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core: Check the stack is in user memory before changing it to kernel space

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Otherwise, we're just adding the physical base to an address that's already in the higher half.
This commit is contained in:
Gabriel 2025-02-21 18:47:24 +01:00
parent 785335bd9a
commit 8156ff57fe
2 changed files with 15 additions and 2 deletions
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9
core/src/arch/x86_64/thread.zig
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@ -1,7 +1,7 @@
const std = @import("std"); const std = @import("std");
const interrupts = @import("interrupts.zig"); const interrupts = @import("interrupts.zig");
pub inline fn enterTask(regs: *interrupts.InterruptStackFrame, comptime base: u64, directory: u64) noreturn { pub inline fn enterTask(regs: *interrupts.InterruptStackFrame, base: u64, directory: u64) noreturn {
asm volatile ( asm volatile (
\\ addq %[base], %rsp \\ addq %[base], %rsp
\\ push %[ss] \\ push %[ss]
@ -47,6 +47,13 @@ pub fn idleLoop() callconv(.Naked) noreturn {
); );
} }
pub inline fn readStackPointer() usize {
return asm volatile (
\\ mov %rsp, %[result]
: [result] "=r" (-> usize),
);
}
pub fn setAddress(regs: *interrupts.InterruptStackFrame, address: u64) void { pub fn setAddress(regs: *interrupts.InterruptStackFrame, address: u64) void {
regs.rip = address; regs.rip = address;
} }

8
core/src/thread.zig
View File

@ -44,7 +44,13 @@ pub fn enterTask(task: *ThreadControlBlock) noreturn {
task.state = .Running; task.state = .Running;
arch.enterTask(&task.regs, vmm.PHYSICAL_MAPPING_BASE, table.address); // If the stack is in user memory, then we need a pointer to its higher-half version. If it's already in kernel memory, no need to do anything.
var base: usize = 0;
if (arch.readStackPointer() < vmm.PHYSICAL_MAPPING_BASE) {
base += vmm.PHYSICAL_MAPPING_BASE;
}
arch.enterTask(&task.regs, base, table.address);
} }
fn switchTask(regs: *interrupts.InterruptStackFrame, new_task: *ThreadControlBlock) void { fn switchTask(regs: *interrupts.InterruptStackFrame, new_task: *ThreadControlBlock) void {