Support dynamic relocation in libuser

Makefile.toml

@@ -14,10 +14,6 @@ script = ["cp linker-scripts/bootstrap.ld link.T"]
 workspace = false
 script = ["cp linker-scripts/kernel.ld    link.T"]
 
-[tasks.userspace-linker]
-workspace = false
-script = ["cp linker-scripts/userspace.ld    link.T"]
-
 [tasks.install-rust-src]
 install_crate = { rustup_component_name = "rust-src" }
 
@@ -55,72 +51,72 @@ args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-kernel", "--r
 [tasks.vi]
 workspace = false
 description = "Compiles sunrise-vi"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-vi"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-vi"]
 
 [tasks.vi-release]
 workspace = false
 description = "Compiles sunrise-vi"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-vi", "--release"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-vi", "--release"]
 
 [tasks.sm]
 workspace = false
 description = "Compiles sunrise-sm"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-sm"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-sm"]
 
 [tasks.sm-release]
 workspace = false
 description = "Compiles sunrise-sm"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-sm", "--release"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-sm", "--release"]
 
 [tasks.shell]
 workspace = false
 description = "Compiles sunrise-shell"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-shell"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-shell"]
 
 [tasks.shell-release]
 workspace = false
 description = "Compiles sunrise-shell"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-shell", "--release"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-shell", "--release"]
 
 [tasks.clock]
 workspace = false
 description = "Compiles sunrise-clock"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-clock"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-clock"]
 
 [tasks.clock-release]
 workspace = false
 description = "Compiles sunrise-clock"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-clock", "--release"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-clock", "--release"]
 
 [tasks.ahci]
 workspace = false
 description = "Compiles sunrise-ahci"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-ahci"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-ahci"]
 
 [tasks.ahci-release]
 workspace = false
 description = "Compiles sunrise-ahci"
-dependencies = ["userspace-linker", "install-rust-src"]
+dependencies = ["install-rust-src"]
 command = "cargo"
-args = ["xbuild", "--target=i386-unknown-none", "--package=sunrise-ahci", "--release"]
+args = ["xbuild", "--target=i386-unknown-none-user", "--package=sunrise-ahci", "--release"]
 
 [tasks.userspace]
 workspace = false
@@ -140,11 +136,11 @@ script = [
 '''
 cp target/i386-unknown-none/debug/sunrise-bootstrap isofiles/boot/
 cp target/i386-unknown-none/debug/sunrise-kernel    isofiles/boot/
-cp target/i386-unknown-none/debug/sunrise-shell     isofiles/boot/
-cp target/i386-unknown-none/debug/sunrise-clock     isofiles/boot/
-cp target/i386-unknown-none/debug/sunrise-sm        isofiles/boot/
-cp target/i386-unknown-none/debug/sunrise-vi        isofiles/boot/
-cp target/i386-unknown-none/debug/sunrise-ahci      isofiles/boot/
+cp target/i386-unknown-none-user/debug/sunrise-shell     isofiles/boot/
+cp target/i386-unknown-none-user/debug/sunrise-clock     isofiles/boot/
+cp target/i386-unknown-none-user/debug/sunrise-sm        isofiles/boot/
+cp target/i386-unknown-none-user/debug/sunrise-vi        isofiles/boot/
+cp target/i386-unknown-none-user/debug/sunrise-ahci      isofiles/boot/
 mkisofs-rs external/grub/isofiles isofiles -o os.iso -b boot/grub/i386-pc/eltorito.img --no-emul-boot --boot-info-table --embedded-boot external/grub/embedded.img
 '''
 ]
@@ -157,11 +153,11 @@ script = [
 '''
 cp target/i386-unknown-none/release/sunrise-bootstrap isofiles/boot/
 cp target/i386-unknown-none/release/sunrise-kernel    isofiles/boot/
-cp target/i386-unknown-none/release/sunrise-shell     isofiles/boot/
-cp target/i386-unknown-none/release/sunrise-clock     isofiles/boot/
-cp target/i386-unknown-none/release/sunrise-sm        isofiles/boot/
-cp target/i386-unknown-none/release/sunrise-vi        isofiles/boot/
-cp target/i386-unknown-none/release/sunrise-ahci      isofiles/boot/
+cp target/i386-unknown-none-user/release/sunrise-shell     isofiles/boot/
+cp target/i386-unknown-none-user/release/sunrise-clock     isofiles/boot/
+cp target/i386-unknown-none-user/release/sunrise-sm        isofiles/boot/
+cp target/i386-unknown-none-user/release/sunrise-vi        isofiles/boot/
+cp target/i386-unknown-none-user/release/sunrise-ahci      isofiles/boot/
 mkisofs-rs external/grub/isofiles isofiles -o os.iso -b boot/grub/i386-pc/eltorito.img --no-emul-boot --boot-info-table --embedded-boot external/grub/embedded.img
 '''
 ]

i386-unknown-none-user.json

@@ -0,0 +1,26 @@
+{
+  "llvm-target": "i386-unknown-none",
+  "data-layout": "e-m:e-p:32:32-f64:32:64-f80:32-n8:16:32-S128",
+  "arch": "x86",
+  "target-endian": "little",
+  "target-pointer-width": "32",
+  "target-c-int-width": "32",
+  "os": "none",
+  "linker": "rust-lld",
+  "linker-flavor": "ld.lld",
+  "linker-is-gnu": true,
+  "pre-link-args": {
+    "ld.lld": [
+      "-Tlinker-scripts/userspace.ld"
+    ]
+  },
+  "executables": true,
+  "env": "user",
+  "position-independent-executables": true,
+  "dynamic-linking": false,
+  "has-elf-tls": false,
+  "has-rpath": false,
+  "features": "-mmx,-sse,+soft-float",
+  "disable-redzone": true,
+  "panic-strategy": "abort"
+}

kernel/src/elf_loader.rs

@@ -107,7 +107,9 @@ pub fn load_builtin(process_memory: &mut ProcessMemory, module: &MappedGrubModul
     }
 
     // return the entry point
-    let entry_point = elf.header.pt2.entry_point();
+    // TODO: ASLR
+    // BODY: We should generate a random aslr base.
+    let entry_point = 0x400000 + elf.header.pt2.entry_point();
     info!("Entry point : {:#x?}", entry_point);
 
     entry_point as usize
@@ -133,8 +135,10 @@ fn load_segment(process_memory: &mut ProcessMemory, segment: ProgramHeader<'_>,
         flags |= MappingAccessRights::EXECUTABLE
     }
 
+    let virtual_addr = 0x400000 + segment.virtual_addr() as usize;
+
     // Create the mapping in UserLand
-    let userspace_addr = VirtualAddress(segment.virtual_addr() as usize);
+    let userspace_addr = VirtualAddress(virtual_addr);
     process_memory.create_regular_mapping(userspace_addr, mem_size_total, flags)
         .expect("Cannot load segment");
 
@@ -164,7 +168,7 @@ fn load_segment(process_memory: &mut ProcessMemory, segment: ProgramHeader<'_>,
     }
 
     info!("Loaded segment - VirtAddr {:#010x}, FileSize {:#010x}, MemSize {:#010x} {}{}{}",
-        segment.virtual_addr(), segment.file_size(), segment.mem_size(),
+        virtual_addr, segment.file_size(), segment.mem_size(),
         match segment.flags().is_read()    { true => 'R', false => ' '},
         match segment.flags().is_write()   { true => 'W', false => ' '},
         match segment.flags().is_execute() { true => 'X', false => ' '},

libuser/src/crt0/mod.rs

@@ -0,0 +1,63 @@
+//! libuser CRT0
+//! This module is a minimal RT0 handling the entry point of the application.
+//! It handles relocation, clean the bss and then finally call start_main.
+
+use core::ptr;
+
+mod relocation;
+
+/// Executable entrypoint. Handle relocations and calls real_start.
+#[cfg(target_os = "none")]
+#[naked]
+#[no_mangle]
+#[link_section = ".text.crt0"]
+pub unsafe extern fn start() {
+    asm!("
+    .intel_syntax noprefix
+    get_aslr_base:
+        call _start_shim
+    eip_pos:
+        .int module_header - get_aslr_base
+        // As x86 has variable instruction length, this is going to be the offset to the aslr base
+        .int eip_pos - get_aslr_base
+    _start_shim:
+        pop eax
+
+        // Save eip_pos address
+        mov ecx, eax
+
+        // Compute ASLR base because hey we don't have a choice
+        sub eax, [eax + 0x4]
+        mov ebx, eax
+
+        // Compute mod0 offset
+        add ebx, [ecx]
+
+        // Relocate the module
+        push ebx
+        push eax
+        call relocate_self
+
+        // Clean .bss
+        push ebx
+        call clean_bss
+
+        call real_start
+    ");
+}
+
+/// Clean module bss.
+/// NOTE: Even if the bss should be cleared before calling anything in Rust, all functions used here are guaranteed to not use the bss.
+#[cfg(target_os = "none")]
+#[no_mangle]
+#[link_section = ".text.crt0"]
+pub unsafe extern fn clean_bss(module_header: *const relocation::ModuleHeader) {
+    let module_header_address = module_header as *mut u8;
+    let module_header = &(*module_header);
+
+    let bss_start_address = module_header_address.add(module_header.bss_start_off as usize) as *mut u8;
+    let bss_end_address = module_header_address.add(module_header.bss_end_off as usize) as *mut u8;
+
+    let count = bss_end_address as usize - bss_start_address as usize;
+    ptr::write_bytes(bss_start_address, 0, count);
+}