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BITS 64
default rel
extern zest_cfi_dispatch_c
%define cfi_dispatch_translation_cache_entries 16*1024
section .tls alloc write align=8 tls
global translation_cache_src
translation_cache_src: times cfi_dispatch_translation_cache_entries dq 0
translation_cache_targ: times cfi_dispatch_translation_cache_entries dq 0
section .text
global zest_cfi_dispatch:function
zest_cfi_dispatch:
; not saving rbx, rsp, rbp, r12-r15 as C code should save them.
lea rsp, [rsp-128]
pushf
push rax
push rcx
; check translation cache.
mov rax,[rel translation_cache_src wrt ..gottpoff]
; rax contains tls address of translation_cache_src
; hash target
mov rcx, r11
and rcx, ((cfi_dispatch_translation_cache_entries) -1)
cmp r11, [fs:rax+rcx*8]
jne enter_c_code
allow_xfer_fast:
mov rax, [fs:rax+rcx*8+cfi_dispatch_translation_cache_entries*8]
; decide if we need to check the transfer, or if it's allowed.
; checking the xfer is done if the target module has a zest_cfi symbol.
; rax contains the address, if the symbol exists.
; rax is 0 if the symbol does not exist.
cmp rax, 0
je allow_xfer
check_xfer:
mov rcx, rax ; save zest_cfi address into rcx.
mov rax, [rsp+8] ; restore rax.
mov [rsp+8], rcx ; write zest_cfi over rax location.
pop rcx ; restore rcx.
lea rsp, [rsp+8] ; skip over stack space for saved rax, which is now used for zest_zfi address.
popf ; restore rest of state.
lea rsp, [rsp+128] ; undo read zone
jmp [rsp-128-8-8] ; jump to zest_cfi address stored on stack. -128 for red zone, -8 for flags, -8 for rax.
allow_xfer:
pop rcx
pop rax
popf
lea rsp, [rsp+128]
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enter_c_code:
push rdx
push rsi
push rdi
push r8
push r9
push r10
push r11
mov rdi, r11 ; r11 is the cfi reg for x86-64, copy it to rdi for C-calling convention.
call zest_cfi_dispatch_c wrt ..plt
; rax has the address of zest_cfi in the target module.
pop r11
pop r10
pop r9
pop r8
pop rdi
pop rsi
pop rdx
; rax contains tls address of translation_cache_src
; hash target
mov rcx, r11
and rcx, ((cfi_dispatch_translation_cache_entries) -1)
lea rcx, [rcx*8]
add rcx, [rel translation_cache_src wrt ..gottpoff]
mov [fs:rcx], r11
mov [fs:rcx+cfi_dispatch_translation_cache_entries*8], rax
; resume computation
jmp decide_to_check