linux-hardening - [PATCH] kallsyms: Add more debug output for selftest

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Date:   Thu, 24 Aug 2023 13:58:00 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Luis Chamberlain <mcgrof@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>, Yonghong Song <yhs@...a.com>,
        "Erhard F." <erhard_f@...lbox.org>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        kernel test robot <oliver.sang@...el.com>,
        Petr Mladek <pmladek@...e.com>,
        Nicholas Piggin <npiggin@...il.com>,
        Yang Li <yang.lee@...ux.alibaba.com>,
        Vincenzo Palazzo <vincenzopalazzodev@...il.com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: [PATCH] kallsyms: Add more debug output for selftest

While debugging a recent kallsyms_selftest failure[1], I needed more
details on what specifically was failing. This adds those details for
each failure state that is checked.

[1] https://lore.kernel.org/all/202308232200.1c932a90-oliver.sang@intel.com/

Cc: Luis Chamberlain <mcgrof@...nel.org>
Cc: Yonghong Song <yhs@...a.com>
Cc: "Erhard F." <erhard_f@...lbox.org>
Cc: Zhen Lei <thunder.leizhen@...wei.com>
Cc: kernel test robot <oliver.sang@...el.com>
Cc: Petr Mladek <pmladek@...e.com>
Cc: Nicholas Piggin <npiggin@...il.com>
Cc: Yang Li <yang.lee@...ux.alibaba.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
---
 kernel/kallsyms_selftest.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/kernel/kallsyms_selftest.c b/kernel/kallsyms_selftest.c
index a2e3745d15c4..232e8faefb46 100644
--- a/kernel/kallsyms_selftest.c
+++ b/kernel/kallsyms_selftest.c
@@ -341,6 +341,7 @@ static int test_kallsyms_basic_function(void)
 		ret = lookup_symbol_name(addr, namebuf);
 		if (unlikely(ret)) {
 			namebuf[0] = 0;
+			pr_info("%d: lookup_symbol_name(%lx) failed\n", i, addr);
 			goto failed;
 		}
 
@@ -388,8 +389,11 @@ static int test_kallsyms_basic_function(void)
 			if (stat->addr != stat2->addr ||
 			    stat->real_cnt != stat2->real_cnt ||
 			    memcmp(stat->addrs, stat2->addrs,
-				   stat->save_cnt * sizeof(stat->addrs[0])))
+				   stat->save_cnt * sizeof(stat->addrs[0]))) {
+				pr_info("%s: mismatch between kallsyms_on_each_symbol() and kallsyms_on_each_match_symbol()\n",
+					namebuf);
 				goto failed;
+			}
 
 			/*
 			 * The average of random increments is 128, that is, one of
@@ -400,15 +404,23 @@ static int test_kallsyms_basic_function(void)
 		}
 
 		/* Need to be found at least once */
-		if (!stat->real_cnt)
+		if (!stat->real_cnt) {
+			pr_info("%s: Never found\n", namebuf);
 			goto failed;
+		}
 
 		/*
 		 * kallsyms_lookup_name() returns the address of the first
 		 * symbol found and cannot be NULL.
 		 */
-		if (!lookup_addr || lookup_addr != stat->addrs[0])
+		if (!lookup_addr) {
+			pr_info("%s: NULL lookup_addr?!\n", namebuf);
+			goto failed;
+		}
+		if (lookup_addr != stat->addrs[0]) {
+			pr_info("%s: lookup_addr != stat->addrs[0]\n", namebuf);
 			goto failed;
+		}
 
 		/*
 		 * If the addresses of all matching symbols are recorded, the
@@ -420,8 +432,10 @@ static int test_kallsyms_basic_function(void)
 					break;
 			}
 
-			if (j == stat->save_cnt)
+			if (j == stat->save_cnt) {
+				pr_info("%s: j == save_cnt?!\n", namebuf);
 				goto failed;
+			}
 		}
 	}
 
-- 
2.34.1