From 5baf0dcdaef4eefb32dbf9881150098b1233d782 Mon Sep 17 00:00:00 2001
From: Sean Cross <sean@xobs.io>
Date: Sat, 5 Aug 2023 20:44:54 +0800
Subject: [PATCH] find_fde: make `text_base` optional

No platforms currently use relative addressing. Make this parameter
optional in order to support targets where this value is not available.

Signed-off-by: Sean Cross <sean@xobs.io>
---
 src/unwinder/find_fde/custom.rs | 53 ++++++++++++++-------------------
 1 file changed, 23 insertions(+), 30 deletions(-)

diff --git a/src/unwinder/find_fde/custom.rs b/src/unwinder/find_fde/custom.rs
index cf9883d..7f89590 100644
--- a/src/unwinder/find_fde/custom.rs
+++ b/src/unwinder/find_fde/custom.rs
@@ -1,6 +1,7 @@
 use super::{FDEFinder, FDESearchResult};
 use crate::util::{deref_pointer, get_unlimited_slice};
 
+use core::num::NonZeroUsize;
 use core::sync::atomic::{AtomicU32, Ordering};
 use gimli::{BaseAddresses, EhFrame, EhFrameHdr, NativeEndian, UnwindSection};
 
@@ -22,7 +23,7 @@ pub unsafe trait EhFrameFinder {
 }
 
 pub struct FrameInfo {
-    pub text_base: usize,
+    pub text_base: Option<NonZeroUsize>,
     pub kind: FrameInfoKind,
 }
 
@@ -102,19 +103,18 @@ fn find_fde<T: EhFrameFinder + ?Sized>(eh_frame_finder: &T, pc: usize) -> Option
 
 fn find_fde_with_eh_frame_hdr(
     pc: usize,
-    text_base: usize,
+    text_base: Option<NonZeroUsize>,
     eh_frame_hdr: usize,
 ) -> Option<FDESearchResult> {
     unsafe {
-        let bases = BaseAddresses::default()
-            .set_text(text_base as _)
-            .set_eh_frame_hdr(eh_frame_hdr as _);
-        let eh_frame_hdr = EhFrameHdr::new(
-            get_unlimited_slice(eh_frame_hdr as usize as _),
-            NativeEndian,
-        )
-        .parse(&bases, core::mem::size_of::<usize>() as _)
-        .ok()?;
+        let mut bases = BaseAddresses::default().set_eh_frame_hdr(eh_frame_hdr as _);
+        if let Some(text_base) = text_base {
+            bases = bases.set_text(text_base.get() as _);
+        }
+        let eh_frame_hdr =
+            EhFrameHdr::new(get_unlimited_slice(eh_frame_hdr as usize as _), NativeEndian)
+                .parse(&bases, core::mem::size_of::<usize>() as _)
+                .ok()?;
         let eh_frame = deref_pointer(eh_frame_hdr.eh_frame_ptr());
         let bases = bases.set_eh_frame(eh_frame as _);
         let eh_frame = EhFrame::new(get_unlimited_slice(eh_frame as _), NativeEndian);
@@ -124,40 +124,33 @@ fn find_fde_with_eh_frame_hdr(
             if let Ok(fde) =
                 table.fde_for_address(&eh_frame, &bases, pc as _, EhFrame::cie_from_offset)
             {
-                return Some(FDESearchResult {
-                    fde,
-                    bases,
-                    eh_frame,
-                });
+                return Some(FDESearchResult { fde, bases, eh_frame });
             }
         }
 
         // Otherwise do the linear search.
         if let Ok(fde) = eh_frame.fde_for_address(&bases, pc as _, EhFrame::cie_from_offset) {
-            return Some(FDESearchResult {
-                fde,
-                bases,
-                eh_frame,
-            });
+            return Some(FDESearchResult { fde, bases, eh_frame });
         }
 
         None
     }
 }
 
-fn find_fde_with_eh_frame(pc: usize, text_base: usize, eh_frame: usize) -> Option<FDESearchResult> {
+fn find_fde_with_eh_frame(
+    pc: usize,
+    text_base: Option<NonZeroUsize>,
+    eh_frame: usize,
+) -> Option<FDESearchResult> {
     unsafe {
-        let bases = BaseAddresses::default()
-            .set_text(text_base as _)
-            .set_eh_frame(eh_frame as _);
+        let mut bases = BaseAddresses::default().set_eh_frame(eh_frame as _);
+        if let Some(text_base) = text_base {
+            bases = bases.set_text(text_base.get() as _);
+        }
         let eh_frame = EhFrame::new(get_unlimited_slice(eh_frame as _), NativeEndian);
 
         if let Ok(fde) = eh_frame.fde_for_address(&bases, pc as _, EhFrame::cie_from_offset) {
-            return Some(FDESearchResult {
-                fde,
-                bases,
-                eh_frame,
-            });
+            return Some(FDESearchResult { fde, bases, eh_frame });
         }
 
         None