123 lines
4.0 KiB
ArmAsm
123 lines
4.0 KiB
ArmAsm
// 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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#include "header.h"
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// fn(top_of_stack(%x0): *mut u8)
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HIDDEN(wasmtime_fiber_switch)
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GLOBL(wasmtime_fiber_switch)
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.p2align 2
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TYPE(wasmtime_fiber_switch)
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FUNCTION(wasmtime_fiber_switch):
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// Save all callee-saved registers on the stack since we're assuming
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// they're clobbered as a result of the stack switch.
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stp lr, fp, [sp, -16]!
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stp x20, x19, [sp, -16]!
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stp x22, x21, [sp, -16]!
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stp x24, x23, [sp, -16]!
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stp x26, x25, [sp, -16]!
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stp x28, x27, [sp, -16]!
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stp d9, d8, [sp, -16]!
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stp d11, d10, [sp, -16]!
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stp d13, d12, [sp, -16]!
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stp d15, d14, [sp, -16]!
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// Load our previously saved stack pointer to resume to, and save off our
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// current stack pointer on where to come back to eventually.
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ldr x8, [x0, -0x10]
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mov x9, sp
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str x9, [x0, -0x10]
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// Switch to the new stack and restore all our callee-saved registers after
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// the switch and return to our new stack.
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mov sp, x8
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ldp d15, d14, [sp], 16
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ldp d13, d12, [sp], 16
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ldp d11, d10, [sp], 16
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ldp d9, d8, [sp], 16
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ldp x28, x27, [sp], 16
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ldp x26, x25, [sp], 16
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ldp x24, x23, [sp], 16
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ldp x22, x21, [sp], 16
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ldp x20, x19, [sp], 16
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ldp lr, fp, [sp], 16
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ret
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SIZE(wasmtime_fiber_switch)
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// fn(
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// top_of_stack(%x0): *mut u8,
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// entry_point(%x1): extern fn(*mut u8, *mut u8),
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// entry_arg0(%x2): *mut u8,
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// )
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HIDDEN(wasmtime_fiber_init)
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GLOBL(wasmtime_fiber_init)
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.p2align 2
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TYPE(wasmtime_fiber_init)
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FUNCTION(wasmtime_fiber_init):
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adr x8, FUNCTION(wasmtime_fiber_start)
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stp x0, x8, [x0, -0x28] // x0 => x19, x8 => lr
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stp x2, x1, [x0, -0x38] // x1 => x20, x2 => x21
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// `wasmtime_fiber_switch` has an 0xa0 byte stack, and we add 0x10 more for
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// the original reserved 16 bytes.
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add x8, x0, -0xb0
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str x8, [x0, -0x10]
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ret
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SIZE(wasmtime_fiber_init)
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.p2align 2
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TYPE(wasmtime_fiber_start)
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FUNCTION(wasmtime_fiber_start):
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.cfi_startproc simple
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// See the x86_64 file for more commentary on what these CFI directives are
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// doing. Like over there note that the relative offsets to registers here
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// match the frame layout in `wasmtime_fiber_switch`.
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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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0x6f, /* DW_OP_reg31(%sp) */ \
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0x06, /* DW_OP_deref */ \
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0x23, 0xa0, 0x1 /* DW_OP_plus_uconst 0xa0 */
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.cfi_rel_offset x29, -0x08
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.cfi_rel_offset lr, -0x10
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.cfi_rel_offset x19, -0x18
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.cfi_rel_offset x20, -0x20
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.cfi_rel_offset x21, -0x28
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.cfi_rel_offset x22, -0x30
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.cfi_rel_offset x23, -0x38
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.cfi_rel_offset x24, -0x40
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.cfi_rel_offset x25, -0x48
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.cfi_rel_offset x26, -0x50
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.cfi_rel_offset x27, -0x58
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// Load our two arguments from the stack, where x1 is our start procedure
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// and x0 is its first argument. This also blows away the stack space used
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// by those two arguments.
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mov x0, x21
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mov x1, x19
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// ... and then we call the function! Note that this is a function call so
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// our frame stays on the stack to backtrace through.
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blr x20
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// Unreachable, here for safety. This should help catch unexpected behaviors.
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// Use a noticeable payload so one can grep for it in the codebase.
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brk 0xf1b3
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.cfi_endproc
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SIZE(wasmtime_fiber_start)
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// This omits the `.subsections_via_symbols` directive on macOS which means we
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// can't GC specific intrinsics from this file, but it enables usage of the
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// `adr` instruction above in lieu of figuring out a slightly more complicated
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// way of implementing that.
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#ifndef CFG_TARGET_OS_macos
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FOOTER
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#endif
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