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setup.S: Fix guest/host stack switching

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This commit is contained in:
Luke Street
2025-11-11 21:25:40 -07:00
parent f012b22101
commit 3b89db146b
1 changed files with 5 additions and 4 deletions
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9
src/setup.S
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@@ -12,14 +12,13 @@
# Installs ds/es selectors in 32-bit mode
ASM_GLOBAL(installSelectors, @function)
mov r8, rsp # save host stack
mov rdx, qword ptr [rdi+TEB_SP] # fetch guest stack
mov rsp, qword ptr [rdi+TEB_SP] # switch to guest stack
mov ax, cs # fetch host code segment selector
mov word ptr [rdi+TEB_HOST_CS_SEL], ax # store host code segment selector
mov ax, word ptr [rdi+TEB_DS_SEL] # user data segment selector
LJMP32 rdi # far jump into 32-bit code
mov ds, ax # setup data segment
mov es, ax # setup extra segment
mov esp, edx # switch to guest stack
LJMP64 edi # far jump into 64-bit code
mov rsp, r8 # switch to host stack
ret
@@ -30,9 +29,8 @@ ASM_END(installSelectors)
ASM_GLOBAL(setThreadArea64, @function)
push rbx # save rbx
mov r8, rsp # save host stack
mov rdx, qword ptr [rsi+TEB_SP] # fetch guest stack
mov rsp, qword ptr [rsi+TEB_SP] # switch to guest stack
LJMP32 rsi # far jump into 32-bit code
mov esp, edx # switch to guest stack
sub esp, 0x10 # sizeof(user_desc)
mov dword ptr [esp], edi # entry_number (arg 0)
mov dword ptr [esp+4], esi # base_addr (arg 1)
@@ -59,6 +57,8 @@ ASM_END(setThreadArea64)
# bool installSelectors(TEB *teb)
ASM_GLOBAL(installSelectors, @function)
mov r8, rsp # save host stack
mov rsp, qword ptr [rsi+TEB_SP] # fetch guest stack
mov ax, cs # fetch host code segment selector
mov word ptr [rdi+TEB_HOST_CS_SEL], ax # store host code segment selector
mov ax, word ptr [rdi+TEB_DS_SEL] # fetch data segment selector
@@ -68,6 +68,7 @@ ASM_GLOBAL(installSelectors, @function)
mov es, ax # setup extra segment
mov fs, dx # setup fs segment
LJMP64 edi # far jump into 64-bit code
mov rsp, r8 # switch to host stack
mov rax, 1 # return true
ret
ASM_END(installSelectors)