MIPS: Save/restore MSA context around signals

This patch extends sigcontext in order to hold the most significant 64
bits of each vector register in addition to the MSA control & status
register. The least significant 64 bits are already saved as the scalar
FP context. This makes things a little awkward since the least & most
significant 64 bits of each vector register are not contiguous in
memory. Thus the copy_u & insert instructions are used to transfer the
values of the most significant 64 bits via GP registers.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6533/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 65 insertions, 8 deletions

diff --git a/arch/mips/kernel/signal.c b/arch/mips/kernel/signal.c
index 0f97c7dc54e6..fd61700409bc 100644
--- a/arch/mips/kernel/signal.c
+++ b/arch/mips/kernel/signal.c
@@ -30,6 +30,7 @@
 #include <linux/bitops.h>
 #include <asm/cacheflush.h>
 #include <asm/fpu.h>
+#include <asm/msa.h>
 #include <asm/sim.h>
 #include <asm/ucontext.h>
 #include <asm/cpu-features.h>
@@ -46,6 +47,9 @@ static int (*restore_fp_context)(struct sigcontext __user *sc);
 extern asmlinkage int _save_fp_context(struct sigcontext __user *sc);
 extern asmlinkage int _restore_fp_context(struct sigcontext __user *sc);
 
+extern asmlinkage int _save_msa_context(struct sigcontext __user *sc);
+extern asmlinkage int _restore_msa_context(struct sigcontext __user *sc);
+
 struct sigframe {
 	u32 sf_ass[4];		/* argument save space for o32 */
 	u32 sf_pad[2];		/* Was: signal trampoline */
@@ -95,19 +99,59 @@ static int copy_fp_from_sigcontext(struct sigcontext __user *sc)
 }
 
 /*
+ * These functions will save only the upper 64 bits of the vector registers,
+ * since the lower 64 bits have already been saved as the scalar FP context.
+ */
+static int copy_msa_to_sigcontext(struct sigcontext __user *sc)
+{
+	int i;
+	int err = 0;
+
+	for (i = 0; i < NUM_FPU_REGS; i++) {
+		err |=
+		    __put_user(get_fpr64(&current->thread.fpu.fpr[i], 1),
+			       &sc->sc_msaregs[i]);
+	}
+	err |= __put_user(current->thread.fpu.msacsr, &sc->sc_msa_csr);
+
+	return err;
+}
+
+static int copy_msa_from_sigcontext(struct sigcontext __user *sc)
+{
+	int i;
+	int err = 0;
+	u64 val;
+
+	for (i = 0; i < NUM_FPU_REGS; i++) {
+		err |= __get_user(val, &sc->sc_msaregs[i]);
+		set_fpr64(&current->thread.fpu.fpr[i], 1, val);
+	}
+	err |= __get_user(current->thread.fpu.msacsr, &sc->sc_msa_csr);
+
+	return err;
+}
+
+/*
  * Helper routines
  */
-static int protected_save_fp_context(struct sigcontext __user *sc)
+static int protected_save_fp_context(struct sigcontext __user *sc,
+				     unsigned used_math)
 {
 	int err;
+	bool save_msa = cpu_has_msa && (used_math & USEDMATH_MSA);
 	while (1) {
 		lock_fpu_owner();
 		if (is_fpu_owner()) {
 			err = save_fp_context(sc);
+			if (save_msa && !err)
+				err = _save_msa_context(sc);
 			unlock_fpu_owner();
 		} else {
 			unlock_fpu_owner();
 			err = copy_fp_to_sigcontext(sc);
+			if (save_msa && !err)
+				err = copy_msa_to_sigcontext(sc);
 		}
 		if (likely(!err))
 			break;
@@ -121,17 +165,28 @@ static int protected_save_fp_context(struct sigcontext __user *sc)
 	return err;
 }
 
-static int protected_restore_fp_context(struct sigcontext __user *sc)
+static int protected_restore_fp_context(struct sigcontext __user *sc,
+					unsigned used_math)
 {
 	int err, tmp __maybe_unused;
+	bool restore_msa = cpu_has_msa && (used_math & USEDMATH_MSA);
 	while (1) {
 		lock_fpu_owner();
 		if (is_fpu_owner()) {
 			err = restore_fp_context(sc);
+			if (restore_msa && !err) {
+				enable_msa();
+				err = _restore_msa_context(sc);
+			} else {
+				/* signal handler may have used MSA */
+				disable_msa();
+			}
 			unlock_fpu_owner();
 		} else {
 			unlock_fpu_owner();
 			err = copy_fp_from_sigcontext(sc);
+			if (!err && (used_math & USEDMATH_MSA))
+				err = copy_msa_from_sigcontext(sc);
 		}
 		if (likely(!err))
 			break;
@@ -172,7 +227,8 @@ int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 		err |= __put_user(rddsp(DSP_MASK), &sc->sc_dsp);
 	}
 
-	used_math = !!used_math();
+	used_math = used_math() ? USEDMATH_FP : 0;
+	used_math |= thread_msa_context_live() ? USEDMATH_MSA : 0;
 	err |= __put_user(used_math, &sc->sc_used_math);
 
 	if (used_math) {
@@ -180,7 +236,7 @@ int setup_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 		 * Save FPU state to signal context. Signal handler
 		 * will "inherit" current FPU state.
 		 */
-		err |= protected_save_fp_context(sc);
+		err |= protected_save_fp_context(sc, used_math);
 	}
 	return err;
 }
@@ -205,14 +261,14 @@ int fpcsr_pending(unsigned int __user *fpcsr)
 }
 
 static int
-check_and_restore_fp_context(struct sigcontext __user *sc)
+check_and_restore_fp_context(struct sigcontext __user *sc, unsigned used_math)
 {
 	int err, sig;
 
 	err = sig = fpcsr_pending(&sc->sc_fpc_csr);
 	if (err > 0)
 		err = 0;
-	err |= protected_restore_fp_context(sc);
+	err |= protected_restore_fp_context(sc, used_math);
 	return err ?: sig;
 }
 
@@ -252,9 +308,10 @@ int restore_sigcontext(struct pt_regs *regs, struct sigcontext __user *sc)
 	if (used_math) {
 		/* restore fpu context if we have used it before */
 		if (!err)
-			err = check_and_restore_fp_context(sc);
+			err = check_and_restore_fp_context(sc, used_math);
 	} else {
-		/* signal handler may have used FPU.  Give it up. */
+		/* signal handler may have used FPU or MSA. Disable them. */
+		disable_msa();
 		lose_fpu(0);
 	}