genode/repos/base-sel4/patches/address_of_packed_member.patch

From 3e83f89990e356b02b227cd883d32ccafa283127 Mon Sep 17 00:00:00 2001
From: Simon Shields <simon.shields@data61.csiro.au>
Date: Tue, 17 Sep 2019 11:54:22 +1000
Subject: [PATCH] x86: avoid -Waddress-of-packed-member

It's safe to take the address of this member, since it's the
first thing in a cacheline-aligned struct.
---
 include/arch/x86/arch/32/mode/stack.h | 7 ++++++-
 src/arch/x86/kernel/vspace.c          | 9 +++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/include/arch/x86/arch/32/mode/stack.h b/include/arch/x86/arch/32/mode/stack.h
index 93304b96fa..e8e7f1c254 100644
--- src/kernel/sel4/include/arch/x86/arch/32/mode/stack.h
+++ src/kernel/sel4/include/arch/x86/arch/32/mode/stack.h
@@ -45,7 +45,12 @@ static inline void setKernelEntryStackPointer(tcb_t *target_thread)
     /* The first item to be pushed onto the stack should always be SS */
     register_context_top = (word_t)&target_thread->tcbArch.tcbContext.registers[SS + 1];
 
-    tss_ptr_set_esp0(&x86KSGlobalState[CURRENT_CPU_INDEX()].x86KStss.tss, register_context_top);
+    /*
+     * Work around -Waddress-of-packed-member. TSS is the first thing
+     * in the struct and so it's safe to take its address.
+     */
+    void *tss = &x86KSGlobalState[CURRENT_CPU_INDEX()].x86KStss.tss;
+    tss_ptr_set_esp0(tss, register_context_top);
 
     if (config_set(CONFIG_HARDWARE_DEBUG_API)) {
         x86_wrmsr(IA32_SYSENTER_ESP_MSR, register_context_top);
diff --git a/src/arch/x86/kernel/vspace.c b/src/arch/x86/kernel/vspace.c
index 0ff6d30fff..be9d5f6266 100644
--- src/kernel/sel4/src/arch/x86/kernel/vspace.c
+++ src/kernel/sel4/src/arch/x86/kernel/vspace.c
@@ -493,8 +493,13 @@ BOOT_CODE bool_t init_vm_state(void)
         SMP_COND_STATEMENT(return false);
     }
 
-    init_tss(&x86KSGlobalState[CURRENT_CPU_INDEX()].x86KStss.tss);
-    init_gdt(x86KSGlobalState[CURRENT_CPU_INDEX()].x86KSgdt, &x86KSGlobalState[CURRENT_CPU_INDEX()].x86KStss.tss);
+    /*
+     * Work around -Waddress-of-packed-member. TSS is the first thing
+     * in the struct and so it's safe to take its address.
+     */
+    void *tss_ptr = &x86KSGlobalState[CURRENT_CPU_INDEX()].x86KStss.tss;
+    init_tss(tss_ptr);
+    init_gdt(x86KSGlobalState[CURRENT_CPU_INDEX()].x86KSgdt, tss_ptr);
     init_idt(x86KSGlobalState[CURRENT_CPU_INDEX()].x86KSidt);
     return true;
 }