From 71dec251e3f15e198359498fab2a89369843a6c9 Mon Sep 17 00:00:00 2001
From: occheung <dc@m-labs.hk>
Date: Thu, 28 Nov 2024 16:39:58 +0800
Subject: [PATCH] ld/dwarf: remove reader resets

DWARF reader never had to reverse. Readers are already copied to achieve this effect.
Plus the position that it reverses to might be questionable.
---
 nac3ld/src/dwarf.rs | 29 +++++++++++------------------
 1 file changed, 11 insertions(+), 18 deletions(-)

diff --git a/nac3ld/src/dwarf.rs b/nac3ld/src/dwarf.rs
index 7feededc4..ece910b34 100644
--- a/nac3ld/src/dwarf.rs
+++ b/nac3ld/src/dwarf.rs
@@ -27,23 +27,16 @@ pub const DW_EH_PE_indirect: u8 = 0x80;
 pub struct DwarfReader<'a> {
     pub slice: &'a [u8],
     pub virt_addr: u32,
-    base_slice: &'a [u8],
-    base_virt_addr: u32,
 }
 
 impl<'a> DwarfReader<'a> {
     pub fn new(slice: &[u8], virt_addr: u32) -> DwarfReader {
-        DwarfReader { slice, virt_addr, base_slice: slice, base_virt_addr: virt_addr }
+        DwarfReader { slice, virt_addr }
     }
 
-    /// Creates a new instance from another instance of [DwarfReader], optionally removing any
-    /// offsets previously applied to the other instance.
-    pub fn from_reader(other: &DwarfReader<'a>, reset_offset: bool) -> DwarfReader<'a> {
-        if reset_offset {
-            DwarfReader::new(other.base_slice, other.base_virt_addr)
-        } else {
-            DwarfReader::new(other.slice, other.virt_addr)
-        }
+    /// Creates a new instance from another instance of [DwarfReader].
+    pub fn from_reader(other: &DwarfReader<'a>) -> DwarfReader<'a> {
+        DwarfReader::new(other.slice, other.virt_addr)
     }
 
     pub fn offset(&mut self, offset: u32) {
@@ -228,7 +221,7 @@ impl<'a> EH_Frame<'a> {
 
     /// Returns an [Iterator] over all Call Frame Information (CFI) records.
     pub fn cfi_records(&self) -> CFI_Records<'a> {
-        let reader = DwarfReader::from_reader(&self.reader, true);
+        let reader = DwarfReader::from_reader(&self.reader);
         let len = reader.slice.len();
 
         CFI_Records { reader, available: len }
@@ -259,7 +252,7 @@ impl<'a> CFI_Record<'a> {
             0xFFFF_FFFF => unimplemented!(),
 
             _ => {
-                let mut fde_reader = DwarfReader::from_reader(cie_reader, false);
+                let mut fde_reader = DwarfReader::from_reader(cie_reader);
                 fde_reader.offset(length);
                 fde_reader
             }
@@ -278,7 +271,7 @@ impl<'a> CFI_Record<'a> {
         // Skip code/data alignment factors & return address register along the way as well
         // We only tackle the case where 'z' and 'R' are part of the augmentation string, otherwise
         // we cannot get the addresses to make .eh_frame_hdr
-        let mut aug_data_reader = DwarfReader::from_reader(cie_reader, false);
+        let mut aug_data_reader = DwarfReader::from_reader(cie_reader);
         let mut aug_str_len = 0;
         loop {
             if aug_data_reader.read_u8() == b'\0' {
@@ -321,7 +314,7 @@ impl<'a> CFI_Record<'a> {
     /// Returns a [DwarfReader] initialized to the first Frame Description Entry (FDE) of this CFI
     /// record.
     pub fn get_fde_reader(&self) -> DwarfReader<'a> {
-        DwarfReader::from_reader(&self.fde_reader, false)
+        DwarfReader::from_reader(&self.fde_reader)
     }
 
     /// Returns an [Iterator] over all Frame Description Entries (FDEs).
@@ -349,7 +342,7 @@ impl<'a> Iterator for CFI_Records<'a> {
                 return None;
             }
 
-            let mut this_reader = DwarfReader::from_reader(&self.reader, false);
+            let mut this_reader = DwarfReader::from_reader(&self.reader);
 
             // Remove the length of the header and the content from the counter
             let length = self.reader.read_u32();
@@ -362,7 +355,7 @@ impl<'a> Iterator for CFI_Records<'a> {
 
             // Remove the length of the header and the content from the counter
             self.available -= length + mem::size_of::<u32>();
-            let mut next_reader = DwarfReader::from_reader(&self.reader, false);
+            let mut next_reader = DwarfReader::from_reader(&self.reader);
             next_reader.offset(length as u32);
 
             let cie_ptr = self.reader.read_u32();
@@ -410,7 +403,7 @@ impl<'a> Iterator for FDE_Records<'a> {
 
         // Remove the length of the header and the content from the counter
         self.available -= length + mem::size_of::<u32>();
-        let mut next_fde_reader = DwarfReader::from_reader(&self.reader, false);
+        let mut next_fde_reader = DwarfReader::from_reader(&self.reader);
         next_fde_reader.offset(length as u32);
 
         let cie_ptr = self.reader.read_u32();