From a6ab35353293531d1b04cc18b667729fd5ee280e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alex=20R=C3=B8nne=20Petersen?= <alex@alexrp.com>
Date: Tue, 26 May 2026 08:07:45 +0200
Subject: [PATCH] std.pie: add xtensa support

This might need more work to handle the DT_XTENSA_GOT_LOC_{OFF,SZ} insanity,
but this is at least a start.
---
 lib/std/pie.zig | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/lib/std/pie.zig b/lib/std/pie.zig
index 42bc64218116659d535e90802a458b90afc4658a..504bff815c7a1c55e25a3a4d9b8e700dbe338188 100644
--- a/lib/std/pie.zig
+++ b/lib/std/pie.zig
@@ -22,6 +22,7 @@ const R_RISCV_RELATIVE = 3;
 const R_390_RELATIVE = 12;
 const R_SH_RELATIVE = 165;
 const R_SPARC_RELATIVE = 22;
+const R_XTENSA_RELATIVE = 5;
 
 const R_RELATIVE = switch (builtin.cpu.arch) {
     .x86 => R_386_RELATIVE,
@@ -43,6 +44,7 @@ const R_RELATIVE = switch (builtin.cpu.arch) {
     .s390x => R_390_RELATIVE,
     .sh, .sheb => R_SH_RELATIVE,
     .sparc, .sparc64 => R_SPARC_RELATIVE,
+    .xtensa, .xtensaeb => R_XTENSA_RELATIVE,
     else => @compileError("Missing R_RELATIVE definition for this target"),
 };
 
@@ -261,6 +263,25 @@ inline fn getDynamicSymbol() [*]const elf.Dyn {
                 : [ret] "=r" (-> [*]const elf.Dyn),
                 :
                 : .{ .l7 = true }),
+            .xtensa, .xtensaeb => asm volatile (
+                \\ .weak _DYNAMIC
+                \\ .hidden _DYNAMIC
+                // Set things up such that after the `call0`, `a0` will point 1 byte before the
+                // embedded constant. Note that `call0` is a 3-byte instruction, so we need both
+                // `.balign` directives to be safe.
+                \\ .balign 4
+                \\ .begin no-transform
+                \\ call0 1f
+                \\ .end no-transform
+                \\ .balign 4
+                \\ .word _DYNAMIC - .
+                \\1:
+                \\ add a0, a0, 1
+                \\ l32i a8, a0, 0
+                \\ add %[ret], a0, a8
+                : [ret] "=a" (-> [*]const elf.Dyn),
+                :
+                : .{ .a0 = true, .a8 = true }),
             else => {
                 @compileError("PIE startup is not yet supported for this target!");
             },
-- 
2.54.0