1 // A WORD OF CAUTION 2 // 3 // This entire file basically needs to be kept in sync with itself. It's not 4 // really possible to modify just one bit of this file without understanding 5 // all the other bits. Documentation tries to reference various bits here and 6 // there but try to make sure to read over everything before tweaking things! 7 8 use core::arch::naked_asm; 9 10 #[unsafe(naked)] 11 pub(crate) unsafe extern "C" fn wasmtime_fiber_switch(top_of_stack: *mut u8 /* a0 */) { 12 naked_asm!( 13 " 14 // See https://github.com/rust-lang/rust/issues/80608. 15 .attribute arch, \"rv64gc\" 16 17 // We're switching to arbitrary code somewhere else, so pessimistically 18 // assume that all callee-save register are clobbered. This means we need 19 // to save/restore all of them. 20 // 21 // Note that this order for saving is important since we use CFI directives 22 // below to point to where all the saved registers are. 23 sd ra,-0x8(sp) 24 sd fp,-0x10(sp) 25 sd s1,-0x18(sp) 26 sd s2,-0x20(sp) 27 sd s3,-0x28(sp) 28 sd s4,-0x30(sp) 29 sd s5,-0x38(sp) 30 sd s6,-0x40(sp) 31 sd s7,-0x48(sp) 32 sd s8,-0x50(sp) 33 sd s9,-0x58(sp) 34 sd s10,-0x60(sp) 35 sd s11,-0x68(sp) 36 fsd fs0,-0x70(sp) 37 fsd fs1,-0x78(sp) 38 fsd fs2,-0x80(sp) 39 fsd fs3,-0x88(sp) 40 fsd fs4,-0x90(sp) 41 fsd fs5,-0x98(sp) 42 fsd fs6,-0xa0(sp) 43 fsd fs7,-0xa8(sp) 44 fsd fs8,-0xb0(sp) 45 fsd fs9,-0xb8(sp) 46 fsd fs10,-0xc0(sp) 47 fsd fs11,-0xc8(sp) 48 addi sp , sp , -0xd0 49 50 ld t0 ,-0x10(a0) 51 sd sp ,-0x10(a0) 52 53 // Swap stacks and restore all our callee-saved registers 54 mv sp,t0 55 56 fld fs11,0x8(sp) 57 fld fs10,0x10(sp) 58 fld fs9,0x18(sp) 59 fld fs8,0x20(sp) 60 fld fs7,0x28(sp) 61 fld fs6,0x30(sp) 62 fld fs5,0x38(sp) 63 fld fs4,0x40(sp) 64 fld fs3,0x48(sp) 65 fld fs2,0x50(sp) 66 fld fs1,0x58(sp) 67 fld fs0,0x60(sp) 68 ld s11,0x68(sp) 69 ld s10,0x70(sp) 70 ld s9,0x78(sp) 71 ld s8,0x80(sp) 72 ld s7,0x88(sp) 73 ld s6,0x90(sp) 74 ld s5,0x98(sp) 75 ld s4,0xa0(sp) 76 ld s3,0xa8(sp) 77 ld s2,0xb0(sp) 78 ld s1,0xb8(sp) 79 ld fp,0xc0(sp) 80 ld ra,0xc8(sp) 81 addi sp , sp , 0xd0 82 jr ra 83 ", 84 ); 85 } 86 87 pub(crate) unsafe fn wasmtime_fiber_init( 88 top_of_stack: *mut u8, 89 entry_point: extern "C" fn(*mut u8, *mut u8), 90 entry_arg0: *mut u8, 91 ) { 92 #[repr(C)] 93 #[derive(Default)] 94 struct InitialStack { 95 align_to_16_byte_size: u64, 96 97 fs: [f64; 12], 98 99 s11: *mut u8, 100 s10: *mut u8, 101 s9: *mut u8, 102 s8: *mut u8, 103 s7: *mut u8, 104 s6: *mut u8, 105 s5: *mut u8, 106 s4: *mut u8, 107 s3: *mut u8, 108 s2: *mut u8, 109 s1: *mut u8, 110 fp: *mut u8, 111 112 ra: *mut u8, 113 114 // unix.rs reserved space 115 last_sp: *mut u8, 116 run_result: *mut u8, 117 } 118 119 unsafe { 120 let initial_stack = top_of_stack.cast::<InitialStack>().sub(1); 121 initial_stack.write(InitialStack { 122 s1: entry_point as *mut u8, 123 s2: entry_arg0, 124 fp: top_of_stack, 125 ra: wasmtime_fiber_start as *mut u8, 126 last_sp: initial_stack.cast(), 127 ..InitialStack::default() 128 }); 129 } 130 } 131 132 #[unsafe(naked)] 133 unsafe extern "C" fn wasmtime_fiber_start() -> ! { 134 naked_asm!( 135 " 136 .cfi_startproc simple 137 .cfi_def_cfa_offset 0 138 139 140 .cfi_escape 0x0f, /* DW_CFA_def_cfa_expression */ \ 141 5, /* the byte length of this expression */ \ 142 0x52, /* DW_OP_reg2 (sp) */ \ 143 0x06, /* DW_OP_deref */ \ 144 0x08, 0xd0 , /* DW_OP_const1u 0xc8 */ \ 145 0x22 /* DW_OP_plus */ 146 147 148 .cfi_rel_offset ra,-0x8 149 .cfi_rel_offset fp,-0x10 150 .cfi_rel_offset s1,-0x18 151 .cfi_rel_offset s2,-0x20 152 .cfi_rel_offset s3,-0x28 153 .cfi_rel_offset s4,-0x30 154 .cfi_rel_offset s5,-0x38 155 .cfi_rel_offset s6,-0x40 156 .cfi_rel_offset s7,-0x48 157 .cfi_rel_offset s8,-0x50 158 .cfi_rel_offset s9,-0x58 159 .cfi_rel_offset s10,-0x60 160 .cfi_rel_offset s11,-0x68 161 .cfi_rel_offset fs0,-0x70 162 .cfi_rel_offset fs1,-0x78 163 .cfi_rel_offset fs2,-0x80 164 .cfi_rel_offset fs3,-0x88 165 .cfi_rel_offset fs4,-0x90 166 .cfi_rel_offset fs5,-0x98 167 .cfi_rel_offset fs6,-0xa0 168 .cfi_rel_offset fs7,-0xa8 169 .cfi_rel_offset fs8,-0xb0 170 .cfi_rel_offset fs9,-0xb8 171 .cfi_rel_offset fs10,-0xc0 172 .cfi_rel_offset fs11,-0xc8 173 174 mv a0,s2 175 mv a1,fp 176 jalr s1 177 // .4byte 0 will cause panic. 178 // for safety just like x86_64.rs. 179 .4byte 0 180 .cfi_endproc 181 ", 182 ); 183 } 184