linux-kernel - [PATCH] tools/x86/kcpuid: Dump the correct CPUID function in error

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Message-Id: <20230426094107.27348-1-bp@alien8.de>
Date:   Wed, 26 Apr 2023 11:41:07 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     X86 ML <x86@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] tools/x86/kcpuid: Dump the correct CPUID function in error

From: "Borislav Petkov (AMD)" <bp@...en8.de>

The tool uses the 16 least significant bits of the CPUID leaf as an
index into its array of CPUID function field descriptions.

However, when that index is non-existent, it uses the same, truncated
index to report it, which is wrong:

$ kcpuid -l 0x80000034
  ERR: invalid input index (0x34)

Use the original index number in the error message.

Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
---
 tools/arch/x86/kcpuid/kcpuid.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/tools/arch/x86/kcpuid/kcpuid.c b/tools/arch/x86/kcpuid/kcpuid.c
index 416f5b35dd8f..24b7d017ec2c 100644
--- a/tools/arch/x86/kcpuid/kcpuid.c
+++ b/tools/arch/x86/kcpuid/kcpuid.c
@@ -517,15 +517,16 @@ static void show_range(struct cpuid_range *range)
 static inline struct cpuid_func *index_to_func(u32 index)
 {
 	struct cpuid_range *range;
+	u32 func_idx;
 
 	range = (index & 0x80000000) ? leafs_ext : leafs_basic;
-	index &= 0x7FFFFFFF;
+	func_idx = index & 0xffff;
 
-	if (((index & 0xFFFF) + 1) > (u32)range->nr) {
+	if ((func_idx + 1) > (u32)range->nr) {
 		printf("ERR: invalid input index (0x%x)\n", index);
 		return NULL;
 	}
-	return &range->funcs[index];
+	return &range->funcs[func_idx];
 }
 
 static void show_info(void)
-- 
2.35.1