[PATCH next 1/3] fortify: replace __compiletime_lessthan() with statically_true()

david.laight.linux
2026-03-30T13:20:11Z

From: David Laight <david.laight.linux@gmail.com>

__compiletime_lessthan(a, b) is exactly the same as statically_true(a < b)
Replace the former by the latter.

Signed-off-by: David Laight <david.laight.linux@gmail.com>
---
include/linux/fortify-string.h | 47 +++++++++++++++-------------------
1 file changed, 21 insertions(+), 26 deletions(-)

diff --git a/include/linux/fortify-string.h b/include/linux/fortify-string.h
index 171982e53c9a..214d237214d5 100644
--- a/include/linux/fortify-string.h
+++ b/include/linux/fortify-string.h
@@ -154,11 +154,6 @@ extern char *__underlying_strncpy(char *p, const char *q, __kernel_size_t size)
#define POS0 __pass_object_size(0)
#endif

-#define __compiletime_lessthan(bounds, length) ( \
- __builtin_constant_p((bounds) < (length)) && \
- (bounds) < (length) \
-)
-
/**
* strncpy - Copy a string to memory with non-guaranteed NUL padding
*
@@ -196,7 +191,7 @@ char *strncpy(char * const POS p, const char *q, __kernel_size_t size)
{
const size_t p_size = __member_size(p);

- if (__compiletime_lessthan(p_size, size))
+ if (statically_true(p_size < size))
__write_overflow();
if (p_size < size)
fortify_panic(FORTIFY_FUNC_strncpy, FORTIFY_WRITE, p_size, size, p);
@@ -287,14 +282,14 @@ __FORTIFY_INLINE ssize_t sized_strscpy(char * const POS p, const char * const PO
* If size can be known at compile time and is greater than
* p_size, generate a compile time write overflow error.
*/
- if (__compiletime_lessthan(p_size, size))
+ if (statically_true(p_size < size))
__write_overflow();

/* Short-circuit for compile-time known-safe lengths. */
- if (__compiletime_lessthan(p_size, SIZE_MAX)) {
+ if (statically_true(p_size < SIZE_MAX)) {
len = __compiletime_strlen(q);

- if (len < SIZE_MAX && __compiletime_lessthan(len, size)) {
+ if (len < SIZE_MAX && statically_true(len < size)) {
__underlying_memcpy(p, q, len + 1);
return len;
}
@@ -469,12 +464,12 @@ __FORTIFY_INLINE bool fortify_memset_chk(__kernel_size_t size,
*/

/* Error when size is larger than enclosing struct. */
- if (__compiletime_lessthan(p_size_field, p_size) &&
- __compiletime_lessthan(p_size, size))
+ if (statically_true(p_size_field < p_size) &&
+ statically_true(p_size < size))
__write_overflow();

/* Warn when write size is larger than dest field. */
- if (__compiletime_lessthan(p_size_field, size))
+ if (statically_true(p_size_field < size))
__write_overflow_field(p_size_field, size);
}
/*
@@ -557,15 +552,15 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
*/

/* Error when size is larger than enclosing struct. */
- if (__compiletime_lessthan(p_size_field, p_size) &&
- __compiletime_lessthan(p_size, size))
+ if (statically_true(p_size_field < p_size) &&
+ statically_true(p_size < size))
__write_overflow();
- if (__compiletime_lessthan(q_size_field, q_size) &&
- __compiletime_lessthan(q_size, size))
+ if (statically_true(q_size_field < q_size) &&
+ statically_true(q_size < size))
__read_overflow2();

/* Warn when write size argument larger than dest field. */
- if (__compiletime_lessthan(p_size_field, size))
+ if (statically_true(p_size_field < size))
__write_overflow_field(p_size_field, size);
/*
* Warn for source field over-read when building with W=1
@@ -573,8 +568,8 @@ __FORTIFY_INLINE bool fortify_memcpy_chk(__kernel_size_t size,
* the same time.
*/
if ((IS_ENABLED(KBUILD_EXTRA_WARN1) ||
- __compiletime_lessthan(p_size_field, size)) &&
- __compiletime_lessthan(q_size_field, size))
+ statically_true(p_size_field < size)) &&
+ statically_true(q_size_field < size))
__read_overflow2_field(q_size_field, size);
}
/*
@@ -699,7 +694,7 @@ __FORTIFY_INLINE void *memscan(void * const POS0 p, int c, __kernel_size_t size)
{
const size_t p_size = __struct_size(p);

- if (__compiletime_lessthan(p_size, size))
+ if (statically_true(p_size < size))
__read_overflow();
if (p_size < size)
fortify_panic(FORTIFY_FUNC_memscan, FORTIFY_READ, p_size, size, NULL);
@@ -713,9 +708,9 @@ int memcmp(const void * const POS0 p, const void * const POS0 q, __kernel_size_t
const size_t q_size = __struct_size(q);

if (__builtin_constant_p(size)) {
- if (__compiletime_lessthan(p_size, size))
+ if (statically_true(p_size < size))
__read_overflow();
- if (__compiletime_lessthan(q_size, size))
+ if (statically_true(q_size < size))
__read_overflow2();
}
if (p_size < size)
@@ -730,7 +725,7 @@ void *memchr(const void * const POS0 p, int c, __kernel_size_t size)
{
const size_t p_size = __struct_size(p);

- if (__compiletime_lessthan(p_size, size))
+ if (statically_true(p_size < size))
__read_overflow();
if (p_size < size)
fortify_panic(FORTIFY_FUNC_memchr, FORTIFY_READ, p_size, size, NULL);
@@ -742,7 +737,7 @@ __FORTIFY_INLINE void *memchr_inv(const void * const POS0 p, int c, size_t size)
{
const size_t p_size = __struct_size(p);

- if (__compiletime_lessthan(p_size, size))
+ if (statically_true(p_size < size))
__read_overflow();
if (p_size < size)
fortify_panic(FORTIFY_FUNC_memchr_inv, FORTIFY_READ, p_size, size, NULL);
@@ -755,7 +750,7 @@ __FORTIFY_INLINE void *kmemdup_noprof(const void * const POS0 p, size_t size, gf
{
const size_t p_size = __struct_size(p);

- if (__compiletime_lessthan(p_size, size))
+ if (statically_true(p_size < size))
__read_overflow();
if (p_size < size)
fortify_panic(FORTIFY_FUNC_kmemdup, FORTIFY_READ, p_size, size,
@@ -793,7 +788,7 @@ char *strcpy(char * const POS p, const char * const POS q)
return __underlying_strcpy(p, q);
size = strlen(q) + 1;
/* Compile-time check for const size overflow. */
- if (__compiletime_lessthan(p_size, size))
+ if (statically_true(p_size < size))
__write_overflow();
/* Run-time check for dynamic size overflow. */
if (p_size < size)
--
2.39.5