[PATCH v3 19/28] x86/xen: Make xen_start_kernel() noreturn
From: Josh Poimboeuf <jpoimboe@kernel.org>
Date: 2026-09-21 22:31:47
Also in:
lkml, rust-for-linux
Subsystem:
objtool, the rest, x86 architecture (32-bit and 64-bit), xen hypervisor x86 · Maintainers:
Josh Poimboeuf, Peter Zijlstra, Linus Torvalds, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen, Juergen Gross
startup_xen() calls xen_start_kernel() with the assumption that it never returns, otherwise it would fall off the end of SYM_CODE_END(), triggering undefined behavior. But startup_xen() actually can return if 'si' is NULL. That doesn't seem to be possible, so drop the check and mark xen_start_kernel() __noreturn. A NULL 'si' would now fault on the first xen_start_info dereference, which is at least a more deterministic way to crash. Now that the function can no longer return, objtool can derive its noreturn attribute directly and the noreturns.h entry can be removed. Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> --- arch/x86/xen/enlighten_pv.c | 5 +---- arch/x86/xen/xen-ops.h | 2 +- tools/objtool/noreturns.h | 1 - 3 files changed, 2 insertions(+), 6 deletions(-)
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 2c64b388f6164..8ec78df9d1d5b 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c@@ -1325,15 +1325,12 @@ static void __init xen_domu_set_legacy_features(void) extern void early_xen_iret_patch(void); /* First C function to be called on Xen boot */ -asmlinkage __visible void __init xen_start_kernel(struct start_info *si) +asmlinkage __visible void __init __noreturn xen_start_kernel(struct start_info *si) { struct physdev_set_iopl set_iopl; unsigned long initrd_start = 0; int rc; - if (!si) - return; - clear_bss(); xen_start_info = si;
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 47eebbb3684ab..d830807cfffca 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h@@ -73,7 +73,7 @@ void xen_force_evtchn_callback(void); void xen_pv_pre_suspend(void); void xen_pv_post_suspend(int suspend_cancelled); -void xen_start_kernel(struct start_info *si); +void __noreturn xen_start_kernel(struct start_info *si); void set_pte_mfn(unsigned long vaddr, unsigned long pfn, pgprot_t flags); void xen_init_mmu_ops(void);
diff --git a/tools/objtool/noreturns.h b/tools/objtool/noreturns.h
index 01c94f20d1818..c4b93fc6e6299 100644
--- a/tools/objtool/noreturns.h
+++ b/tools/objtool/noreturns.h@@ -21,4 +21,3 @@ NORETURN(panic) NORETURN(vpanic) NORETURN(rust_helper_BUG) NORETURN(sev_es_terminate) -NORETURN(xen_start_kernel)
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2.55.0