
+	err = get_user(csr, &msa->csr);
+	if (err)
+		return err;
+
+	preempt_disable();
+
+	if (is_msa_enabled()) {
+		/*
+		 * There are no EVA versions of the vector register load/store
+		 * instructions, so MSA context has to be copied to kernel
+		 * memory and later loaded to registers. The same is true of
+		 * scalar FP context, so FPU & MSA should have already been
+		 * disabled whilst handling scalar FP context.
+		 */
+		BUG_ON(config_enabled(CONFIG_EVA));
+
+		write_msa_csr(csr);
+		err |= _restore_msa_all_upper(&msa->wr);
+		preempt_enable();
+	} else {
+		preempt_enable();
+
+		current->thread.fpu.msacsr = csr;
+
+		for (i = 0; i < NUM_FPU_REGS; i++) {
+			err |= __get_user(val, &msa->wr[i]);
+			set_fpr64(&current->thread.fpu.fpr[i], 1, val);
+		}
+	}
+
+	return err;
+}
+
+static int save_extcontext(void __user *buf)
+{
+	int sz;
+
+	sz = save_msa_extcontext(buf);
+	if (sz < 0)
+		return sz;
+	buf += sz;
+
+	/* If no context was saved then trivially return */
+	if (!sz)
+		return 0;
+
+	/* Write the end marker */
+	if (__put_user(END_EXTCONTEXT_MAGIC, (u32 *)buf))
+		return -EFAULT;
+
+	sz += sizeof(((struct extcontext *)NULL)->magic);
+	return sz;
+}
+
+static int restore_extcontext(void __user *buf)
+{
+	struct extcontext ext;
+	int err;
+
+	while (1) {
+		err = __get_user(ext.magic, (unsigned int *)buf);
+		if (err)
+			return err;
+
+		if (ext.magic == END_EXTCONTEXT_MAGIC)
+			return 0;
+
+		err = __get_user(ext.size, (unsigned int *)(buf
+			+ offsetof(struct extcontext, size)));
+		if (err)
+			return err;
+
+		switch (ext.magic) {
+		case MSA_EXTCONTEXT_MAGIC:
+			err = restore_msa_extcontext(buf, ext.size);
+			break;
+
+		default:
+			err = -EINVAL;
+			break;
+		}
+
+		if (err)
+			return err;
+
+		buf += ext.size;
+	}
+}
+
+/*
  * Helper routines
  */
 int protected_save_fp_context(void __user *sc)
@@ -133,20 +296,17 @@ int protected_save_fp_context(void __user *sc)
 	uint64_t __user *fpregs = sc + abi->off_sc_fpregs;
 	uint32_t __user *csr = sc + abi->off_sc_fpc_csr;
 	uint32_t __user *used_math = sc + abi->off_sc_used_math;
-	unsigned int used;
+	unsigned int used, ext_sz;
 	int err;
 
 	used = used_math() ? USED_FP : 0;
-	if (used) {
-		if (!test_thread_flag(TIF_32BIT_FPREGS))
-			used |= USED_FR1;
-		if (test_thread_flag(TIF_HYBRID_FPREGS))
-			used |= USED_HYBRID_FPRS;
-	}
+	if (!used)
+		goto fp_done;
 
-	err = __put_user(used, used_math);
-	if (err || !(used & USED_FP))
-		return err;
+	if (!test_thread_flag(TIF_32BIT_FPREGS))
+		used |= USED_FR1;
+	if (test_thread_flag(TIF_HYBRID_FPREGS))
+		used |= USED_HYBRID_FPRS;
 
 	/*
 	 * EVA does not have userland equivalents of ldc1 or sdc1, so
@@ -171,10 +331,16 @@ int protected_save_fp_context(void __user *sc)
 			__put_user(0, &fpregs[31]) |
 			__put_user(0, csr);
 		if (err)
-			break;	/* really bad sigcontext */
+			return err;	/* really bad sigcontext */
 	}
 
-	return err;
+fp_done:
+	ext_sz = err = save_extcontext(sc_to_extcontext(sc));
+	if (err < 0)
+		return err;
+	used |= ext_sz ? USED_EXTCONTEXT : 0;
+
+	return __put_user(used, used_math);
 }
 
 int protected_restore_fp_context(void __user *sc)
@@ -184,7 +350,7 @@ int protected_restore_fp_context(void __user *sc)
 	uint32_t __user *csr = sc + abi->off_sc_fpc_csr;
 	uint32_t __user *used_math = sc + abi->off_sc_used_math;
 	unsigned int used;
-	int err, sig, tmp __maybe_unused;
+	int err, sig = 0, tmp __maybe_unused;
 
 	err = __get_user(used, used_math);
 	conditional_used_math(used & USED_FP);
@@ -193,10 +359,12 @@ int protected_restore_fp_context(void __user *sc)
 	 * The signal handler may have used FPU; give it up if the program
 	 * doesn't want it following sigreturn.
 	 */
-	if (err || !(used & USED_FP)) {
+	if (err || !(used & USED_FP))
 		lose_fpu(0);
+	if (err)
 		return err;
-	}
+	if (!(used & USED_FP))
+		goto fp_done;
 
 	err = sig = fpcsr_pending(csr);
 	if (err < 0)
@@ -229,6 +397,10 @@ int protected_restore_fp_context(void __user *sc)
 			break;	/* really bad sigcontext */
 	}
 
+fp_done:
+	if (used & USED_EXTCONTEXT)
+		err |= restore_extcontext(sc_to_extcontext(sc));
+
 	return err ?: sig;
 }
 
@@ -268,6 +440,28 @@ int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 	return err;
 }
 
+static size_t extcontext_max_size(void)
+{
+	size_t sz = 0;
+
+	/*
+	 * The assumption here is that between this point & the point at which
+	 * the extended context is saved the size of the context should only
+	 * ever be able to shrink (if the task is preempted), but never grow.
+	 * That is, what this function returns is an upper bound on the size of
+	 * the extended context for the current task at the current time.
+	 */
+
+	if (thread_msa_context_live())
+		sz += sizeof(struct msa_extcontext);
+
+	/* If any context is saved then we'll append the end marker */
+	if (sz)
+		sz += sizeof(((struct extcontext *)NULL)->magic);
+
+	return sz;
+}
+
 int fpcsr_pending(unsigned int __user *fpcsr)
 {
 	int err, sig = 0;
@@ -324,6 +518,9 @@ void __user *get_sigframe(struct ksignal *ksig, struct pt_regs *regs,
 {
 	unsigned long sp;
 
+	/* Leave space for potential extended context */
+	frame_size += extcontext_max_size();
+
 	/* Default to using normal stack */
 	sp = regs->regs[29];