x86: Convert unreachable() to BUG()

[tip: objtool/core] x86: Convert unreachable() to BUG()

Posted by tip-bot2 for Peter Zijlstra 1 year, 2 months ago

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     2190966fbc14ca2cd4ea76eefeb96a47d8e390df
Gitweb:        https://git.kernel.org/tip/2190966fbc14ca2cd4ea76eefeb96a47d8e390df
Author:        Peter Zijlstra <peterz@infradead.org>
AuthorDate:    Thu, 28 Nov 2024 10:39:02 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Mon, 02 Dec 2024 12:01:43 +01:00

x86: Convert unreachable() to BUG()

Avoid unreachable() as it can (and will in the absence of UBSAN)
generate fallthrough code. Use BUG() so we get a UD2 trap (with
unreachable annotation).

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20241128094312.028316261@infradead.org
---
 arch/x86/kernel/process.c | 2 +-
 arch/x86/kernel/reboot.c  | 2 +-
 arch/x86/kvm/svm/sev.c    | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index f63f8fd..15507e7 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -838,7 +838,7 @@ void __noreturn stop_this_cpu(void *dummy)
 #ifdef CONFIG_SMP
 	if (smp_ops.stop_this_cpu) {
 		smp_ops.stop_this_cpu();
-		unreachable();
+		BUG();
 	}
 #endif
 
diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
index 6159228..dc1dd3f 100644
--- a/arch/x86/kernel/reboot.c
+++ b/arch/x86/kernel/reboot.c
@@ -883,7 +883,7 @@ static int crash_nmi_callback(unsigned int val, struct pt_regs *regs)
 
 	if (smp_ops.stop_this_cpu) {
 		smp_ops.stop_this_cpu();
-		unreachable();
+		BUG();
 	}
 
 	/* Assume hlt works */
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 943bd07..fe6cc76 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3820,7 +3820,7 @@ next_range:
 		goto next_range;
 	}
 
-	unreachable();
+	BUG();
 }
 
 static int __sev_snp_update_protected_guest_state(struct kvm_vcpu *vcpu)

Re: [tip: objtool/core] x86: Convert unreachable() to BUG()

Posted by Peter Zijlstra 1 year, 1 month ago

On Mon, Dec 02, 2024 at 11:15:21AM -0000, tip-bot2 for Peter Zijlstra wrote:
> The following commit has been merged into the objtool/core branch of tip:
> 
> Commit-ID:     2190966fbc14ca2cd4ea76eefeb96a47d8e390df
> Gitweb:        https://git.kernel.org/tip/2190966fbc14ca2cd4ea76eefeb96a47d8e390df
> Author:        Peter Zijlstra <peterz@infradead.org>
> AuthorDate:    Thu, 28 Nov 2024 10:39:02 +01:00
> Committer:     Peter Zijlstra <peterz@infradead.org>
> CommitterDate: Mon, 02 Dec 2024 12:01:43 +01:00
> 
> x86: Convert unreachable() to BUG()
> 
> Avoid unreachable() as it can (and will in the absence of UBSAN)
> generate fallthrough code. Use BUG() so we get a UD2 trap (with
> unreachable annotation).
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
> Link: https://lore.kernel.org/r/20241128094312.028316261@infradead.org


Urgh, one got lost:

vmlinux.o: warning: objtool: page_fault_oops() falls through to next function is_prefetch()

---
 arch/x86/mm/fault.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e6c469b323cc..ac52255fab01 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -678,7 +678,7 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
 			      ASM_CALL_ARG3,
 			      , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
 
-		unreachable();
+		BUG();
 	}
 #endif

[tip: objtool/core] x86/mm: Convert unreachable() to BUG()

Posted by tip-bot2 for Peter Zijlstra 1 year, 1 month ago

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     41a1e976623eb430f7b5a8619d3810b44e6235ad
Gitweb:        https://git.kernel.org/tip/41a1e976623eb430f7b5a8619d3810b44e6235ad
Author:        Peter Zijlstra <peterz@infradead.org>
AuthorDate:    Mon, 16 Dec 2024 11:08:12 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 17 Dec 2024 17:47:21 +01:00

x86/mm: Convert unreachable() to BUG()

Commit 2190966fbc14 ("x86: Convert unreachable() to BUG()") missed
one.

And after commit 06e24745985c ("objtool: Remove
annotate_{,un}reachable()") the invalid use of unreachable()
(rightfully) triggers warnings:

  vmlinux.o: warning: objtool: page_fault_oops() falls through to next function is_prefetch()

Fixes: 2190966fbc14 ("x86: Convert unreachable() to BUG()")
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20241216093215.GD12338@noisy.programming.kicks-ass.net
---
 arch/x86/mm/fault.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index e6c469b..ac52255 100644
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -678,7 +678,7 @@ page_fault_oops(struct pt_regs *regs, unsigned long error_code,
 			      ASM_CALL_ARG3,
 			      , [arg1] "r" (regs), [arg2] "r" (address), [arg3] "r" (&info));
 
-		unreachable();
+		BUG();
 	}
 #endif