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context (x86_64): change arch_context_saveandcall behaviour

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Matheus
2023-06-25 15:41:24 -03:00
parent 2ae3846b17
commit f03c34075e
1 changed files with 9 additions and 6 deletions
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kernel-src/arch/x86-64/context.asm
+9 -6
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@@ -36,15 +36,18 @@ arch_context_switch:
; saves context on the stack and passes as the argument to a function ; saves context on the stack and passes as the argument to a function
; since this uses the C system V abi, some registers can be clobbered (in this case, r10 and r11) ; since this uses the C system V abi, some registers can be clobbered (in this case, r10 and r11)
; rdi has the pointer to the function to call ; rdi has the pointer to the function to call
; rsi has the pointer to the stack the function should have on call ; rsi has the pointer to the stack the function should have on call. if NULL the stack is not changed
; if the main function returns, just return normally ; if the main function returns, do a context switch as the registers could have been changed
global arch_context_saveandcall global arch_context_saveandcall
arch_context_saveandcall: arch_context_saveandcall:
mov r11, [rsp] ; save return address on scratch register mov r11, [rsp] ; save return address on scratch register
mov r10, rsp mov r10, rsp
add r10, 8 ; stack pointer before the call instruction add r10, 8 ; stack pointer before the call instruction
test rsi,rsi
jz .nostackchange
mov rsp, rsi ; use desired stack mov rsp, rsi ; use desired stack
.nostackchange:
push qword 0x10 ; SS push qword 0x10 ; SS
push r10 ; RSP push r10 ; RSP
pushf ; movs and pushes don't affect flags pushf ; movs and pushes don't affect flags
@@ -75,9 +78,9 @@ arch_context_saveandcall:
mov r11, rdi ; save function to call mov r11, rdi ; save function to call
mov rdi, rsp ; first argument is the context struct mov rdi, rsp ; first argument is the context struct
push r10 ; save old stack
call r11 ; jump to the desired function call r11 ; jump to the desired function
pop rsp ; restore old stack ; do context switch to return
sub rsp, 8 cli
ret mov rdi, rsp
call arch_context_switch