Re: [PATCH] ACPI: avoid NULL pointer arithmetic

From: Rafael J. Wysocki
Date: Tue Sep 28 2021 - 13:44:10 EST

Bob, this is ACPICA material.

Would it be possible to apply this to the upstream from the patch or do you need  a PR for this?

On 9/27/2021 2:13 PM, Arnd Bergmann wrote:
From: Arnd Bergmann <arnd@xxxxxxxx>

There are some very old macros for doing an open-coded offsetof() and
cast between pointer and integer in ACPI headers. clang-14 now complains
about these:

drivers/acpi/acpica/tbfadt.c:86:3: error: performing pointer subtraction with a null pointer has undefined behavior [-Werror,-Wnull-pointer-subtraction]
include/acpi/actbl.h:376:47: note: expanded from macro 'ACPI_FADT_OFFSET'
#define ACPI_FADT_OFFSET(f) (u16) ACPI_OFFSET (struct acpi_table_fadt, f)
include/acpi/actypes.h:511:41: note: expanded from macro 'ACPI_OFFSET'
#define ACPI_OFFSET(d, f) ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
include/acpi/actypes.h:505:79: note: expanded from macro 'ACPI_PTR_DIFF'
#define ACPI_PTR_DIFF(a, b) ((acpi_size) (ACPI_CAST_PTR (u8, (a)) - ACPI_CAST_PTR (u8, (b))))
^ ~~~~~~~~~~~~~~~~~~~~~~~
Convert them to the modern equivalents.

Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
include/acpi/actypes.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
index 92c71dfce0d5..285bc7b73de3 100644
--- a/include/acpi/actypes.h
+++ b/include/acpi/actypes.h
@@ -507,8 +507,8 @@ typedef u64 acpi_integer;
/* Pointer/Integer type conversions */
#define ACPI_TO_POINTER(i) ACPI_CAST_PTR (void, (acpi_size) (i))
-#define ACPI_TO_INTEGER(p) ACPI_PTR_DIFF (p, (void *) 0)
-#define ACPI_OFFSET(d, f) ACPI_PTR_DIFF (&(((d *) 0)->f), (void *) 0)
+#define ACPI_TO_INTEGER(p) ((uintptr_t)(p))
+#define ACPI_OFFSET(d, f) offsetof(d, f)