Trapframe

https://docs.rs/trapframe/
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Trapframe is a Rust library providing user-space context switching and trap frame handling across...
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### UserContext::get_syscall_args

Source: https://docs.rs/trapframe/latest/trapframe/struct.UserContext.html

Get syscall args.

```APIDOC
## get_syscall_args

### Description
Get syscall args.

### Method
Rust method

### Signature
`pub fn get_syscall_args(&self) -> [usize; 6]`

### Parameters
- `self` (`&UserContext`) - Required - The user context to read from.

### Returns
- `[usize; 6]` - An array of six syscall arguments.

```

--------------------------------

### Replace syscall instruction

Source: https://docs.rs/trapframe/latest/trapframe/fn.syscall_fn_entry.html

Example showing the replacement of a syscall instruction with a call to syscall_fn_entry.

```asm
syscall
call syscall_fn_entry
```

--------------------------------

### UserContext::get_syscall_ret

Source: https://docs.rs/trapframe/latest/trapframe/struct.UserContext.html

Get return value of syscall.

```APIDOC
## get_syscall_ret

### Description
Get return value of syscall.

### Method
Rust method

### Signature
`pub fn get_syscall_ret(&self) -> usize`

### Parameters
- `self` (`&UserContext`) - Required - The user context to read from.

### Returns
- `usize` - The syscall return value.

```

--------------------------------

### Common assembly for syscall_fn_entry trap frame setup

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/fncall.rs.html

Assembly for the syscall_fn_entry symbol that saves the stack pointer, switches to the kernel stack, and pushes the trap frame (struct GeneralRegs) including gs_base, user fsbase, rflags, rip, and r15.

```assembly
global_asm!(
    r#"
syscall_fn_entry:
    # save rsp
    lea r11, [rsp + 8]      # save rsp to r11 (clobber)

    SWITCH_TO_KERNEL_STACK
    pop rsp
    lea rsp, [rsp + 20*8]   # rsp = top of trap frame

    # push trap frame (struct GeneralRegs)
    push 0                  # ignore gs_base
    PUSH_USER_FSBASE
    pushfq                  # push rflags
    push [r11 - 8]          # push rip
    push r15
"#
);
```

--------------------------------

### UserContext methods for syscall and register manipulation

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Provides methods to get and set syscall number, return value, and arguments, as well as set and get instruction pointer, stack pointer, and TLS pointer. These methods operate on the general registers within UserContext.

```rust
impl UserContext {
    /// Get number of syscall
    pub fn get_syscall_num(&self) -> usize {
        self.general.rax
    }

    /// Get return value of syscall
    pub fn get_syscall_ret(&self) -> usize {
        self.general.rax
    }

    /// Set return value of syscall
    pub fn set_syscall_ret(&mut self, ret: usize) {
        self.general.rax = ret;
    }

    /// Get syscall args
    pub fn get_syscall_args(&self) -> [usize; 6] {
        [
            self.general.rdi,
            self.general.rsi,
            self.general.rdx,
            self.general.r10,
            self.general.r8,
            self.general.r9,
        ]
    }

    /// Set instruction pointer
    pub fn set_ip(&mut self, ip: usize) {
        self.general.rip = ip;
    }

    /// Set stack pointer
    pub fn set_sp(&mut self, sp: usize) {
        self.general.rsp = sp;
    }

    /// Get stack pointer
    pub fn get_sp(&self) -> usize {
        self.general.rsp
    }

    /// Set tls pointer
    pub fn set_tls(&mut self, tls: usize) {
        self.general.fsbase = tls;
    }
}
```

--------------------------------

### UserContext::get_syscall_num

Source: https://docs.rs/trapframe/latest/trapframe/struct.UserContext.html

Get number of syscall.

```APIDOC
## get_syscall_num

### Description
Get number of syscall.

### Method
Rust method

### Signature
`pub fn get_syscall_num(&self) -> usize`

### Parameters
- `self` (`&UserContext`) - Required - The user context to read from.

### Returns
- `usize` - The syscall number.

```

--------------------------------

### UserContext::get_syscall_args

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Returns the syscall arguments from the user context as an array of six usize values, extracted from the general-purpose registers.

```APIDOC
## UserContext::get_syscall_args

### Description
Returns the syscall arguments from the user context as an array of six usize values, extracted from the general-purpose registers.

### Signature
```rust
pub fn get_syscall_args(&self) -> [usize; 6]
```

### Parameters
- `&self` - The user context.

### Return Value
- `[usize; 6]` - The syscall arguments in order: rdi, rsi, rdx, r10, r8, r9.
```

--------------------------------

### init

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Initializes interrupt handling on x86_64 by disabling interrupts, setting up a new GDT, TSS, IDT, and enabling the syscall instruction. This function is unsafe and should only be called once during system initialization.

```APIDOC
## init

### Description
Initializes interrupt handling on x86_64. This function will disable interrupts, switch to a new GDT, TSS, and IDT, and enable the syscall instruction.

### Safety
This function is unsafe because it modifies critical system state (GDT, IDT, TSS, and MSRs) and must only be called once during early initialization.

### Signature
```rust
pub unsafe fn init()
```

### Parameters
None

### Return Value
None

### Notes
- Available on target_os = "none" or "uefi".
```

--------------------------------

### UserContext::run_fncall

Source: https://docs.rs/trapframe/latest/trapframe/struct.UserContext.html

Go to user context by function return, within the same privilege level. User program should call syscall_fn_entry() to return back. Trap reason and error code will always be set to 0x100 and 0.

```APIDOC
## run_fncall

### Description
Go to user context by function return, within the same privilege level. User program should call `syscall_fn_entry()` to return back. Trap reason and error code will always be set to 0x100 and 0.

### Method
Rust method

### Signature
`pub fn run_fncall(&mut self)`

### Parameters
- `self` (`&mut UserContext`) - Required - The user context to operate on.

### Returns
None

```

--------------------------------

### UserContext::set_ip

Source: https://docs.rs/trapframe/latest/trapframe/struct.UserContext.html

Set instruction pointer.

```APIDOC
## set_ip

### Description
Set instruction pointer.

### Method
Rust method

### Signature
`pub fn set_ip(&mut self, ip: usize)`

### Parameters
- `self` (`&mut UserContext`) - Required - The user context to modify.
- `ip` (`usize`) - Required - The instruction pointer value to set.

### Returns
None

```

--------------------------------

### Architecture-specific module loading in lib.rs

Source: https://docs.rs/trapframe/latest/src/trapframe/lib.rs.html

This snippet demonstrates how the crate uses conditional compilation attributes to select the correct architecture module for the target platform.

```rust
1#![no_std]
2#![deny(warnings)]
3
4extern crate alloc;
5
6#[cfg(target_arch = "x86_64")]
7#[path = "arch/x86_64/mod.rs"]
8mod arch;
9
10#[cfg(any(target_arch = "riscv32", target_arch = "riscv64"))]
11#[path = "arch/riscv/mod.rs"]
12mod arch;
13
14#[cfg(target_arch = "mips")]
15#[path = "arch/mipsel/mod.rs"]
16pub mod arch;
17
18#[cfg(target_arch = "aarch64")]
19#[path = "arch/aarch64/mod.rs"]
20pub mod arch;
21
22pub use arch::*;
```

--------------------------------

### Linux assembly for syscall_fn_entry and syscall_fn_return

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/fncall.rs.html

Assembly for Linux (target_os = "linux") defining macros to switch to kernel stack, save kernel stack, push/pop user FS base, and the global symbols syscall_fn_entry and syscall_fn_return. Uses SYS_arch_prctl with SET_FS to switch FS base.

```assembly
// User: (musl)
// - fs:0  (pthread.self)       = user fsbase
// - fs:48 (pthread.canary2)    = kernel fsbase
//
// Kernel: (glibc)
// - fs:0  (pthread.self)       = kernel fsbase
// - fs:64 (pthread.???)        = kernel stack
// - fs:72 (pthread.???)        = init user fsbase
//
#[cfg(target_os = "linux")]
global_asm!(
    r#"
.macro SWITCH_TO_KERNEL_STACK
    mov rsp, fs:48          # rsp = kernel fsbase
    mov rsp, [rsp + 64]     # rsp = kernel stack
.endm
.macro SAVE_KERNEL_STACK
    mov fs:64, rsp
.endm
.macro PUSH_USER_FSBASE
    push fs:0
.endm
.macro SWITCH_TO_KERNEL_FSBASE
    mov eax, 158            # SYS_arch_prctl
    mov edi, 0x1002         # SET_FS
    mov rsi, fs:48          # rsi = kernel fsbase
    syscall
.endm
.macro POP_USER_FSBASE
    mov rsi, [rsp + 18 * 8] # rsi = user fsbase
    mov rdx, fs:0           # rdx = kernel fsbase
    test rsi, rsi
    jnz 1f                  # if not 0, goto set
0:  lea rsi, [rdx + 72]     # rsi = init user fsbase
    mov [rsi], rsi          # user_fs:0 = user fsbase
1:  mov eax, 158            # SYS_arch_prctl
    mov edi, 0x1002         # SET_FS
    syscall                 # set fsbase
    mov fs:48, rdx          # user_fs:48 = kernel fsbase
.endm

.global syscall_fn_entry
.global syscall_fn_return
"#
);
```

--------------------------------

### macOS assembly for syscall_fn_entry and syscall_fn_return

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/fncall.rs.html

Assembly for macOS (target_os = "macos") defining macros to switch to kernel stack, save kernel stack, push/pop user GS base, and the global symbols _syscall_fn_entry, syscall_fn_entry, _syscall_fn_return, syscall_fn_return. Uses syscall 0x3000003 to set GS base.

```assembly
// User: (musl)
// - gs:0   (pthread.self)      = user gsbase
// - gs:48  (pthread.canary2)   = kernel gsbase
//
// Kernel: (darwin)
// - gs:0   (pthread.tsd[self]) = kernel gsbase - 224
// - gs:48  (pthread.tsd[6])    = kernel stack
// - gs:240 (pthread.tsd[30])   = init user fsbase
//
// Ref:
// - Set gsbase:
//   - https://gist.github.com/aras-p/5389747
// - Get gsbase:
//   - https://github.com/DynamoRIO/dynamorio/issues/1568#issuecomment-239819506
//   - https://github.com/apple/darwin-libpthread/blob/03c4628c8940cca6fd6a82957f683af804f62e7f/src/internal.h#L241
#[cfg(target_os = "macos")]
global_asm!(
    r#"
.macro SWITCH_TO_KERNEL_STACK
    mov rsp, gs:48          # rsp = kernel gsbase
    mov rsp, [rsp + 48]     # rsp = kernel stack
.endm
.macro SAVE_KERNEL_STACK
    mov gs:48, rsp
.endm
.macro PUSH_USER_FSBASE
    push gs:0
.endm
.macro SWITCH_TO_KERNEL_FSBASE
    mov rdi, gs:48          # rdi = kernel gsbase
    mov eax, 0x3000003
    syscall                 # set gsbase
.endm
.macro POP_USER_FSBASE
    mov rdi, [rsp + 18 * 8] # rdi = user gsbase
    mov rsi, gs:0
    add rsi, 224            # rsi = kernel gsbase
    test rdi, rdi
    jnz 1f                  # if not 0, goto set
0:  lea rdi, [rsi + 30*8]   # rdi = init user gsbase
                            #     = pthread.tsd[30] (kernel gsbase + 30 * 8)
    mov [rdi], rdi          # user_gs:0 = user gsbase
1:  mov eax, 0x3000003
    syscall                 # set gsbase
    mov gs:48, rsi          # user_gs:48 = kernel gsbase
.endm

.global _syscall_fn_entry
.global syscall_fn_entry
.global _syscall_fn_return
.set _syscall_fn_entry, syscall_fn_entry
.set _syscall_fn_return, syscall_fn_return
"#
);
```

--------------------------------

### UserContext::set_syscall_ret

Source: https://docs.rs/trapframe/latest/trapframe/struct.UserContext.html

Set return value of syscall.

```APIDOC
## set_syscall_ret

### Description
Set return value of syscall.

### Method
Rust method

### Signature
`pub fn set_syscall_ret(&mut self, ret: usize)`

### Parameters
- `self` (`&mut UserContext`) - Required - The user context to modify.
- `ret` (`usize`) - Required - The return value to set.

### Returns
None

```

--------------------------------

### UserContext::get_sp

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Returns the current stack pointer (RSP) from the user context.

```APIDOC
## UserContext::get_sp

### Description
Returns the current stack pointer (RSP) from the user context.

### Signature
```rust
pub fn get_sp(&self) -> usize
```

### Parameters
- `&self` - The user context.

### Return Value
- `usize` - The current stack pointer value.
```

--------------------------------

### x86_64 Assembly Register Management

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/fncall.rs.html

Assembly routines for pushing registers, switching stacks, and returning to Rust, including the syscall_fn_return entry point.

```asm
160    push r14
161    push r13
162    push r12
163    push r11
164    push r10
165    push r9
166    push r8
167    push r11                # push rsp
168    push rbp
169    push rdi
170    push rsi
171    push rdx
172    push rcx
173    push rbx
174    push rax
175
176    # restore callee-saved registers
177    SWITCH_TO_KERNEL_STACK
178    pop rbx
179    pop rbx
180    pop rbp
181    pop r12
182    pop r13
183    pop r14
184    pop r15
185
186    SWITCH_TO_KERNEL_FSBASE
187
188    # go back to Rust
189    ret
190
191    # extern "sysv64" fn syscall_fn_return(&mut UserContext)
192syscall_fn_return:
193    # save callee-saved registers
194    push r15
195    push r14
196    push r13
197    push r12
198    push rbp
199    push rbx
200
201    push rdi
202    SAVE_KERNEL_STACK
203    mov rsp, rdi
204
205    POP_USER_FSBASE
206
207    # pop trap frame (struct GeneralRegs)
208    pop rax
209    pop rbx
210    pop rcx
211    pop rdx
212    pop rsi
213    pop rdi
214    pop rbp
215    pop r8                  # skip rsp
216    pop r8
217    pop r9
218    pop r10
219    pop r11
220    pop r12
221    pop r13
222    pop r14
223    pop r15
224    pop r11                 # r11 = rip. FIXME: don't overwrite r11!
225    popfq                   # pop rflags
226    mov rsp, [rsp - 8*11]   # restore rsp
227    jmp r11                 # restore rip
```

--------------------------------

### UserContext and GeneralRegs structures for user space context

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Defines UserContext with general registers, trap number, and error code, and GeneralRegs with all x86_64 general-purpose registers plus rip, rflags, fsbase, and gsbase. Both are repr(C) and derive common traits.

```rust
/// User space context
#[derive(Debug, Default, Clone, Copy, Eq, PartialEq)]
#[repr(C)]
pub struct UserContext {
    pub general: GeneralRegs,
    pub trap_num: usize,
    pub error_code: usize,
}

/// General registers
#[derive(Debug, Default, Clone, Copy, Eq, PartialEq)]
#[repr(C)]
pub struct GeneralRegs {
    pub rax: usize,
    pub rbx: usize,
    pub rcx: usize,
    pub rdx: usize,
    pub rsi: usize,
    pub rdi: usize,
    pub rbp: usize,
    pub rsp: usize,
    pub r8: usize,
    pub r9: usize,
    pub r10: usize,
    pub r11: usize,
    pub r12: usize,
    pub r13: usize,
    pub r14: usize,
    pub r15: usize,
    pub rip: usize,
    pub rflags: usize,
    pub fsbase: usize,
    pub gsbase: usize,
}
```

--------------------------------

### Rust implementation of run_fncall and syscall_fn_entry

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/fncall.rs.html

Defines the syscall_fn_entry and syscall_fn_return extern functions, and the run_fncall method that calls syscall_fn_return and sets trap_num to 0x100 and error_code to 0. The user program should call syscall_fn_entry() to return back.

```rust
//! Switch context by function call within the same privilege level.
//!
//! # Assumption
//!
//! This module suppose you are running kernel on Linux or macOS with glibc,
//! and your user program is based on musl libc.
//!
//! Because we will store values in their pthread structure.

use super::UserContext;
use core::arch::global_asm;

extern "sysv64" {
    /// The syscall entry of function call.
    ///
    /// # Usage
    ///
    /// Replace `syscall` instruction by a `call` instruction.
    ///
    /// ```asm
    /// syscall
    /// call syscall_fn_entry
    /// ```
    pub fn syscall_fn_entry();

    fn syscall_fn_return(regs: &mut UserContext);
}

impl UserContext {
    /// Go to user context by function return, within the same privilege level.
    ///
    /// User program should call `syscall_fn_entry()` to return back.
    /// Trap reason and error code will always be set to 0x100 and 0.
    pub fn run_fncall(&mut self) {
        unsafe {
            syscall_fn_return(self);
        }
        self.trap_num = 0x100;
        self.error_code = 0;
    }
}
```

--------------------------------

### UserContext::set_ip

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Sets the instruction pointer (RIP) in the user context.

```APIDOC
## UserContext::set_ip

### Description
Sets the instruction pointer (RIP) in the user context.

### Signature
```rust
pub fn set_ip(&mut self, ip: usize)
```

### Parameters
- `ip` (usize) - The new instruction pointer value.

### Return Value
None
```

--------------------------------

### UserContext::set_tls

Source: https://docs.rs/trapframe/latest/trapframe/struct.UserContext.html

Set tls pointer.

```APIDOC
## set_tls

### Description
Set tls pointer.

### Method
Rust method

### Signature
`pub fn set_tls(&mut self, tls: usize)`

### Parameters
- `self` (`&mut UserContext`) - Required - The user context to modify.
- `tls` (`usize`) - Required - The TLS pointer value to set.

### Returns
None

```

--------------------------------

### Function Call Test Suite

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/fncall.rs.html

Rust test case that initializes a UserContext and verifies register state restoration after executing a function call.

```rust
#[test]
    fn run_fncall() {
        extern "sysv64" {
            fn dump_registers();
        }
        let mut stack = [0u8; 0x1000];
        let mut cx = UserContext {
            general: GeneralRegs {
                rax: 0,
                rbx: 1,
                rcx: 2,
                rdx: 3,
                rsi: 4,
                rdi: 5,
                rbp: 6,
                rsp: stack.as_mut_ptr() as usize + 0x1000,
                r8: 8,
                r9: 9,
                r10: 10,
                r11: 11,
                r12: 12,
                r13: 13,
                r14: 14,
                r15: 15,
                rip: dump_registers as *const () as usize,
                rflags: 0,
                fsbase: 0, // don't set to non-zero garbage value
                gsbase: 0,
            },
            trap_num: 0,
            error_code: 0,
        };
        cx.run_fncall();
        // check restored registers
        let general = unsafe { *(cx.general.rsp as *const GeneralRegs) };
        assert_eq!(
            general,
            GeneralRegs {
                rax: 0,
                rbx: 1,
                rcx: 2,
                rdx: 3,
                rsi: 4,
                rdi: 5,
                rbp: 6,
                // skip rsp
                r8: 8,
                r9: 9,
                r10: 10,
                // skip r11
                r12: 12,
                r13: 13,
                r14: 14,
                r15: 15,
                ..general
            }
        );
        // check saved registers
        assert_eq!(
            cx.general,
            GeneralRegs {
                rax: 10,
                rbx: 11,
                rcx: 12,
                rdx: 13,
                rsi: 14,
                rdi: 15,
                rbp: 16,
                // skip rsp
                r8: 18,
                r9: 19,
                r10: 20,
                // skip r11
                r12: 22,
                r13: 23,
                r14: 24,
                r15: 25,
                ..cx.general
            }
        );
        assert_eq!(cx.trap_num, 0x100);
        assert_eq!(cx.error_code, 0);
    }
```

--------------------------------

### UserContext::set_sp

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Sets the stack pointer (RSP) in the user context.

```APIDOC
## UserContext::set_sp

### Description
Sets the stack pointer (RSP) in the user context.

### Signature
```rust
pub fn set_sp(&mut self, sp: usize)
```

### Parameters
- `sp` (usize) - The new stack pointer value.

### Return Value
None
```

--------------------------------

### UserContext::get_syscall_ret

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Returns the return value of the syscall from the user context, which is stored in the RAX register.

```APIDOC
## UserContext::get_syscall_ret

### Description
Returns the return value of the syscall from the user context, which is stored in the RAX register.

### Signature
```rust
pub fn get_syscall_ret(&self) -> usize
```

### Parameters
- `&self` - The user context.

### Return Value
- `usize` - The syscall return value (value of RAX).
```

--------------------------------

### syscall_fn_entry function signature

Source: https://docs.rs/trapframe/latest/trapframe/fn.syscall_fn_entry.html

The function signature for syscall_fn_entry.

```rust
pub unsafe extern "sysv64" fn syscall_fn_entry()
```

--------------------------------

### syscall_fn_entry

Source: https://docs.rs/trapframe/latest/trapframe

A function that serves as the syscall entry point for function calls. It is marked as unsafe (⚠) and is part of the public API.

```APIDOC
## Function: syscall_fn_entry

### Description
The syscall entry of function call. This function is marked as unsafe (⚠).

### Safety
This function is unsafe and must be called with appropriate precautions.

### Parameters
No parameters are documented in the source.

### Returns
No return value is documented in the source.

```

--------------------------------

### UserContext

Source: https://docs.rs/trapframe/latest/trapframe

A struct representing user space context. It is part of the public API for managing user context during context switches or syscalls.

```APIDOC
## Struct: UserContext

### Description
Represents user space context.

### Fields
No fields are documented in the source.

### Usage
This struct is part of the trapframe crate's public API and can be used to manage user space context.

```

--------------------------------

### UserContext::get_syscall_num

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Returns the syscall number from the user context, which is stored in the RAX register.

```APIDOC
## UserContext::get_syscall_num

### Description
Returns the syscall number from the user context, which is stored in the RAX register.

### Signature
```rust
pub fn get_syscall_num(&self) -> usize
```

### Parameters
- `&self` - The user context.

### Return Value
- `usize` - The syscall number (value of RAX).
```

--------------------------------

### Unsafe init function for interrupt handling on x86_64

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Initializes interrupt handling by disabling interrupts, then initializing GDT, IDT, and syscall. This function is unsafe and only available for none or uefi targets. It switches to new GDT, TSS, and IDT, and enables the syscall instruction.

```rust
#[cfg(any(target_os = "none", target_os = "uefi"))]
pub unsafe fn init() {
    x86_64::instructions::interrupts::disable();
    gdt::init();
    idt::init();
    syscall::init();
}
```

--------------------------------

### UserContext::set_syscall_ret

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Sets the return value of the syscall in the user context by writing to the RAX register.

```APIDOC
## UserContext::set_syscall_ret

### Description
Sets the return value of the syscall in the user context by writing to the RAX register.

### Signature
```rust
pub fn set_syscall_ret(&mut self, ret: usize)
```

### Parameters
- `ret` (usize) - The return value to set.

### Return Value
None
```

--------------------------------

### Module declarations and conditional compilation for x86_64

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Declares submodules with conditional compilation attributes based on target OS and feature flags. Includes fncall for Linux/macOS, and gdt, idt, ioport, syscall, trap for none/uefi targets. Re-exports syscall_fn_entry and TrapFrame conditionally.

```rust
#[cfg(any(target_os = "linux", target_os = "macos"))]
mod fncall;
#[cfg(any(target_os = "none", target_os = "uefi"))]
mod gdt;
#[cfg(any(target_os = "none", target_os = "uefi"))]
mod idt;
#[cfg(feature = "ioport_bitmap")]
#[cfg(any(target_os = "none", target_os = "uefi"))]
pub mod ioport;
#[cfg(any(target_os = "none", target_os = "uefi"))]
mod syscall;
#[cfg(any(target_os = "none", target_os = "uefi"))]
mod trap;

#[cfg(any(target_os = "linux", target_os = "macos"))]
pub use fncall::syscall_fn_entry;
#[cfg(any(target_os = "none", target_os = "uefi"))]
pub use trap::TrapFrame;
```

--------------------------------

### UserContext::set_tls

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/mod.rs.html

Sets the thread-local storage (TLS) pointer by writing to the FS base register.

```APIDOC
## UserContext::set_tls

### Description
Sets the thread-local storage (TLS) pointer by writing to the FS base register.

### Signature
```rust
pub fn set_tls(&mut self, tls: usize)
```

### Parameters
- `tls` (usize) - The new TLS pointer value.

### Return Value
None
```

--------------------------------

### Mock Register Dump Assembly

Source: https://docs.rs/trapframe/latest/src/trapframe/arch/x86_64/fncall.rs.html

Assembly code used in tests to simulate a user program dumping registers onto the stack before calling the syscall entry.

```asm
dump_registers:
    push r15
    push r14
    push r13
    push r12
    push r11
    push r10
    push r9
    push r8
    push rsp
    push rbp
    push rdi
    push rsi
    push rdx
    push rcx
    push rbx
    push rax

    add rax, 10
    add rbx, 10
    add rcx, 10
    add rdx, 10
    add rsi, 10
    add rdi, 10
    add rbp, 10
    add r8, 10
    add r9, 10
    add r10, 10
    add r11, 10
    add r12, 10
    add r13, 10
    add r14, 10
    add r15, 10

    call syscall_fn_entry
```

--------------------------------

### UserContext Struct Definition

Source: https://docs.rs/trapframe/latest/trapframe/struct.UserContext.html

The definition of the UserContext struct, which is marked with #[repr(C)] for binary compatibility.

```rust
#[repr(C)]
pub struct UserContext {
    pub general: GeneralRegs,
    pub trap_num: usize,
    pub error_code: usize,
}
```

--------------------------------

### GeneralRegs

Source: https://docs.rs/trapframe/latest/trapframe

A struct representing general registers. It is part of the public API for accessing and manipulating general-purpose registers.

```APIDOC
## Struct: GeneralRegs

### Description
Represents general registers.

### Fields
No fields are documented in the source.

### Usage
This struct is part of the trapframe crate's public API and can be used to access general register state.

```

--------------------------------

### GeneralRegs struct definition

Source: https://docs.rs/trapframe/latest/trapframe/struct.GeneralRegs.html

Defines the GeneralRegs struct with 20 fields representing general-purpose registers (rax, rbx, rcx, rdx, rsi, rdi, rbp, rsp, r8-r15, rip, rflags, fsbase, gsbase). All fields are of type usize. The struct is marked with #[repr(C)] for C-compatible layout.

```rust
#[repr(C)]
pub struct GeneralRegs {Show 20 fields
    pub rax: usize,
    pub rbx: usize,
    pub rcx: usize,
    pub rdx: usize,
    pub rsi: usize,
    pub rdi: usize,
    pub rbp: usize,
    pub rsp: usize,
    pub r8: usize,
    pub r9: usize,
    pub r10: usize,
    pub r11: usize,
    pub r12: usize,
    pub r13: usize,
    pub r14: usize,
    pub r15: usize,
    pub rip: usize,
    pub rflags: usize,
    pub fsbase: usize,
    pub gsbase: usize,
}
```
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