Messages in this thread Patches in this message | | | Date | Tue, 15 Sep 2015 14:21:20 -0700 | From | Andrew Morton <> | Subject | Re: [RFC][PATCH 0/5] Fixes for abs() usage on 64bit values |
| |
On Mon, 14 Sep 2015 23:46:32 -0400 Tejun Heo <tj@kernel.org> wrote:
> Anyways, let's please get abs() working for all types, one way or the > other.
That would be by far the best solution, of course.
This seems to work OK:
--- a/include/linux/kernel.h~a +++ a/include/linux/kernel.h @@ -207,8 +207,11 @@ extern int _cond_resched(void); * for those. */ #define abs(x) ({ \ - long ret; \ - if (sizeof(x) == sizeof(long)) { \ + s64 ret; \ + if (sizeof(x) == sizeof(s64)) { \ + s64 __x = (x); \ + ret = (__x < 0) ? -__x : __x; \ + } else if (sizeof(x) == sizeof(long)) { \ long __x = (x); \ ret = (__x < 0) ? -__x : __x; \ } else { \ Test case:
--- /dev/null +++ a/lib/xx.c @@ -0,0 +1,33 @@ +#include <linux/kernel.h> + +#define newabs(x) ({ \ + s64 ret; \ + if (sizeof(x) == sizeof(s64)) { \ + s64 __x = (x); \ + ret = (__x < 0) ? -__x : __x; \ + } else if (sizeof(x) == sizeof(long)) { \ + long __x = (x); \ + ret = (__x < 0) ? -__x : __x; \ + } else { \ + int __x = (x); \ + ret = (__x < 0) ? -__x : __x; \ + } \ + ret; \ + }) + +#define oldabs(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; \ + }) + +int foo(int x) +{ + return oldabs(x); +} diff -puN lib/Makefile~b lib/Makefile --- a/lib/Makefile~b +++ a/lib/Makefile @@ -13,7 +13,7 @@ lib-y := ctype.o string.o vsprintf.o cmd sha1.o md5.o irq_regs.o argv_split.o \ proportions.o flex_proportions.o ratelimit.o show_mem.o \ is_single_threaded.o plist.o decompress.o kobject_uevent.o \ - earlycpio.o seq_buf.o nmi_backtrace.o + earlycpio.o seq_buf.o nmi_backtrace.o xx.o obj-$(CONFIG_ARCH_HAS_DEBUG_STRICT_USER_COPY_CHECKS) += usercopy.o lib-$(CONFIG_MMU) += ioremap.o
on i386, xx.o's text is 68 bytes with either newabs() or oldabs().
lib/percpu_counter.o's text does get larger with newabs(). That's because __percpu_counter_compare() is doing abs() on an s64, doh.
| |