Stack unwinding support for cleaning up panicked tasks (#197)

* This is a major new feature that allows full and proper recovery from a panic. We now use DWARF debugging information to unwind a task's call stack upon panic. DWARF info is parsed from `.eh_frame` and `.gcc_except_table`.

* Use explicit address ranges in LoadedCrates and Sections, which is clearer and allows faster lockless searching.

* Add support for relocation type R_X86_64_PLT32, which is the same as R_X86_64_PC32.

applications/unwind_test/src/lib.rs

@@ -8,6 +8,7 @@ extern crate task;
 
 
 use alloc::vec::Vec;
+use alloc::boxed::Box;
 use alloc::string::String;
 
 
@@ -20,6 +21,10 @@ impl Drop for MyStruct {
 
 #[inline(never)]
 fn foo() {
+    let _res = task::set_my_panic_handler(Box::new(|info| {
+        info!("Unwind test caught panic at {}", info);
+    }));
+
     let _my_struct = MyStruct(10);
     panic!("intentional panic in unwind_test::foo()");
 }

book/src/ch00-00-introduction.md

@@ -30,7 +30,7 @@ One-line summaries of what each crate includes (may be incomplete):
 * `mod_mgmt`: Module management, including parsing, loading, linking, unloading, and metadata management.
 * `mouse`: simple PS2 mouse driver.
 * `nano-core`: a tiny module that is responsible for bootstrapping the OS at startup.
-* `panic_unwind`: Default entry point for panics and unwinding, as required by the Rust compiler.
+* `panic_entry`: Default entry point for panics and unwinding, as required by the Rust compiler.
 * `panic_wrapper`: Wrapper functions for handling and propagating panics.
 * `path`: contains functions for navigating the filesystem / getting pointers to specific directories via the Path struct 
 * `pci`: Basic PCI support for Theseus, x86 only.

cfg/x86_64-theseus.json

@@ -11,5 +11,5 @@
   "os": "none",
   "features": "-mmx,-sse,+soft-float",
   "disable-redzone": true,
-  "panic": "abort"
+  "panic": "unwind"
 }

kernel/_doc_root.rs

@@ -38,7 +38,7 @@
 //! * `mod_mgmt`: Module management, including parsing, loading, linking, unloading, and metadata management.
 //! * `mouse`: simple PS2 mouse driver.
 //! * `nano-core`: a tiny module that is responsible for bootstrapping the OS at startup.
-//! * `panic_unwind`: Default entry point for panics and unwinding, as required by the Rust compiler.
+//! * `panic_entry`: Default entry point for panics and unwinding, as required by the Rust compiler.
 //! * `panic_wrapper`: Wrapper functions for handling and propagating panics.
 //! * `path`: contains functions for navigating the filesystem / getting pointers to specific directories via the Path struct 
 //! * `pci`: Basic PCI support for Theseus, x86 only.

kernel/memory/src/paging/mapper.rs

@@ -489,7 +489,7 @@ impl MappedPages {
         let size_in_pages = self.size_in_pages();
 
         use paging::allocate_pages;
-        let new_pages = allocate_pages(self.size_in_pages()).ok_or_else(|| "Couldn't allocate_pages()")?;
+        let new_pages = allocate_pages(size_in_pages).ok_or_else(|| "Couldn't allocate_pages()")?;
 
         // we must temporarily map the new pages as Writable, since we're about to copy data into them
         let new_flags = new_flags.unwrap_or(self.flags);

kernel/mod_mgmt/Cargo.toml

@@ -14,10 +14,6 @@ qp-trie = "0.7.3"
 owning_ref = { git = "https://github.com/kevinaboos/owning-ref-rs" }
 cstr_core = "0.1.2"
 
-[dependencies.gimli]
-version = "0.19.0"
-default-features = false
-features = [ "read", "alloc" ]
 
 [dependencies.hashbrown]
 version = "0.1.8"