[PATCH v4 04/14] arm64/signal: Add FPMR signal handling

[Mark Brown]

Expose FPMR in the signal context on systems where it is supported. The
kernel validates the exact size of the FPSIMD registers so we can't readily
add it to fpsimd_context without disruption.

Signed-off-by: Mark Brown <broonie at kernel.org>
---
 arch/arm64/include/uapi/asm/sigcontext.h |  8 +++++
 arch/arm64/kernel/signal.c               | 59 ++++++++++++++++++++++++++++++++
 2 files changed, 67 insertions(+)

diff --git a/arch/arm64/include/uapi/asm/sigcontext.h b/arch/arm64/include/uapi/asm/sigcontext.h
index f23c1dc3f002..8a45b7a411e0 100644
--- a/arch/arm64/include/uapi/asm/sigcontext.h
+++ b/arch/arm64/include/uapi/asm/sigcontext.h
@@ -152,6 +152,14 @@ struct tpidr2_context {
 	__u64 tpidr2;
 };
 
+/* FPMR context */
+#define FPMR_MAGIC	0x46504d52
+
+struct fpmr_context {
+	struct _aarch64_ctx head;
+	__u64 fpmr;
+};
+
 #define ZA_MAGIC	0x54366345
 
 struct za_context {
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index 0e8beb3349ea..460823baa603 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -60,6 +60,7 @@ struct rt_sigframe_user_layout {
 	unsigned long tpidr2_offset;
 	unsigned long za_offset;
 	unsigned long zt_offset;
+	unsigned long fpmr_offset;
 	unsigned long extra_offset;
 	unsigned long end_offset;
 };
@@ -182,6 +183,8 @@ struct user_ctxs {
 	u32 za_size;
 	struct zt_context __user *zt;
 	u32 zt_size;
+	struct fpmr_context __user *fpmr;
+	u32 fpmr_size;
 };
 
 static int preserve_fpsimd_context(struct fpsimd_context __user *ctx)
@@ -227,6 +230,33 @@ static int restore_fpsimd_context(struct user_ctxs *user)
 	return err ? -EFAULT : 0;
 }
 
+static int preserve_fpmr_context(struct fpmr_context __user *ctx)
+{
+	int err = 0;
+
+	current->thread.uw.fpmr = read_sysreg_s(SYS_FPMR);
+
+	__put_user_error(FPMR_MAGIC, &ctx->head.magic, err);
+	__put_user_error(sizeof(*ctx), &ctx->head.size, err);
+	__put_user_error(current->thread.uw.fpmr, &ctx->fpmr, err);
+
+	return err;
+}
+
+static int restore_fpmr_context(struct user_ctxs *user)
+{
+	u64 fpmr;
+	int err = 0;
+
+	if (user->fpmr_size != sizeof(*user->fpmr))
+		return -EINVAL;
+
+	__get_user_error(fpmr, &user->fpmr->fpmr, err);
+	if (!err)
+		write_sysreg_s(fpmr, SYS_FPMR);
+
+	return err;
+}
 
 #ifdef CONFIG_ARM64_SVE
 
@@ -590,6 +620,7 @@ static int parse_user_sigframe(struct user_ctxs *user,
 	user->tpidr2 = NULL;
 	user->za = NULL;
 	user->zt = NULL;
+	user->fpmr = NULL;
 
 	if (!IS_ALIGNED((unsigned long)base, 16))
 		goto invalid;
@@ -684,6 +715,17 @@ static int parse_user_sigframe(struct user_ctxs *user,
 			user->zt_size = size;
 			break;
 
+		case FPMR_MAGIC:
+			if (!system_supports_fpmr())
+				goto invalid;
+
+			if (user->fpmr)
+				goto invalid;
+
+			user->fpmr = (struct fpmr_context __user *)head;
+			user->fpmr_size = size;
+			break;
+
 		case EXTRA_MAGIC:
 			if (have_extra_context)
 				goto invalid;
@@ -806,6 +848,9 @@ static int restore_sigframe(struct pt_regs *regs,
 	if (err == 0 && system_supports_tpidr2() && user.tpidr2)
 		err = restore_tpidr2_context(&user);
 
+	if (err == 0 && system_supports_fpmr() && user.fpmr)
+		err = restore_fpmr_context(&user);
+
 	if (err == 0 && system_supports_sme() && user.za)
 		err = restore_za_context(&user);
 
@@ -928,6 +973,13 @@ static int setup_sigframe_layout(struct rt_sigframe_user_layout *user,
 		}
 	}
 
+	if (system_supports_fpmr()) {
+		err = sigframe_alloc(user, &user->fpmr_offset,
+				     sizeof(struct fpmr_context));
+		if (err)
+			return err;
+	}
+
 	return sigframe_alloc_end(user);
 }
 
@@ -983,6 +1035,13 @@ static int setup_sigframe(struct rt_sigframe_user_layout *user,
 		err |= preserve_tpidr2_context(tpidr2_ctx);
 	}
 
+	/* FPMR if supported */
+	if (system_supports_fpmr() && err == 0) {
+		struct fpmr_context __user *fpmr_ctx =
+			apply_user_offset(user, user->fpmr_offset);
+		err |= preserve_fpmr_context(fpmr_ctx);
+	}
+
 	/* ZA state if present */
 	if (system_supports_sme() && err == 0 && user->za_offset) {
 		struct za_context __user *za_ctx =

-- 
2.30.2