fix: unrecognized instruction mnemonic on riscv target

ref: rust-lang/rust#134960

Author: zjp-CN

src/arch/riscv.rs

@@ -61,36 +61,9 @@ impl TaskContext {
 }
 
 #[cfg(target_arch = "riscv32")]
-core::arch::global_asm!(
-    r"
-.ifndef XLENB
-.equ XLENB, 4
-
-.macro LDR rd, rs, off
-    lw \rd, \off*XLENB(\rs)
-.endm
-.macro STR rs2, rs1, off
-    sw \rs2, \off*XLENB(\rs1)
-.endm
-
-.endif"
-);
-
+const XLENB: usize = 4;
 #[cfg(target_arch = "riscv64")]
-core::arch::global_asm!(
-    r"
-.ifndef XLENB
-.equ XLENB, 8
-
-.macro LDR rd, rs, off
-    ld \rd, \off*XLENB(\rs)
-.endm
-.macro STR rs2, rs1, off
-    sd \rs2, \off*XLENB(\rs1)
-.endm
-
-.endif",
-);
+const XLENB: usize = 8;
 
 #[naked]
 /// Switches the context from the current task to the next task.
@@ -101,40 +74,52 @@ core::arch::global_asm!(
 pub unsafe extern "C" fn context_switch(_current_task: &mut TaskContext, _next_task: &TaskContext) {
     unsafe {
         naked_asm!(
-            "
-        // save old context (callee-saved registers)
-        STR     ra, a0, 0
-        STR     sp, a0, 1
-        STR     s0, a0, 2
-        STR     s1, a0, 3
-        STR     s2, a0, 4
-        STR     s3, a0, 5
-        STR     s4, a0, 6
-        STR     s5, a0, 7
-        STR     s6, a0, 8
-        STR     s7, a0, 9
-        STR     s8, a0, 10
-        STR     s9, a0, 11
-        STR     s10, a0, 12
-        STR     s11, a0, 13
-
-        // restore new context
-        LDR     s11, a1, 13
-        LDR     s10, a1, 12
-        LDR     s9, a1, 11
-        LDR     s8, a1, 10
-        LDR     s7, a1, 9
-        LDR     s6, a1, 8
-        LDR     s5, a1, 7
-        LDR     s4, a1, 6
-        LDR     s3, a1, 5
-        LDR     s2, a1, 4
-        LDR     s1, a1, 3
-        LDR     s0, a1, 2
-        LDR     sp, a1, 1
-        LDR     ra, a1, 0
-
-        ret",
+            r"
+            .ifndef XLENB
+            .equ XLENB, {XLENB}
+
+            .macro LDR rd, rs, off
+                ld \rd, \off*XLENB(\rs)
+            .endm
+            .macro STR rs2, rs1, off
+                sd \rs2, \off*XLENB(\rs1)
+            .endm
+            .endif
+
+            // save old context (callee-saved registers)
+            STR     ra, a0, 0
+            STR     sp, a0, 1
+            STR     s0, a0, 2
+            STR     s1, a0, 3
+            STR     s2, a0, 4
+            STR     s3, a0, 5
+            STR     s4, a0, 6
+            STR     s5, a0, 7
+            STR     s6, a0, 8
+            STR     s7, a0, 9
+            STR     s8, a0, 10
+            STR     s9, a0, 11
+            STR     s10, a0, 12
+            STR     s11, a0, 13
+
+            // restore new context
+            LDR     s11, a1, 13
+            LDR     s10, a1, 12
+            LDR     s9, a1, 11
+            LDR     s8, a1, 10
+            LDR     s7, a1, 9
+            LDR     s6, a1, 8
+            LDR     s5, a1, 7
+            LDR     s4, a1, 6
+            LDR     s3, a1, 5
+            LDR     s2, a1, 4
+            LDR     s1, a1, 3
+            LDR     s0, a1, 2
+            LDR     sp, a1, 1
+            LDR     ra, a1, 0
+
+            ret",
+            XLENB = const XLENB
         )
     }
 }