patch: explicit PROT_WRITE in zero_bss is redundant

Author: mikdusan

command/base

@@ -13,7 +13,7 @@ QEMU_REV="10.1.2"
 QEMU_GIT_COMMIT=""
 
 # reset to blank when QEMU_REV/GIT_COMMIT bumps, otherwise begin count from 1
-QEMU_REV_ZIG_SERIAL=1
+QEMU_REV_ZIG_SERIAL=2
 
 if [ -n "$QEMU_GIT_COMMIT" ]; then
     QEMU_SRC_BASENAME="${QEMU_NAME}-${QEMU_REV}-${QEMU_GIT_COMMIT}"

command/patch

@@ -10,3 +10,4 @@ RUN patch -p1 -i "${WORK_ROOT}/patch/linux-user__syscall.diff"
 RUN patch -p1 -i "${WORK_ROOT}/patch/linux-user__mlugg1.diff"
 RUN patch -p1 -i "${WORK_ROOT}/patch/linux-user__mlugg2.diff"
 RUN patch -p1 -i "${WORK_ROOT}/patch/linux-user__mlugg3.diff"
+RUN patch -p1 -i "${WORK_ROOT}/patch/linux-user__elfload.diff"

patch/linux-user__elfload.diff

@@ -0,0 +1,44 @@
+# From e9b300e1579d456fd307659f86d8ac0373a25fea Mon Sep 17 00:00:00 2001
+# From: David Rubin <david@vortan.dev>
+# Date: Wed, 5 Nov 2025 18:26:33 -0800
+# Subject: [PATCH] explicit `PROT_WRITE` in `zero_bss` is redundant
+#
+# The `PAGE_WRITE` check already protects the `memset`.
+#
+# The Zig compiler uses `memsz` to reserve virtual address
+# space that can be used by future updates, including
+# in non-writable sections such as `.text`.
+#
+# However, it also aligns `filesz` to the target page size,
+# so partial zeroing is never necassary for these incremental
+# binaries.
+#
+# When the host page size is larger than the target page
+# size, a single host page can represent multiple target pages.
+# `page_get_flags` takes this into account and merges the permissions
+# across the target pages. Therefore, if just one page in the
+# list of pages represented by a host page is writable, the
+# entire page must be writable.
+#
+# Every section is either entirely bss, thus already target page
+# aligned, or if partially aligned then the non-bss part will
+# have been writable (because it's a data section) and will cause
+# at least of part of the current host page to be writable.
+#
+diff --git a/linux-user/elfload.c b/linux-user/elfload.c
+index ea214105ff..bc529df298 100644
+--- a/linux-user/elfload.c
++++ b/linux-user/elfload.c
+@@ -2464,12 +2464,6 @@ static bool zero_bss(abi_ulong start_bss, abi_ulong end_bss,
+ {
+     abi_ulong align_bss;
+ 
+-    /* We only expect writable bss; the code segment shouldn't need this. */
+-    if (!(prot & PROT_WRITE)) {
+-        error_setg(errp, "PT_LOAD with non-writable bss");
+-        return false;
+-    }
+-
+     align_bss = TARGET_PAGE_ALIGN(start_bss);
+     end_bss = TARGET_PAGE_ALIGN(end_bss);
+