[PATCH] kallsyms: Add more debug output for selftest

[PATCH] kallsyms: Add more debug output for selftest

[Kees Cook]

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@kernel.org>
Cc: Yonghong Song <yhs@meta.com>
Cc: "Erhard F." <erhard_f@mailbox.org>
Cc: Zhen Lei <thunder.leizhen@huawei.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Kees Cook <keescook@chromium.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

Re: [PATCH] kallsyms: Add more debug output for selftest

[Luis Chamberlain]

On Thu, Aug 24, 2023 at 01:58:00PM -0700, Kees Cook wrote:
> 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@kernel.org>
> Cc: Yonghong Song <yhs@meta.com>
> Cc: "Erhard F." <erhard_f@mailbox.org>
> Cc: Zhen Lei <thunder.leizhen@huawei.com>
> Cc: kernel test robot <oliver.sang@intel.com>
> Cc: Petr Mladek <pmladek@suse.com>
> Cc: Nicholas Piggin <npiggin@gmail.com>
> Cc: Yang Li <yang.lee@linux.alibaba.com>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Applied and pushed, thanks.

  Luis