[tip: x86/misc] x86/ia32: State that IA32 emulation is disabled

[tip-bot2 for Borislav Petkov (AMD)]

The following commit has been merged into the x86/misc branch of tip:

Commit-ID:     f789383fa34a266d0c1a76f272043a15a8edf733
Gitweb:        https://git.kernel.org/tip/f789383fa34a266d0c1a76f272043a15a8edf733
Author:        Borislav Petkov (AMD) <bp@xxxxxxxxx>
AuthorDate:    Thu, 30 Nov 2023 16:39:33 +01:00
Committer:     Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Mon, 11 Dec 2023 10:14:28 +01:00

x86/ia32: State that IA32 emulation is disabled

Issue a short message once, on the first try to load a 32-bit process to
save people time when wondering why it won't load and trying to execute
it, would say:

  -bash: ./strsep32: cannot execute binary file: Exec format error

Signed-off-by: Borislav Petkov (AMD) <bp@xxxxxxxxx>
Reviewed-by: Nikolay Borisov <nik.borisov@xxxxxxxx>
Link: https://lore.kernel.org/r/20231130155213.1407-1-bp@xxxxxxxxx
---
 arch/x86/include/asm/elf.h  |  2 +-
 arch/x86/include/asm/ia32.h | 11 ++++++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/elf.h b/arch/x86/include/asm/elf.h
index a0234df..1e16bd5 100644
--- a/arch/x86/include/asm/elf.h
+++ b/arch/x86/include/asm/elf.h
@@ -150,7 +150,7 @@ do {						\
 	((x)->e_machine == EM_X86_64)
 
 #define compat_elf_check_arch(x)					\
-	((elf_check_arch_ia32(x) && ia32_enabled()) ||			\
+	((elf_check_arch_ia32(x) && ia32_enabled_verbose()) ||		\
 	 (IS_ENABLED(CONFIG_X86_X32_ABI) && (x)->e_machine == EM_X86_64))
 
 static inline void elf_common_init(struct thread_struct *t,
diff --git a/arch/x86/include/asm/ia32.h b/arch/x86/include/asm/ia32.h
index 5a2ae24..094886a 100644
--- a/arch/x86/include/asm/ia32.h
+++ b/arch/x86/include/asm/ia32.h
@@ -2,7 +2,6 @@
 #ifndef _ASM_X86_IA32_H
 #define _ASM_X86_IA32_H
 
-
 #ifdef CONFIG_IA32_EMULATION
 
 #include <linux/compat.h>
@@ -84,4 +83,14 @@ static inline bool ia32_enabled(void)
 
 #endif
 
+static inline bool ia32_enabled_verbose(void)
+{
+	bool enabled = ia32_enabled();
+
+	if (IS_ENABLED(CONFIG_IA32_EMULATION) && !enabled)
+		pr_notice_once("32-bit emulation disabled. You can reenable with ia32_emulation=on\n");
+
+	return enabled;
+}
+
 #endif /* _ASM_X86_IA32_H */