66 lines
2.3 KiB
Diff
66 lines
2.3 KiB
Diff
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diff --git a/arch/x86/include/asm/stackprotector.h b/arch/x86/include/asm/stackprotector.h
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index 91e29b6..9804a79 100644
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--- a/arch/x86/include/asm/stackprotector.h
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+++ b/arch/x86/include/asm/stackprotector.h
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@@ -55,8 +55,13 @@
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/*
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* Initialize the stackprotector canary value.
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*
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- * NOTE: this must only be called from functions that never return,
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+ * NOTE: this must only be called from functions that never return
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* and it must always be inlined.
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+ *
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+ * In addition, it should be called from a compilation unit for which
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+ * stack protector is disabled. Alternatively, the caller should not end
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+ * with a function call which gets tail-call optimized as that would
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+ * lead to checking a modified canary value.
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*/
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static __always_inline void boot_init_stack_canary(void)
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{
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diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
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index fe3ab96..4f275ac 100644
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--- a/arch/x86/kernel/smpboot.c
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+++ b/arch/x86/kernel/smpboot.c
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@@ -266,6 +266,14 @@ static void notrace start_secondary(void *unused)
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wmb();
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cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
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+
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+ /*
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+ * Prevent tail call to cpu_startup_entry() because the stack protector
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+ * guard has been changed a couple of function calls up, in
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+ * boot_init_stack_canary() and must not be checked before tail calling
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+ * another function.
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+ */
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+ prevent_tail_call_optimization();
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}
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/**
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diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
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index 8fb8a50..f2adb63 100644
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--- a/arch/x86/xen/smp_pv.c
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+++ b/arch/x86/xen/smp_pv.c
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@@ -93,6 +93,7 @@ asmlinkage __visible void cpu_bringup_and_idle(void)
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cpu_bringup();
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boot_init_stack_canary();
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cpu_startup_entry(CPUHP_AP_ONLINE_IDLE);
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+ prevent_tail_call_optimization();
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}
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void xen_smp_intr_free_pv(unsigned int cpu)
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diff --git a/include/linux/compiler.h b/include/linux/compiler.h
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index 034b0a6..732754d 100644
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--- a/include/linux/compiler.h
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+++ b/include/linux/compiler.h
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@@ -356,4 +356,10 @@ static inline void *offset_to_ptr(const int *off)
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/* &a[0] degrades to a pointer: a different type from an array */
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#define __must_be_array(a) BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
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+/*
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+ * This is needed in functions which generate the stack canary, see
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+ * arch/x86/kernel/smpboot.c::start_secondary() for an example.
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+ */
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+#define prevent_tail_call_optimization() asm("")
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+
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#endif /* __LINUX_COMPILER_H */
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