From 4931a291f86410d5c43dd9471d23b7e890f91246 Mon Sep 17 00:00:00 2001
From: Jakub Konka <kubkon@jakubkonka.com>
Date: Sat, 20 Apr 2024 22:58:54 +0200
Subject: [PATCH] link/elf: keep track of sh_entsize per MergeSubsection

---
 src/link/Elf.zig               | 9 +++++++++
 src/link/Elf/Object.zig        | 1 +
 src/link/Elf/merge_section.zig | 1 +
 src/link/Elf/relocatable.zig   | 8 ++++++++
 4 files changed, 19 insertions(+)

diff --git a/src/link/Elf.zig b/src/link/Elf.zig
index 1677daa64f..5af7c7d6aa 100644
--- a/src/link/Elf.zig
+++ b/src/link/Elf.zig
@@ -3337,6 +3337,7 @@ pub fn addCommentString(self: *Elf) !void {
     msub.string_index = res.key.pos;
     msub.alignment = .@"1";
     msub.size = res.key.len;
+    msub.entsize = 1;
     msub.alive = true;
     res.sub.* = msub_index;
 }
@@ -3428,6 +3429,14 @@ fn initOutputSections(self: *Elf) !void {
             .flags = msec.flags,
         });
         msec.output_section_index = shndx;
+
+        var entsize = self.mergeSubsection(msec.subsections.items[0]).entsize;
+        for (msec.subsections.items) |index| {
+            const msub = self.mergeSubsection(index);
+            entsize = @min(entsize, msub.entsize);
+        }
+        const shdr = &self.shdrs.items[shndx];
+        shdr.sh_entsize = entsize;
     }
 }
 
diff --git a/src/link/Elf/Object.zig b/src/link/Elf/Object.zig
index f4aeb9b4c9..57531916eb 100644
--- a/src/link/Elf/Object.zig
+++ b/src/link/Elf/Object.zig
@@ -759,6 +759,7 @@ pub fn resolveMergeSubsections(self: *Object, elf_file: *Elf) !void {
                 msub.string_index = res.key.pos;
                 msub.alignment = atom_ptr.alignment;
                 msub.size = res.key.len;
+                msub.entsize = math.cast(u32, isec.sh_entsize) orelse return error.Overflow;
                 msub.alive = !elf_file.base.gc_sections or isec.sh_flags & elf.SHF_ALLOC == 0;
                 res.sub.* = msub_index;
             }
diff --git a/src/link/Elf/merge_section.zig b/src/link/Elf/merge_section.zig
index 50f4194f19..ab716794fc 100644
--- a/src/link/Elf/merge_section.zig
+++ b/src/link/Elf/merge_section.zig
@@ -168,6 +168,7 @@ pub const MergeSubsection = struct {
     string_index: u32 = 0,
     size: u32 = 0,
     alignment: Atom.Alignment = .@"1",
+    entsize: u32 = 0,
     alive: bool = false,
 
     pub fn address(msub: MergeSubsection, elf_file: *Elf) i64 {
diff --git a/src/link/Elf/relocatable.zig b/src/link/Elf/relocatable.zig
index eb8569d252..e1e87ce8af 100644
--- a/src/link/Elf/relocatable.zig
+++ b/src/link/Elf/relocatable.zig
@@ -289,6 +289,14 @@ fn initSections(elf_file: *Elf) !void {
             .flags = msec.flags,
         });
         msec.output_section_index = shndx;
+
+        var entsize = elf_file.mergeSubsection(msec.subsections.items[0]).entsize;
+        for (msec.subsections.items) |index| {
+            const msub = elf_file.mergeSubsection(index);
+            entsize = @min(entsize, msub.entsize);
+        }
+        const shdr = &elf_file.shdrs.items[shndx];
+        shdr.sh_entsize = entsize;
     }
 
     const needs_eh_frame = for (elf_file.objects.items) |index| {