fw_meta: refactor parse_fw_meta_data() to take a VirtAddr

Refactor the public function parse_fw_meta_data() so that the caller can provide an arbitrary address where the firmware starts. This will help building a fuzzing harness around this interface. Signed-off-by: Carlos López <[email protected]>
00xc · Oct 11, 2023 · 38e41aa · 38e41aa
1 parent c1aa81b
commit 38e41aa
Show file tree

Hide file tree

Showing 2 changed files with 15 additions and 11 deletions.
diff --git a/src/fw_meta.rs b/src/fw_meta.rs
@@ -6,11 +6,10 @@
 
 extern crate alloc;
 
-use crate::address::{Address, PhysAddr};
+use crate::address::{Address, PhysAddr, VirtAddr};
 use crate::cpu::percpu::this_cpu_mut;
 use crate::error::SvsmError;
 use crate::mm::PerCPUPageMappingGuard;
-use crate::mm::SIZE_1G;
 use crate::sev::ghcb::PageStateChangeOp;
 use crate::sev::{pvalidate, rmp_adjust, PvalidateOp, RMPFlags};
 use crate::types::{PageSize, PAGE_SIZE};
@@ -245,15 +244,12 @@ fn find_table<'a>(uuid: &Uuid, mem: &'a [u8]) -> Option<&'a [u8]> {
     None
 }
 
-pub fn parse_fw_meta_data() -> Result<SevFWMetaData, SvsmError> {
+/// Parse the firmware metadata located at the memory page starting at `vstart`.
+pub fn parse_fw_meta_data(vstart: VirtAddr) -> Result<SevFWMetaData, SvsmError> {
     let mut meta_data = SevFWMetaData::new();
-    // Map meta-data location, it starts at 32 bytes below 4GiB
-    let pstart = PhysAddr::from((4 * SIZE_1G) - PAGE_SIZE);
-    let guard = PerCPUPageMappingGuard::create_4k(pstart)?;
-    let vstart = guard.virt_addr();
 
-    // Safety: RawMetaBuffer has a size of one page and it has no invalid
-    // representations.
+    // Safety: the caller must guarantee that the region starting at `vstart`
+    // has a size of one page. `RawMetaBuffer` has no invalid representations.
     let raw_meta = unsafe { &*vstart.as_ptr::<RawMetaBuffer>() };
 
     // Check the UUID

diff --git a/src/svsm.rs b/src/svsm.rs
@@ -37,7 +37,7 @@ use svsm::mm::alloc::{memory_info, print_memory_info, root_mem_init};
 use svsm::mm::memory::init_memory_map;
 use svsm::mm::pagetable::paging_init;
 use svsm::mm::virtualrange::virt_log_usage;
-use svsm::mm::{init_kernel_mapping_info, PerCPUPageMappingGuard};
+use svsm::mm::{init_kernel_mapping_info, PerCPUPageMappingGuard, SIZE_1G};
 use svsm::requests::{request_loop, update_mappings};
 use svsm::serial::SerialPort;
 use svsm::serial::SERIAL_PORT;
@@ -310,6 +310,14 @@ fn mapping_info_init(launch_info: &KernelLaunchInfo) {
     );
 }
 
+fn map_and_parse_fw_meta() -> Result<SevFWMetaData, SvsmError> {
+    // Map meta-data location, it starts at 32 bytes below 4GiB
+    let pstart = PhysAddr::from((4 * SIZE_1G) - PAGE_SIZE);
+    let guard = PerCPUPageMappingGuard::create_4k(pstart)?;
+    let vstart = guard.virt_addr();
+    parse_fw_meta_data(vstart)
+}
+
 #[no_mangle]
 pub extern "C" fn svsm_start(li: &KernelLaunchInfo, vb_addr: usize) {
     let launch_info: KernelLaunchInfo = *li;
@@ -445,7 +453,7 @@ pub extern "C" fn svsm_main() {
 
     start_secondary_cpus(&cpus);
 
-    let fw_meta = parse_fw_meta_data()
+    let fw_meta = map_and_parse_fw_meta()
         .unwrap_or_else(|e| panic!("Failed to parse FW SEV meta-data: {:#?}", e));
 
     print_fw_meta(&fw_meta);