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[kernel] Save ring3 rflags in cpu_data, not just stack

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So that kernel code can modify user rflags, save it in the CPU state
data, and save that off to the TCB when switching tasks.
This commit is contained in:
Justin C. Miller
2021-12-23 16:46:47 -08:00
parent c23a1bfabb
commit f250a33e9b
5 changed files with 14 additions and 2 deletions
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1
src/kernel/cpu.h
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@@ -28,6 +28,7 @@ struct cpu_data
uint32_t reserved; uint32_t reserved;
uintptr_t rsp0; uintptr_t rsp0;
uintptr_t rsp3; uintptr_t rsp3;
uint64_t rflags3;
TCB *tcb; TCB *tcb;
thread *thread; thread *thread;
process *process; process *process;

1
src/kernel/objects/thread.h
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@@ -15,6 +15,7 @@ struct TCB
uintptr_t rsp; uintptr_t rsp;
uintptr_t rsp0; uintptr_t rsp0;
uintptr_t rsp3; uintptr_t rsp3;
uintptr_t rflags3;
uintptr_t pml4; uintptr_t pml4;
uint8_t priority; uint8_t priority;

4
src/kernel/syscall.s
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@@ -31,6 +31,7 @@ syscall_handler_prelude:
swapgs swapgs
mov [gs:CPU_DATA.rsp3], rsp mov [gs:CPU_DATA.rsp3], rsp
mov rsp, [gs:CPU_DATA.rsp0] mov rsp, [gs:CPU_DATA.rsp0]
mov [gs:CPU_DATA.rflags3], r11
push rcx push rcx
push rbp push rbp
@@ -44,7 +45,6 @@ syscall_handler_prelude:
mov rcx, r10 mov rcx, r10
push rbx push rbx
push r11
push r12 push r12
push r13 push r13
push r14 push r14
@@ -76,12 +76,12 @@ kernel_to_user_trampoline:
pop r14 pop r14
pop r13 pop r13
pop r12 pop r12
pop r11
pop rbx pop rbx
pop rbp pop rbp
pop rcx pop rcx
mov r11, [gs:CPU_DATA.rflags3]
mov [gs:CPU_DATA.rsp0], rsp mov [gs:CPU_DATA.rsp0], rsp
mov rsp, [gs:CPU_DATA.rsp3] mov rsp, [gs:CPU_DATA.rsp3]

8
src/kernel/task.s
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@@ -20,6 +20,10 @@ task_switch:
mov rcx, [gs:CPU_DATA.rsp3] ; rcx: current task's saved user rsp mov rcx, [gs:CPU_DATA.rsp3] ; rcx: current task's saved user rsp
mov [rax + TCB.rsp3], rcx mov [rax + TCB.rsp3], rcx
; Copy off saved user rflags
mov rcx, [gs:CPU_DATA.rflags3] ; rcx: current task's saved user rflags
mov [rax + TCB.rflags3], rcx
; Install next task's TCB ; Install next task's TCB
mov [gs:CPU_DATA.tcb], rdi ; rdi: next TCB (function param) mov [gs:CPU_DATA.tcb], rdi ; rdi: next TCB (function param)
mov rsp, [rdi + TCB.rsp] ; next task's stack pointer mov rsp, [rdi + TCB.rsp] ; next task's stack pointer
@@ -37,6 +41,10 @@ task_switch:
mov rcx, [rdi + TCB.rsp3] ; rcx: new task's saved user rsp mov rcx, [rdi + TCB.rsp3] ; rcx: new task's saved user rsp
mov [gs:CPU_DATA.rsp3], rcx mov [gs:CPU_DATA.rsp3], rcx
; Update saved user rflags
mov rcx, [rdi + TCB.rflags3] ; rcx: new task's saved user rflags
mov [gs:CPU_DATA.rflags3], rcx
; check if we need to update CR3 ; check if we need to update CR3
mov rdx, cr3 ; rdx: old CR3 mov rdx, cr3 ; rdx: old CR3
cmp rax, rdx cmp rax, rdx

2
src/kernel/tasking.inc
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@@ -2,6 +2,7 @@ struc TCB
.rsp: resq 1 .rsp: resq 1
.rsp0: resq 1 .rsp0: resq 1
.rsp3: resq 1 .rsp3: resq 1
.rflags3: resq 1
.pml4: resq 1 .pml4: resq 1
endstruc endstruc
@@ -12,6 +13,7 @@ struc CPU_DATA
.reserved resd 1 .reserved resd 1
.rsp0: resq 1 .rsp0: resq 1
.rsp3: resq 1 .rsp3: resq 1
.rflags3: resq 1
.tcb: resq 1 .tcb: resq 1
.thread: resq 1 .thread: resq 1
.process: resq 1 .process: resq 1