439f566f3f
This moves them into a new `wasmtime-asm-macros` crate that can be used not just from the `wasmtime-fibers` crate but also from other crates (e.g. we will need them in https://github.com/bytecodealliance/wasmtime/pull/4431).
86 lines
2.6 KiB
Rust
86 lines
2.6 KiB
Rust
// A WORD OF CAUTION
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//
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// This entire file basically needs to be kept in sync with itself. It's not
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// really possible to modify just one bit of this file without understanding
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// all the other bits. Documentation tries to reference various bits here and
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// there but try to make sure to read over everything before tweaking things!
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//
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// Also at this time this file is heavily based off the x86_64 file, so you'll
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// probably want to read that one as well.
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use wasmtime_asm_macros::{asm_func, asm_sym};
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// fn(top_of_stack(%r0): *mut u8)
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asm_func!(
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"wasmtime_fiber_switch",
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"
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// Save callee-saved registers
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push {{r4-r11,lr}}
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// Swap stacks, recording our current stack pointer
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ldr r4, [r0, #-0x08]
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str sp, [r0, #-0x08]
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mov sp, r4
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// Restore and return
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pop {{r4-r11,lr}}
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bx lr
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",
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);
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// fn(
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// top_of_stack(%r0): *mut u8,
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// entry_point(%r1): extern fn(*mut u8, *mut u8),
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// entry_arg0(%r2): *mut u8,
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// )
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asm_func!(
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"wasmtime_fiber_init",
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"
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adr r3, wasmtime_fiber_start
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str r3, [r0, #-0x0c] // => lr
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str r0, [r0, #-0x10] // => r11
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str r1, [r0, #-0x14] // => r10
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str r2, [r0, #-0x18] // => r9
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add r3, r0, #-0x2c
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str r3, [r0, #-0x08]
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bx lr
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",
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);
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asm_func!(
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"wasmtime_fiber_start",
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"
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.cfi_startproc simple
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.cfi_def_cfa_offset 0
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// See the x86_64 file for more commentary on what these CFI directives
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// are doing. Like over there note that the relative offsets to
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// registers here match the frame layout in `wasmtime_fiber_switch`.
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//
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// TODO: this is only lightly tested. This gets backtraces in gdb but
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// not at runtime. Perhaps the libgcc at runtime was too old? Doesn't
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// support something here? Unclear. Will need investigation if someone
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// ends up needing this and it still doesn't work.
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.cfi_escape 0x0f, /* DW_CFA_def_cfa_expression */ \
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5, /* the byte length of this expression */ \
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0x7d, 0x00, /* DW_OP_breg14(%sp) + 0 */ \
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0x06, /* DW_OP_deref */ \
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0x23, 0x24 /* DW_OP_plus_uconst 0x24 */
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.cfi_rel_offset lr, -0x04
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.cfi_rel_offset r11, -0x08
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.cfi_rel_offset r10, -0x0c
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.cfi_rel_offset r9, -0x10
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.cfi_rel_offset r8, -0x14
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.cfi_rel_offset r7, -0x18
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.cfi_rel_offset r6, -0x1c
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.cfi_rel_offset r5, -0x20
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.cfi_rel_offset r4, -0x24
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mov r1, r11
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mov r0, r9
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blx r10
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.cfi_endproc
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",
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);
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