From 41d5a2a786726b3655b0dd444b77b76ab1aa45f3 Mon Sep 17 00:00:00 2001
From: 4lDO2 <4lDO2@protonmail.com>
Date: Fri, 6 Aug 2021 18:08:04 +0200
Subject: [PATCH] Use naked functions in syscall inst handler too.
---
src/arch/x86_64/gdt.rs | 3 ---
src/arch/x86_64/interrupt/handler.rs | 28 -------------------
src/arch/x86_64/interrupt/syscall.rs | 40 +++++++++++++++++++---------
3 files changed, 27 insertions(+), 44 deletions(-)
diff --git a/src/arch/x86_64/gdt.rs b/src/arch/x86_64/gdt.rs
index 5e974c3d..b55db056 100644
--- a/src/arch/x86_64/gdt.rs
+++ b/src/arch/x86_64/gdt.rs
@@ -78,9 +78,6 @@ pub static mut GDT: [GdtEntry; 10] = [
#[repr(C, align(16))]
pub struct ProcessorControlRegion {
- // NOTE: If you plan to change any fields here, please make sure that you also modify the
- // offsets in the syscall instruction handler accordingly!
-
pub tcb_end: usize,
pub user_rsp_tmp: usize,
pub tss: TssWrapper,
diff --git a/src/arch/x86_64/interrupt/handler.rs b/src/arch/x86_64/interrupt/handler.rs
index 58ee4dd7..4cf27e87 100644
--- a/src/arch/x86_64/interrupt/handler.rs
+++ b/src/arch/x86_64/interrupt/handler.rs
@@ -203,34 +203,6 @@ impl InterruptErrorStack {
}
}
-#[macro_export]
-macro_rules! intel_asm {
- ($($strings:expr,)+) => {
- global_asm!(concat!(
- $($strings),+,
- ));
- };
-}
-#[macro_export]
-macro_rules! function {
- ($name:ident => { $($body:expr,)+ }) => {
- intel_asm!(
- ".global ", stringify!($name), "\n",
- ".type ", stringify!($name), ", @function\n",
- ".section .text.", stringify!($name), ", \"ax\", @progbits\n",
- // Align the function to a 16-byte boundary, padding with multi-byte NOPs.
- ".p2align 4,,15\n",
- stringify!($name), ":\n",
- $($body),+,
- ".size ", stringify!($name), ", . - ", stringify!($name), "\n",
- ".text\n",
- );
- extern "C" {
- pub fn $name();
- }
- };
-}
-
#[macro_export]
macro_rules! push_scratch {
() => { "
diff --git a/src/arch/x86_64/interrupt/syscall.rs b/src/arch/x86_64/interrupt/syscall.rs
index 3fbc49ac..38c78c23 100644
--- a/src/arch/x86_64/interrupt/syscall.rs
+++ b/src/arch/x86_64/interrupt/syscall.rs
@@ -5,7 +5,8 @@ use crate::{
syscall,
syscall::flag::{PTRACE_FLAG_IGNORE, PTRACE_STOP_PRE_SYSCALL, PTRACE_STOP_POST_SYSCALL},
};
-use x86::msr;
+use memoffset::offset_of;
+use x86::{bits64::task::TaskStateSegment, msr, segmentation::SegmentSelector};
pub unsafe fn init() {
// IA32_STAR[31:0] are reserved.
@@ -58,16 +59,18 @@ pub unsafe extern "C" fn __inner_syscall_instruction(stack: *mut InterruptStack)
});
}
-function!(syscall_instruction => {
+#[naked]
+pub unsafe extern "C" fn syscall_instruction() {
+ asm!(concat!(
// Yes, this is magic. No, you don't need to understand
"
swapgs // Set gs segment to TSS
- mov gs:[0x08], rsp // Save userspace stack pointer
- mov rsp, gs:[0x14] // Load kernel stack pointer
- push QWORD PTR 5 * 8 + 3 // Push fake userspace SS (resembling iret frame)
- push QWORD PTR gs:[0x08] // Push userspace rsp
+ mov gs:[{sp}], rsp // Save userspace stack pointer
+ mov rsp, gs:[{ksp}] // Load kernel stack pointer
+ push QWORD PTR {ss_sel} // Push fake userspace SS (resembling iret frame)
+ push QWORD PTR gs:[{sp}] // Push userspace rsp
push r11 // Push rflags
- push QWORD PTR 6 * 8 + 3 // Push fake CS (resembling iret stack frame)
+ push QWORD PTR {cs_sel} // Push fake CS (resembling iret stack frame)
push rcx // Push userspace return pointer
",
@@ -113,8 +116,8 @@ function!(syscall_instruction => {
pop rcx // Pop userspace return pointer
add rsp, 8 // Pop fake userspace CS
pop r11 // Pop rflags
- pop QWORD PTR gs:[0x08] // Pop userspace stack pointer
- mov rsp, gs:[0x08] // Restore userspace stack pointer
+ pop QWORD PTR gs:[{sp}] // Pop userspace stack pointer
+ mov rsp, gs:[{sp}] // Restore userspace stack pointer
swapgs // Restore gs from TSS to user data
sysretq // Return into userspace; RCX=>RIP,R11=>RFLAGS
@@ -125,8 +128,16 @@ function!(syscall_instruction => {
xor r11, r11
swapgs
iretq
- ",
-});
+ "),
+
+ sp = const(offset_of!(gdt::ProcessorControlRegion, user_rsp_tmp)),
+ ksp = const(offset_of!(gdt::ProcessorControlRegion, tss) + offset_of!(TaskStateSegment, rsp)),
+ ss_sel = const(SegmentSelector::new(gdt::GDT_USER_DATA as u16, x86::Ring::Ring3).bits()),
+ cs_sel = const(SegmentSelector::new(gdt::GDT_USER_CODE as u16, x86::Ring::Ring3).bits()),
+
+ options(noreturn),
+ );
+}
interrupt_stack!(syscall, |stack| {
with_interrupt_stack!(|stack| {
@@ -150,7 +161,9 @@ interrupt_stack!(syscall, |stack| {
})
});
-function!(clone_ret => {
+#[naked]
+pub unsafe extern "C" fn clone_ret() {
+ asm!(concat!(
// The address of this instruction is injected by `clone` in process.rs, on
// top of the stack syscall->inner in this file, which is done using the rbp
// register we save there.
@@ -165,4 +178,5 @@ function!(clone_ret => {
"pop rbp\n",
// ...and we return to the address at the top of the stack
"ret\n",
-});
+ ), options(noreturn));
+}
--
GitLab