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feat(usermode): usermode code execution, usermode GDT segments #81

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Merged
merged 1 commit into from
Jul 25, 2024
Merged

feat(usermode): usermode code execution, usermode GDT segments #81

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44 changes: 7 additions & 37 deletions src/fzboot/irq/manager.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,7 +37,7 @@ use crate::{
x86::{
apic::local_apic::InterruptVector,
descriptors::{
gdt::SegmentSelector,
gdt::KERNEL_CODE_SELECTOR,
idt::{GateDescriptor, GateType, InterruptDescriptorTable},
},
int::{disable_interrupts, enable_interrupts, interrupts_disabled},
Expand Down Expand Up @@ -166,12 +166,7 @@ impl<A: MemoryAddress> InterruptManager<A> {
.with_dpl(PrivilegeLevel::Ring0)
.with_offset(handler_ptr)
.with_present(true)
.with_segment_selector(
SegmentSelector::gdt_selector()
.with_index(0x10)
.expect("invalid segment selector while registering static handler")
.with_rpl(PrivilegeLevel::Ring0),
)
.with_segment_selector(*KERNEL_CODE_SELECTOR)
} else {
let handler_ptr = PhyAddr::new(
u64::try_from(default_handler_ptr as usize).expect("invalid handler pointer"),
Expand All @@ -181,12 +176,7 @@ impl<A: MemoryAddress> InterruptManager<A> {
.with_dpl(PrivilegeLevel::Ring0)
.with_offset(handler_ptr)
.with_present(true)
.with_segment_selector(
SegmentSelector::gdt_selector()
.with_index(0x10)
.expect("invalid segment selector while registering static handler")
.with_rpl(PrivilegeLevel::Ring0),
)
.with_segment_selector(*KERNEL_CODE_SELECTOR)
};

// Setup default handlers for every interrupt vector when first loading the table.
Expand Down Expand Up @@ -309,12 +299,7 @@ impl<A: MemoryAddress> InterruptManager<A> {
.with_dpl(PrivilegeLevel::Ring0)
.with_offset(handler_ptr)
.with_present(true)
.with_segment_selector(
SegmentSelector::gdt_selector()
.with_index(0x10)
.expect("invalid segment selector while registering static handler")
.with_rpl(PrivilegeLevel::Ring0),
)
.with_segment_selector(*KERNEL_CODE_SELECTOR)
} else {
let handler_ptr = PhyAddr::new(
u64::try_from(runtime_entry_ptr as usize).expect("invalid handler pointer"),
Expand All @@ -324,12 +309,7 @@ impl<A: MemoryAddress> InterruptManager<A> {
.with_dpl(PrivilegeLevel::Ring0)
.with_offset(handler_ptr)
.with_present(true)
.with_segment_selector(
SegmentSelector::gdt_selector()
.with_index(0x10)
.expect("invalid segment selector while registering static handler")
.with_rpl(PrivilegeLevel::Ring0),
)
.with_segment_selector(*KERNEL_CODE_SELECTOR)
};

self.idt
Expand Down Expand Up @@ -400,12 +380,7 @@ impl<A: MemoryAddress> InterruptManager<A> {
.with_dpl(PrivilegeLevel::Ring0)
.with_offset(handler_ptr)
.with_present(true)
.with_segment_selector(
SegmentSelector::gdt_selector()
.with_index(0x10)
.expect("invalid segment selector while registering static handler")
.with_rpl(PrivilegeLevel::Ring0),
)
.with_segment_selector(*KERNEL_CODE_SELECTOR)
} else {
let handler_ptr =
PhyAddr::new(u64::try_from(handler as usize).expect("invalid handler pointer"));
Expand All @@ -414,12 +389,7 @@ impl<A: MemoryAddress> InterruptManager<A> {
.with_dpl(PrivilegeLevel::Ring0)
.with_offset(handler_ptr)
.with_present(true)
.with_segment_selector(
SegmentSelector::gdt_selector()
.with_index(0x10)
.expect("invalid segment selector while registering static handler")
.with_rpl(PrivilegeLevel::Ring0),
)
.with_segment_selector(*KERNEL_CODE_SELECTOR)
};

self.idt
Expand Down
71 changes: 70 additions & 1 deletion src/fzboot/irq/mod.rs
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Original file line number Diff line number Diff line change
@@ -1,3 +1,5 @@
use core::arch::asm;

use crate::io::outb;
use crate::io::IOPort;
use crate::mem::VirtAddr;
Expand All @@ -15,7 +17,7 @@ pub mod handlers;
///
/// Interrupt handlers receive this structure as their first argument.
#[repr(C)]
#[derive(Clone, Copy, Debug)]
#[derive(Clone, Copy, Debug, Default)]
pub struct InterruptStackFrame {
/// Saved content of the `RIP` (_instruction pointer_ register) prior to the interrupt.
pub(crate) rip: VirtAddr,
Expand All @@ -36,6 +38,73 @@ pub struct InterruptStackFrame {
pub(crate) registers: GeneralPurposeRegisters,
}

impl InterruptStackFrame {
/// Performs an `iret`.
///
/// Restores the previous execution context using the value defined in the structure.
///
/// Used to return to original execution context after an interrupt was processed.
/// Can also be used to change the current privilege level (`CPL`) of the CPU.
pub unsafe fn iret(&self) {
#[cfg(target_arch = "x86_64")]
unsafe {
asm!("push {0:r}",
"push {1:r}",
"push {2:r}",
"push {3:r}",
"push {4:r}",
"iretq",
in(reg) self.stack_segment,
in(reg) u64::from(self.stack_ptr),
in(reg) self.rflags,
in(reg) self.cs,
in(reg) u64::from(self.rip),
options(noreturn)
)
}
}

/// Performs an `iret`, preserving the current value of `RFLAGS` (and of the stack pointer, if `stack_ptr_override` is set to false).
///
/// Restores the previous execution context using the value defined in the structure.
///
/// Used to return to original execution context after an interrupt was processed.
/// Can also be used to change the current privilege level (`CPL`) of the CPU.
pub unsafe fn iret_preserve_flags(&self, stack_ptr_override: bool) -> ! {
// emulates a fake InterruptStackFrame with data and code segment selector set to `CPL` = 3
#[cfg(target_arch = "x86_64")]
unsafe {
if !stack_ptr_override {
asm!("push {0:r}",
"push rsp",
"pushfq",
"push {1:r}",
"push {2:r}",
"iretq",
in(reg) self.stack_segment,
in(reg) self.cs,
in(reg) u64::from(self.rip),
options(noreturn)
)
} else {
asm!("push {0:r}",
"push {1:r}",
"pushfq",
"push {2:r}",
"push {3:r}",
"iretq",
in(reg) self.stack_segment,
in(reg) u64::from(self.stack_ptr),
in(reg) self.cs,
in(reg) u64::from(self.rip),
options(noreturn))
}
}

unreachable!()
}
}

/// Content of the _Exception Stack Frame_, set up by the CPU when an exception that defines an error code
/// is raised.
///
Expand Down
4 changes: 2 additions & 2 deletions src/fzboot/kernel/src/main.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,7 @@ use fzboot::{
},
video,
x86::{
descriptors::gdt::{long_init_gdt, LONG_GDT_ADDR},
descriptors::gdt::{kernel_init_gdt, LONG_GDT_ADDR},
int::enable_interrupts,
paging::{
get_memory_mapper, init_global_mapper,
Expand Down Expand Up @@ -93,7 +93,7 @@ unsafe fn mem_init(mb_information: &mb_information::MultibootInformation) {
.as_mut_ptr(),
);

long_init_gdt(
kernel_init_gdt(
PhysicalMemoryMapping::KERNEL_DEFAULT_MAPPING.convert(PhyAddr::new(LONG_GDT_ADDR)),
);

Expand Down
2 changes: 1 addition & 1 deletion src/mem/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -117,7 +117,7 @@ impl TryFrom<Alignment> for u64 {
}
}

#[derive(Clone, Copy, Debug, PartialEq, PartialOrd)]
#[derive(Clone, Copy, Debug, Default, PartialEq, PartialOrd)]
pub struct VirtAddr(u64);

impl VirtAddr {
Expand Down
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