From 8161e61548135dcbc2c3563a61b75c08c8f7cb2c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Fri, 26 Jul 2024 01:07:34 +0200
Subject: [PATCH] std.os.linux.start_pie: Add support for the new RELR
 relocation format.

---
 lib/std/os/linux/start_pie.zig | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/lib/std/os/linux/start_pie.zig b/lib/std/os/linux/start_pie.zig
index dbe3f5565e..5099f39563 100644
--- a/lib/std/os/linux/start_pie.zig
+++ b/lib/std/os/linux/start_pie.zig
@@ -277,4 +277,28 @@ pub fn relocate(phdrs: []elf.Phdr) void {
             @as(*usize, @ptrFromInt(base_addr + r.r_offset)).* = base_addr + @as(usize, @bitCast(r.r_addend));
         }
     }
+
+    const relr = sorted_dynv[elf.DT_RELR];
+    if (relr != 0) {
+        const relrs = @call(.always_inline, std.mem.bytesAsSlice, .{
+            elf.Relr,
+            @as([*]u8, @ptrFromInt(base_addr + relr))[0..sorted_dynv[elf.DT_RELRSZ]],
+        });
+        var current: [*]usize = undefined;
+        for (relrs) |r| {
+            if ((r & 1) == 0) {
+                current = @ptrFromInt(base_addr + r);
+                current[0] += base_addr;
+                current += 1;
+            } else {
+                // Skip the first bit; there are 63 locations in the bitmap.
+                var i: if (@sizeOf(usize) == 8) u6 else u5 = 1;
+                while (i < @bitSizeOf(elf.Relr)) : (i += 1) {
+                    if (((r >> i) & 1) != 0) current[i] += base_addr;
+                }
+
+                current += @bitSizeOf(elf.Relr) - 1;
+            }
+        }
+    }
 }