Support external initramfs and custom cmdline

Complement the external kernel support added in the previous commits
with support for external initramfs and a custom kernel command line.

We don't have an immediate use case for this, as loading an external
initramfs may imply losing control of what's happening in the
guest, but it's a low-hanging fruit and may be useful for debugging or
a future use case.

Signed-off-by: Sergio Lopez <slp@redhat.com>

Author: slp

include/libkrun.h

@@ -423,7 +423,9 @@ int32_t krun_set_exec(uint32_t ctx_id,
  /* Supported disk image formats */
 int32_t krun_set_kernel(uint32_t ctx_id,
                         const char *kernel_path,
-                        uint32_t kernel_format);
+                        uint32_t kernel_format,
+                        const char *initramfs,
+                        const char *cmdline);
 
 /**
  * Sets environment variables to be configured in the context of the executable.

src/arch/src/aarch64/mod.rs

@@ -47,7 +47,10 @@ use crate::DeviceType;
 
 /// Returns a Vec of the valid memory addresses for aarch64.
 /// See [`layout`](layout) module for a drawing of the specific memory model for this platform.
-pub fn arch_memory_regions(size: usize) -> (ArchMemoryInfo, Vec<(GuestAddress, usize)>) {
+pub fn arch_memory_regions(
+    size: usize,
+    initrd_size: u64,
+) -> (ArchMemoryInfo, Vec<(GuestAddress, usize)>) {
     let page_size: usize = unsafe { libc::sysconf(libc::_SC_PAGESIZE).try_into().unwrap() };
     let dram_size = round_up(size, page_size);
     let ram_last_addr = layout::DRAM_MEM_START + (dram_size as u64);
@@ -57,6 +60,7 @@ pub fn arch_memory_regions(size: usize) -> (ArchMemoryInfo, Vec<(GuestAddress, u
         ram_last_addr,
         shm_start_addr,
         page_size,
+        initrd_addr: ram_last_addr - layout::FDT_MAX_SIZE as u64 - initrd_size,
     };
     let regions = if cfg!(feature = "efi") {
         vec![

src/arch/src/lib.rs

@@ -12,6 +12,7 @@ pub struct ArchMemoryInfo {
     pub ram_last_addr: u64,
     pub shm_start_addr: u64,
     pub page_size: usize,
+    pub initrd_addr: u64,
 }
 
 /// Module for aarch64 related functionality.

src/arch/src/x86_64/mod.rs

@@ -69,6 +69,7 @@ pub fn arch_memory_regions(
     size: usize,
     kernel_load_addr: Option<u64>,
     kernel_size: usize,
+    initrd_size: u64,
 ) -> (ArchMemoryInfo, Vec<(GuestAddress, usize)>) {
     let page_size: usize = unsafe { libc::sysconf(libc::_SC_PAGESIZE).try_into().unwrap() };
 
@@ -136,6 +137,7 @@ pub fn arch_memory_regions(
         ram_last_addr,
         shm_start_addr,
         page_size,
+        initrd_addr: ram_last_addr - initrd_size,
     };
     (info, regions)
 }
@@ -150,6 +152,7 @@ pub fn arch_memory_regions(
     size: usize,
     kernel_load_addr: Option<u64>,
     kernel_size: usize,
+    _initrd_size: u64,
 ) -> (ArchMemoryInfo, Vec<(GuestAddress, usize)>) {
     let page_size: usize = unsafe { libc::sysconf(libc::_SC_PAGESIZE).try_into().unwrap() };
 
@@ -195,6 +198,7 @@ pub fn arch_memory_regions(
         ram_last_addr,
         shm_start_addr,
         page_size,
+        initrd_addr: layout::INITRD_SEV_START,
     };
     (info, regions)
 }
@@ -342,7 +346,8 @@ mod tests {
 
     #[test]
     fn regions_lt_4gb() {
-        let (_info, regions) = arch_memory_regions(1usize << 29, KERNEL_LOAD_ADDR, KERNEL_SIZE);
+        let (_info, regions) =
+            arch_memory_regions(1usize << 29, Some(KERNEL_LOAD_ADDR), KERNEL_SIZE, 0);
         assert_eq!(2, regions.len());
         assert_eq!(GuestAddress(0), regions[0].0);
         assert_eq!(KERNEL_LOAD_ADDR as usize, regions[0].1);
@@ -355,8 +360,12 @@ mod tests {
 
     #[test]
     fn regions_gt_4gb() {
-        let (_info, regions) =
-            arch_memory_regions((1usize << 32) + 0x8000, KERNEL_LOAD_ADDR, KERNEL_SIZE);
+        let (_info, regions) = arch_memory_regions(
+            (1usize << 32) + 0x8000,
+            Some(KERNEL_LOAD_ADDR),
+            KERNEL_SIZE,
+            0,
+        );
         assert_eq!(3, regions.len());
         assert_eq!(GuestAddress(0), regions[0].0);
         assert_eq!(KERNEL_LOAD_ADDR as usize, regions[0].1);
@@ -383,21 +392,21 @@ mod tests {
         // Now assigning some memory that falls before the 32bit memory hole.
         let mem_size = 128 << 20;
         let (arch_mem_info, arch_mem_regions) =
-            arch_memory_regions(mem_size, KERNEL_LOAD_ADDR, KERNEL_SIZE);
+            arch_memory_regions(mem_size, Some(KERNEL_LOAD_ADDR), KERNEL_SIZE, 0);
         let gm = GuestMemoryMmap::from_ranges(&arch_mem_regions).unwrap();
         configure_system(&gm, &arch_mem_info, GuestAddress(0), 0, &None, no_vcpus).unwrap();
 
         // Now assigning some memory that is equal to the start of the 32bit memory hole.
         let mem_size = 3328 << 20;
         let (arch_mem_info, arch_mem_regions) =
-            arch_memory_regions(mem_size, KERNEL_LOAD_ADDR, KERNEL_SIZE);
+            arch_memory_regions(mem_size, Some(KERNEL_LOAD_ADDR), KERNEL_SIZE, 0);
         let gm = GuestMemoryMmap::from_ranges(&arch_mem_regions).unwrap();
         configure_system(&gm, &arch_mem_info, GuestAddress(0), 0, &None, no_vcpus).unwrap();
 
         // Now assigning some memory that falls after the 32bit memory hole.
         let mem_size = 3330 << 20;
         let (arch_mem_info, arch_mem_regions) =
-            arch_memory_regions(mem_size, KERNEL_LOAD_ADDR, KERNEL_SIZE);
+            arch_memory_regions(mem_size, Some(KERNEL_LOAD_ADDR), KERNEL_SIZE, 0);
         let gm = GuestMemoryMmap::from_ranges(&arch_mem_regions).unwrap();
         configure_system(&gm, &arch_mem_info, GuestAddress(0), 0, &None, no_vcpus).unwrap();
     }

src/libkrun/src/lib.rs

@@ -1034,7 +1034,7 @@ fn create_virtio_net(ctx_cfg: &mut ContextConfig, backend: VirtioNetBackend) {
 }
 
 #[cfg(all(target_arch = "x86_64", not(feature = "tee")))]
-fn map_kernel(ctx_id: u32, kernel_path: &str) -> i32 {
+fn map_kernel(ctx_id: u32, kernel_path: &PathBuf) -> i32 {
     let file = match File::options().read(true).write(false).open(kernel_path) {
         Ok(file) => file,
         Err(err) => {
@@ -1095,9 +1095,11 @@ pub unsafe extern "C" fn krun_set_kernel(
     ctx_id: u32,
     c_kernel_path: *const c_char,
     kernel_format: u32,
+    c_initramfs_path: *const c_char,
+    c_cmdline: *const c_char,
 ) -> i32 {
-    let kernel_path = match CStr::from_ptr(c_kernel_path).to_str() {
-        Ok(path) => path,
+    let path = match CStr::from_ptr(c_kernel_path).to_str() {
+        Ok(path) => PathBuf::from(path),
         Err(e) => {
             error!("Error parsing kernel_path: {:?}", e);
             return -libc::EINVAL;
@@ -1108,7 +1110,7 @@ pub unsafe extern "C" fn krun_set_kernel(
         // For raw kernels in x86_64, we map the kernel into the
         // process and treat it as a bundled kernel.
         #[cfg(all(target_arch = "x86_64", not(feature = "tee")))]
-        0 => return map_kernel(ctx_id, kernel_path),
+        0 => return map_kernel(ctx_id, path),
         #[cfg(target_arch = "aarch64")]
         0 => KernelFormat::Raw,
         1 => KernelFormat::Elf,
@@ -1121,9 +1123,46 @@ pub unsafe extern "C" fn krun_set_kernel(
         }
     };
 
+    let (initramfs_path, initramfs_size) = if !c_initramfs_path.is_null() {
+        match CStr::from_ptr(c_initramfs_path).to_str() {
+            Ok(path) => {
+                let path = PathBuf::from(path);
+                let size = match std::fs::metadata(&path) {
+                    Ok(metadata) => metadata.len(),
+                    Err(e) => {
+                        error!("Can't read initramfs metadata: {:?}", e);
+                        return -libc::EINVAL;
+                    }
+                };
+                (Some(path), size)
+            }
+            Err(e) => {
+                error!("Error parsing initramfs path: {:?}", e);
+                return -libc::EINVAL;
+            }
+        }
+    } else {
+        (None, 0)
+    };
+
+    let cmdline = if !c_cmdline.is_null() {
+        match CStr::from_ptr(c_cmdline).to_str() {
+            Ok(cmdline) => Some(cmdline.to_string()),
+            Err(e) => {
+                error!("Error parsing kernel cmdline: {:?}", e);
+                return -libc::EINVAL;
+            }
+        }
+    } else {
+        None
+    };
+
     let external_kernel = ExternalKernel {
-        path: PathBuf::from(kernel_path),
+        path,
         format,
+        initramfs_path,
+        initramfs_size,
+        cmdline,
     };
 
     match CTX_MAP.lock().unwrap().entry(ctx_id) {