[PATCH v7] shmctl03: Fix 32-bit compat mode failure by adjusting comparisons for compat mode truncation

On 64-bit kernels, the default shmmax and shmall values often exceed
the range of a 32-bit unsigned long or are clipped differently by the
kernel's compat syscall layer than they appear in /proc.

Link: https://lore.kernel.org/ltp/[email protected]/
Signed-off-by: Wei Gao <wegao-IBi9RG/[email protected]>
Suggested-by: Cyril Hrubis <[email protected]>
Reviewed-by: Andrea Cervesato <andrea.cervesato-IBi9RG/[email protected]>
Reported-by: Dan Carpenter <[email protected]>
---
v6->v7:
- kernel-doc for tst_assert_ulong

 include/tst_assert.h                        | 42 ++++++++++++++++++---
 lib/tst_assert.c                            | 27 ++++++++++---
 testcases/kernel/syscalls/shmctl/shmctl03.c | 17 +++++++--
 3 files changed, 72 insertions(+), 14 deletions(-)

diff --git a/include/tst_assert.h b/include/tst_assert.h
index dcb62dfea..3cc0d334d 100644
--- a/include/tst_assert.h
+++ b/include/tst_assert.h
@@ -21,14 +21,46 @@ void tst_assert_int(const char *file, const int lineno,
 #define TST_ASSERT_FILE_INT(path, prefix, val) \
 	tst_assert_file_int(__FILE__, __LINE__, path, prefix, val)
 
-/*
- * Same as tst_assert_int() but for unsigned long.
+/**
+ * TST_ASSERT_SATURATED_INT - Clamp the sysfs/procfs value to INT_MAX.
+ *
+ * If this flag is set and the value read from the sysfs/procfs file exceeds
+ * INT_MAX, the compared value is clamped (saturated) to INT_MAX.
+ */
+#define TST_ASSERT_SATURATED_INT   0x01
+
+/**
+ * TST_ASSERT_BITWISE - Keep only the lower 32 bits of the read value.
+ *
+ * If this flag is set, only the low 32 bits of the value read from the
+ * sysfs/procfs file are compared.
+ */
+#define TST_ASSERT_BITWISE         0x02
+
+/**
+ * tst_assert_ulong() - Assert that an unsigned long value in a file matches.
+ * @file: The source file of the assertion (usually __FILE__).
+ * @lineno: The source line number of the assertion (usually __LINE__).
+ * @path: Path to the sysfs or procfs file to read from.
+ * @val: The expected unsigned long value to compare against.
+ * @flags: Bitwise flags controlling how the read value is processed.
+ *         Supported flags:
+ *         - %TST_ASSERT_SATURATED_INT: Clamps the value at %INT_MAX if it
+ *           exceeds it.
+ *         - %TST_ASSERT_BITWISE: Keeps only the low 32 bits of the read value,
+ *           truncating any higher bits.
+ *         - %0: Direct comparison without any adjustment.
+ *
+ * This function reads an integer value from the file specified by @path and compares
+ * it with @val. It allows handling of 32-bit compat mode truncation/clamping on
+ * 64-bit systems via @flags.
  */
 void tst_assert_ulong(const char *file, const int lineno,
-                      const char *path, unsigned long val);
+                      const char *path, unsigned long val, int flags);
 
-#define TST_ASSERT_ULONG(path, val) \
-	tst_assert_ulong(__FILE__, __LINE__, path, val)
+#define TST_ASSERT_ULONG(path, val, ...) \
+	tst_assert_ulong(__FILE__, __LINE__, path, val, \
+		TST_2_(dummy, ##__VA_ARGS__, 0))
 
 /*
  * Asserts that integer value stored in the prefix field of file pointed by path
diff --git a/lib/tst_assert.c b/lib/tst_assert.c
index b68bd5d39..fd651f53a 100644
--- a/lib/tst_assert.c
+++ b/lib/tst_assert.c
@@ -5,6 +5,7 @@
  * Copyright (c) 2020 Cyril Hrubis <[email protected]>
  */
 #include <stdio.h>
+#include <limits.h>
 #define TST_NO_DEFAULT_MAIN
 #include "tst_assert.h"
 #include "tst_test.h"
@@ -23,18 +24,32 @@ void tst_assert_int(const char *file, const int lineno, const char *path, int va
 	tst_res_(file, lineno, TFAIL, "%s != %d got %d", path, val, sys_val);
 }
 
-void tst_assert_ulong(const char *file, const int lineno, const char *path, unsigned long val)
+void tst_assert_ulong(const char *file, const int lineno, const char *path,
+		      unsigned long val, int flags)
 {
-	unsigned long sys_val;
-
-	safe_file_scanf(file, lineno, NULL, path, "%lu", &sys_val);
+	unsigned long long sys_val_64;
+	unsigned long expected_val;
+
+	safe_file_scanf(file, lineno, NULL, path, "%llu", &sys_val_64);
+
+	if (flags & TST_ASSERT_SATURATED_INT) {
+		if (sys_val_64 > (unsigned long long)INT_MAX)
+			expected_val = (unsigned long)INT_MAX;
+		else
+			expected_val = (unsigned long)sys_val_64;
+	} else if (flags & TST_ASSERT_BITWISE) {
+		expected_val = (unsigned long)(sys_val_64 & 0xFFFFFFFFULL);
+	} else {
+		expected_val = (unsigned long)sys_val_64;
+	}
 
-	if (val == sys_val) {
+	if (val == expected_val) {
 		tst_res_(file, lineno, TPASS, "%s = %lu", path, val);
 		return;
 	}
 
-	tst_res_(file, lineno, TFAIL, "%s != %lu got %lu", path, val, sys_val);
+	tst_res_(file, lineno, TFAIL, "%s != %lu got %lu (raw: %llu)",
+		path, val, expected_val, sys_val_64);
 }
 
 void tst_assert_file_int(const char *file, const int lineno, const char *path, const char *prefix, int val)
diff --git a/testcases/kernel/syscalls/shmctl/shmctl03.c b/testcases/kernel/syscalls/shmctl/shmctl03.c
index 9e1c2f099..dfe5f17e3 100644
--- a/testcases/kernel/syscalls/shmctl/shmctl03.c
+++ b/testcases/kernel/syscalls/shmctl/shmctl03.c
@@ -30,9 +30,20 @@ static void verify_ipcinfo(void)
 	else
 		tst_res(TPASS, "shmmin = 1");
 
-	TST_ASSERT_ULONG(PATH_KERN_SHMMAX, info.shmmax);
-	TST_ASSERT_ULONG(PATH_KERN_SHMMNI, info.shmmni);
-	TST_ASSERT_ULONG(PATH_KERN_SHMALL, info.shmall);
+	if (tst_is_compat_mode()) {
+		/*
+		 * On 64-bit kernel, shmmax is clamped to INT_MAX for 32-bit
+		 * compat syscall, while shmmni and shmall are truncated
+		 * to 32-bit.
+		 */
+		TST_ASSERT_ULONG(PATH_KERN_SHMMAX, info.shmmax, TST_ASSERT_SATURATED_INT);
+		TST_ASSERT_ULONG(PATH_KERN_SHMMNI, info.shmmni, TST_ASSERT_BITWISE);
+		TST_ASSERT_ULONG(PATH_KERN_SHMALL, info.shmall, TST_ASSERT_BITWISE);
+	} else {
+		TST_ASSERT_ULONG(PATH_KERN_SHMMAX, info.shmmax);
+		TST_ASSERT_ULONG(PATH_KERN_SHMMNI, info.shmmni);
+		TST_ASSERT_ULONG(PATH_KERN_SHMALL, info.shmall);
+	}
 }
 
 static struct tst_test test = {
-- 
2.55.0


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