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k4sh
Cheater
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Joined: 01 Mar 2016
Posts: 28
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 Posted: Wed Mar 30, 2016 3:54 pm Post subject: How to 16 byte align rsp |
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I need to call a lua function in a code injected.
The call CE lua function template says that rsp has to be 16 byte aligned prior to call my function.
Here is a portion of my actual code :
| Code: |
...
mov rcx, setnewxyratios
sub rsp,20
call LuaFunctionCall
add rsp,20
...
...
setnewxyratios:
db 'setNewXYRatios',0
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The only ending is a game crash after LuaFunctionCall has been called. |
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mgr.inz.Player
I post too much
 Reputation: 222
Joined: 07 Nov 2008
Posts: 4438
Location: W kraju nad Wisla. UTC+01:00
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| Posted: Wed Mar 30, 2016 4:12 pm Post subject: |
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| Code: | push rbp
mov rbp,rsp
sub rsp,20
and rsp,-10 // aligning the stack with the next lowest 16-byte boundary
mov rcx, setnewxyratios
call LuaFunctionCall
mov rsp,rbp
pop rbp
...
...
setnewxyratios:
db 'setNewXYRatios',0 |
and rsp,-10 instruction zeroes the low 4 bits of rsp, which may decrease it (it might reserve an additional 8 bytes if needed)
_________________
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k4sh
Cheater
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Joined: 01 Mar 2016
Posts: 28
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| Posted: Fri Apr 01, 2016 12:14 pm Post subject: |
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Again big thank mgr.inz.Player
Now with this code, my game is not crashing anymore :
| Code: |
...
{$lua}
function test()
print('triggered')
end
{$asm}
...
mov rcx,[rax+rdi*8] <== original game code
mov rax,[rcx] <== original game code
push rcx
push rax
push rbp
mov rbp,rsp
sub rsp,20
and rsp,-10 // aligning the stack with the next lowest 16-byte boundary
mov rcx, setnewxyratios
call LuaFunctionCall
mov rsp,rbp
pop rbp
pop rax
pop rcx
...
setnewxyratios:
db 'test',0
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However, my function test to print the string triggered is never executed as i don't get any lua output.
What could i have done wrong ? |
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