The patch titled
include/linux/kernel.h: abs(): fix handling of 32-bit unsigneds on 64-bit
has been removed from the -mm tree. Its filename was
include-linux-kernelh-abs-fix-handling-of-32-bit-unsigneds-on-64-bit.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: include/linux/kernel.h: abs(): fix handling of 32-bit unsigneds on 64-bit
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Michal reports:
In the framebuffer subsystem the abs() macro is often used as a part of
the calculation of a Manhattan metric, which in turn is used as a measure
of similarity between video modes. The arguments of abs() are sometimes
unsigned numbers. This worked fine until commit a49c59c0 ("Make sure the
value in abs() does not get truncated if it is greater than 2^32:) , which
changed the definition of abs() to prevent truncation. As a result of
this change, in the following piece of code:
u32 a = 0, b = 1;
u32 c = abs(a - b);
'c' will end up with a value of 0xffffffff instead of the expected 0x1.
A problem caused by this change and visible by the end user is that
framebuffer drivers relying on functions from modedb.c will fail to find
high resolution video modes similar to that explicitly requested by the
user if an exact match cannot be found (see e.g.
Fix this by special-casing `long' types within abs().
This patch reduces x86_64 code size a bit - drivers/video/uvesafb.o shrunk
by 15 bytes, presumably because it is doing abs() on 4-byte quantities,
and expanding those to 8-byte longs adds code.
testcase:
#define oldabs(x) ({ \
long __x = (x); \
(__x < 0) ? -__x : __x; \
})
#define newabs(x) ({ \
long ret; \
if (sizeof(x) == sizeof(long)) { \
long __x = (x); \
ret = (__x < 0) ? -__x : __x; \
} else { \
int __x = (x); \
ret = (__x < 0) ? -__x : __x; \
} \
ret; \
})
typedef unsigned int u32;
main()
{
u32 a = 0;
u32 b = 1;
u32 oldc = oldabs(a - b);
u32 newc = newabs(a - b);
printf("%u %u\n", oldc, newc);
}
akpm:/home/akpm> gcc t.c
akpm:/home/akpm> ./a.out
4294967295 1
Reported-by: Michal Januszewski <michalj@xxxxxxxxx>
Cc: Rolf Eike Beer <eike-kernel@xxxxxxxxx
Cc: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/kernel.h | 19 ++++++++++++++++---
1 file changed, 16 insertions(+), 3 deletions(-)
diff -puN include/linux/kernel.h~include-linux-kernelh-abs-fix-handling-of-32-bit-unsigneds-on-64-bit include/linux/kernel.h
--- a/include/linux/kernel.h~include-linux-kernelh-abs-fix-handling-of-32-bit-unsigneds-on-64-bit
+++ a/include/linux/kernel.h
@@ -143,9 +143,22 @@ extern int _cond_resched(void);
#define might_sleep_if(cond) do { if (cond) might_sleep(); } while (0)
-#define abs(x) ({ \
- long __x = (x); \
- (__x < 0) ? -__x : __x; \
+/*
+ * abs() handles unsigned and signed longs, ints, shorts and chars. For all
+ * input types abs() returns a signed long.
+ * abs() should not be used for 64-bit types (s64, u64, long long) - use abs64()
+ * for those.
+ */
+#define abs(x) ({ \
+ long ret; \
+ if (sizeof(x) == sizeof(long)) { \
+ long __x = (x); \
+ ret = (__x < 0) ? -__x : __x; \
+ } else { \
+ int __x = (x); \
+ ret = (__x < 0) ? -__x : __x; \
+ } \
+ ret; \
})
#define abs64(x) ({ \
_
Patches currently in -mm which might be from akpm@xxxxxxxxxxxxxxxxxxxx are
origin.patch
linux-next.patch
linux-next-git-rejects.patch
next-remove-localversion.patch
i-need-old-gcc.patch
arch-alpha-kernel-systblss-remove-debug-check.patch
arch-alpha-include-asm-ioh-s-extern-inline-static-inline.patch
mm-vmap-area-cache.patch
drivers-gpu-drm-radeon-atomc-fix-warning.patch
leds-route-kbd-leds-through-the-generic-leds-layer.patch
atmel_serial-fix-rts-high-after-initialization-in-rs485-mode-fix.patch
drivers-message-fusion-mptsasc-fix-warning.patch
mm.patch
mm-vmstat-use-a-single-setter-function-and-callback-for-adjusting-percpu-thresholds-fix.patch
writeback-check-skipped-pages-on-wb_sync_all-update-fix.patch
writeback-make-nr_to_write-a-per-file-limit-fix.patch
sync_inode_metadata-fix-comment.patch
fs-mpagec-consolidate-code-checkpatch-fixes.patch
mm-vmscan-reclaim-order-0-and-use-compaction-instead-of-lumpy-reclaim-fix.patch
mm-vmscan-reclaim-order-0-and-use-compaction-instead-of-lumpy-reclaim-avoid-a-potential-deadlock-due-to-lock_page-during-direct-compaction-fix.patch
mm-migration-allow-migration-to-operate-asynchronously-and-avoid-synchronous-compaction-in-the-faster-path-fix.patch
mm-deactivate-invalidated-pages-fix.patch
mlock-only-hold-mmap_sem-in-shared-mode-when-faulting-in-pages-fix.patch
mlock-do-not-hold-mmap_sem-for-extended-periods-of-time-fix.patch
writeback-avoid-unnecessary-determine_dirtyable_memory-call-fix.patch
thp-pte-alloc-trans-splitting-fix-checkpatch-fixes.patch
thp-kvm-mmu-transparent-hugepage-support-bisection.patch
thp-khugepaged-make-khugepaged-aware-of-madvise-fix.patch
mm-migration-use-rcu_dereference_protected-when-dereferencing-the-radix-tree-slot-during-file-page-migration-fix.patch
mm-hugetlbc-fix-error-path-memory-leak-in-nr_hugepages_store_common-fix.patch
brk-fix-min_brk-lower-bound-computation-for-compat_brk-fix.patch
mm-page_allocc-simplify-calculation-of-combined-index-of-adjacent-buddy-lists-checkpatch-fixes.patch
mm-page_allocc-simplify-calculation-of-combined-index-of-adjacent-buddy-lists-fix.patch
mm-dmapoolc-use-task_uninterruptible-in-dma_pool_alloc.patch
hugetlb-check-the-return-value-of-string-conversion-in-sysctl-handler-fix.patch
hugetlb-do-not-allow-pagesize-=-max_order-pool-adjustment-fix.patch
mm-fix-migration-hangs-on-anon_vma-lock-checkpatch-fixes.patch
mm-page_allocc-dont-cache-current-in-a-local.patch
mm-batch-activate_page-to-reduce-lock-contention-checkpatch-fixes.patch
frv-duplicate-output_buffer-of-e03-checkpatch-fixes.patch
hpet-factor-timer-allocate-from-open.patch
lib-hexdumpc-make-hex2bin-return-the-updated-src-address.patch
fs-binfmt_miscc-use-kernels-hex_to_bin-method-fix.patch
fs-binfmt_miscc-use-kernels-hex_to_bin-method-fix-fix.patch
memcg-document-cgroup-dirty-memory-interfaces-fix.patch
exec_domain-establish-a-linux32-domain-on-config_compat-systems.patch
scatterlist-new-helper-functions-fix.patch
journal_add_journal_head-debug.patch
slab-leaks3-default-y.patch
put_bh-debug.patch
memblock-add-input-size-checking-to-memblock_find_region.patch
memblock-add-input-size-checking-to-memblock_find_region-fix.patch
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