From 0d6f8b604701fc55a03d51bab8b96d718469c975 Mon Sep 17 00:00:00 2001
From: Daria Sukhonina <dariasukhonina@gmail.com>
Date: Wed, 13 Jul 2022 15:35:10 +0300
Subject: [PATCH] feat: mark `psp::math` functions as safe

This is possible due to 9546fa1d2cd6551dbc6aff40852f6b8f6a8f68ba, which initializes a vfpu enabled thread inside of the `module_start`. It is unsafe to reach vfpu disabled execution context.
---
 psp/src/math/mod.rs | 136 +++++++++++++++++++++++---------------------
 1 file changed, 72 insertions(+), 64 deletions(-)

diff --git a/psp/src/math/mod.rs b/psp/src/math/mod.rs
index f6c78248..151a64b0 100644
--- a/psp/src/math/mod.rs
+++ b/psp/src/math/mod.rs
@@ -1,5 +1,5 @@
 #[no_mangle]
-pub unsafe extern "C" fn fminf(x: f32, y: f32) -> f32 {
+pub extern "C" fn fminf(x: f32, y: f32) -> f32 {
     let out: f32;
     if x.is_nan() && !y.is_nan() {
         out = y;
@@ -8,28 +8,30 @@ pub unsafe extern "C" fn fminf(x: f32, y: f32) -> f32 {
     } else if x.is_nan() && y.is_nan() {
         out = core::f32::NAN;
     } else {
-        vfpu_asm! (
-            "mfc1 {tmp1}, {x}",
-            "mfc1 {tmp2}, {y}",
-            "mtv {tmp1}, S000",
-            "mtv {tmp2}, S001",
-            "vmin.s S000, S000, S001",
-            "mfv {tmp1}, S000",
-            "mtc1 {tmp1}, {out}",
-            "nop",
-            x = in(freg) x,
-            y = in(freg) y,
-            tmp1 = out(reg) _,
-            tmp2 = out(reg) _,
-            out = out(freg) out,
-            options(nostack, nomem),
-        );
+        unsafe {
+            vfpu_asm! (
+                "mfc1 {tmp1}, {x}",
+                "mfc1 {tmp2}, {y}",
+                "mtv {tmp1}, S000",
+                "mtv {tmp2}, S001",
+                "vmin.s S000, S000, S001",
+                "mfv {tmp1}, S000",
+                "mtc1 {tmp1}, {out}",
+                "nop",
+                x = in(freg) x,
+                y = in(freg) y,
+                tmp1 = out(reg) _,
+                tmp2 = out(reg) _,
+                out = out(freg) out,
+                options(nostack, nomem),
+            );
+        }
     }
     out
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn fmaxf(x: f32, y: f32) -> f32 {
+pub extern "C" fn fmaxf(x: f32, y: f32) -> f32 {
     let out: f32;
     if x.is_nan() && !y.is_nan() {
         out = y;
@@ -38,63 +40,69 @@ pub unsafe extern "C" fn fmaxf(x: f32, y: f32) -> f32 {
     } else if x.is_nan() && y.is_nan() {
         out = core::f32::NAN;
     } else {
-        vfpu_asm! (
-            "mfc1 {tmp1}, {x}",
-            "mfc1 {tmp2}, {y}",
-            "mtv {tmp1}, S000",
-            "mtv {tmp2}, S001",
-            "vmax.s S000, S000, S001",
-            "mfv {tmp1}, S000",
-            "mtc1 {tmp1}, {out}",
-            "nop",
-            x = in(freg) x,
-            y = in(freg) y,
-            tmp1 = out(reg) _,
-            tmp2 = out(reg) _,
-            out = out(freg) out,
-            options(nostack, nomem),
-        );
+        unsafe {
+            vfpu_asm! (
+                "mfc1 {tmp1}, {x}",
+                "mfc1 {tmp2}, {y}",
+                "mtv {tmp1}, S000",
+                "mtv {tmp2}, S001",
+                "vmax.s S000, S000, S001",
+                "mfv {tmp1}, S000",
+                "mtc1 {tmp1}, {out}",
+                "nop",
+                x = in(freg) x,
+                y = in(freg) y,
+                tmp1 = out(reg) _,
+                tmp2 = out(reg) _,
+                out = out(freg) out,
+                options(nostack, nomem),
+            );
+        }
     }
     out
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn cosf(scalar: f32) -> f32 {
+pub extern "C" fn cosf(scalar: f32) -> f32 {
     let out: f32;
-    vfpu_asm! (
-        "mfc1 {tmp}, {scalar}",
-        "mtv {tmp}, S000",
-        "nop",
-        "vcst.s S001, VFPU_2_PI",
-        "vmul.s S000, S000, S001",
-        "vcos.s S000, S000",
-        "mfv {tmp}, S000",
-        "mtc1 {tmp}, {scalar}",
-        "nop",
-        scalar = inlateout(freg) scalar => out,
-        tmp = out(reg) _,
-        options(nostack, nomem),
-    );
+    unsafe {
+        vfpu_asm! (
+            "mfc1 {tmp}, {scalar}",
+            "mtv {tmp}, S000",
+            "nop",
+            "vcst.s S001, VFPU_2_PI",
+            "vmul.s S000, S000, S001",
+            "vcos.s S000, S000",
+            "mfv {tmp}, S000",
+            "mtc1 {tmp}, {scalar}",
+            "nop",
+            scalar = inlateout(freg) scalar => out,
+            tmp = out(reg) _,
+            options(nostack, nomem),
+        );
+    }
     out
 }
 
 #[no_mangle]
-pub unsafe extern "C" fn sinf(scalar: f32) -> f32 {
+pub extern "C" fn sinf(scalar: f32) -> f32 {
     let out: f32;
-    vfpu_asm! (
-        "mfc1 {tmp}, {scalar}",
-        "mtv {tmp}, S000",
-        "nop",
-        "vcst.s S001, VFPU_2_PI",
-        "vmul.s S000, S000, S001",
-        "vsin.s S000, S000",
-        "mfv {tmp}, S000",
-        "mtc1 {tmp}, {scalar}",
-        "nop",
-        scalar = inlateout(freg) scalar => out,
-        tmp = out(reg) _,
-        options(nostack, nomem),
-    );
+    unsafe {
+        vfpu_asm! (
+            "mfc1 {tmp}, {scalar}",
+            "mtv {tmp}, S000",
+            "nop",
+            "vcst.s S001, VFPU_2_PI",
+            "vmul.s S000, S000, S001",
+            "vsin.s S000, S000",
+            "mfv {tmp}, S000",
+            "mtc1 {tmp}, {scalar}",
+            "nop",
+            scalar = inlateout(freg) scalar => out,
+            tmp = out(reg) _,
+            options(nostack, nomem),
+        );
+    }
     out
 }
 // borrowed from https://github.com/samcrow/cmsis_dsp.rs/blob/master/src/libm_c.rs