Merge pull request #18 from philipc/eh_frame_size

Try to determine the size of the eh_frame section

Author: main--

unwind/src/find_cfi/baremetal.rs

@@ -6,6 +6,7 @@ extern "C" {
     static __text_end: usize;
     static __ehframehdr_start: usize;
     static __ehframehdr_end: usize;
+    static __ehframe_end: usize;
 }
 
 pub fn find_cfi_sections() -> Vec<EhRef> {
@@ -17,11 +18,13 @@ pub fn find_cfi_sections() -> Vec<EhRef> {
         let text_end = &__text_end as *const _ as u64;
         let cfi_start = &__ehframehdr_start as *const _ as u64;
         let cfi_end = &__ehframehdr_end as *const _ as u64;
+        let eh_frame_end = &__ehframe_end as *const _ as u64;
 
         cfi.push(EhRef {
             obj_base: 0,
             text: AddrRange { start: text_start, end: text_end },
             cfi: AddrRange { start: cfi_start, end: cfi_end },
+            ehframe_end,
         });
     }
     trace!("CFI sections: {:?}", cfi);

unwind/src/find_cfi/ld.rs

@@ -1,6 +1,6 @@
 use libc::{c_void, c_int, c_char};
 use std::ffi::CStr;
-use std::{slice, mem};
+use std::{slice, mem, cmp};
 use range::AddrRange;
 use super::EhRef;
 
@@ -60,10 +60,15 @@ extern "C" fn callback(info: *const DlPhdrInfo, size: usize, data: *mut c_void)
             if let Some(eh_frame) = phdr.iter().filter(|x| x.type_ == PT_GNU_EH_FRAME).next() {
                 let start_addr = (*info).addr + text.vaddr;
                 let cfi_start = (*info).addr + eh_frame.vaddr;
+                let max_vaddr = phdr.iter().filter(|x| x.type_ == PT_LOAD)
+                    .fold(0, |vaddr, x| cmp::max(vaddr, x.vaddr + x.memsz));
+                // This is an upper bound, not the exact address.
+                let ehframe_end = (*info).addr + max_vaddr;
                 (*data).push(EhRef {
                     obj_base: (*info).addr,
                     text: AddrRange { start: start_addr, end: start_addr + text.memsz },
                     cfi: AddrRange { start: cfi_start, end: cfi_start + eh_frame.memsz },
+                    ehframe_end,
                 });
             }
         }

unwind/src/find_cfi/mod.rs

@@ -5,6 +5,7 @@ pub struct EhRef {
     pub obj_base: u64,
     pub text: AddrRange,
     pub cfi: AddrRange,
+    pub ehframe_end: u64,
 }
 
 #[cfg(unix)]

unwind/src/lib.rs

@@ -60,7 +60,7 @@ impl Default for DwarfUnwinder {
                 let eh_frame_hdr = EhFrameHdr::new(eh_frame_hdr, NativeEndian).parse(&bases, 8).unwrap();
 
                 let cfi_addr = deref_ptr(eh_frame_hdr.eh_frame_ptr());
-                let cfi_sz = 0x10000000; // FIXME HACK
+                let cfi_sz = er.ehframe_end.saturating_sub(cfi_addr);
 
                 let eh_frame: &'static [u8] = std::slice::from_raw_parts(cfi_addr as *const u8, cfi_sz as usize);
                 trace!("cfi at {:p} sz {:x}", cfi_addr as *const u8, cfi_sz);