avoid overflows in kernel/time.c
When the conversion factor between jiffies and milli- or microseconds is not a single multiply or divide, as for the case of HZ == 300, we currently do a multiply followed by a divide. The intervening result, however, is subject to overflows, especially since the fraction is not simplified (for HZ == 300, we multiply by 300 and divide by 1000). This is exposed to the user when passing a large timeout to poll(), for example. This patch replaces the multiply-divide with a reciprocal multiplication on 32-bit platforms. When the input is an unsigned long, there is no portable way to do this on 64-bit platforms there is no portable way to do this since it requires a 128-bit intermediate result (which gcc does support on 64-bit platforms but may generate libgcc calls, e.g. on 64-bit s390), but since the output is a 32-bit integer in the cases affected, just simplify the multiply-divide (*3/10 instead of *300/1000). The reciprocal multiply used can have off-by-one errors in the upper half of the valid output range. This could be avoided at the expense of having to deal with a potential 65-bit intermediate result. Since the intent is to avoid overflow problems and most of the other time conversions are only semiexact, the off-by-one errors were considered an acceptable tradeoff. At Ralf Baechle's suggestion, this version uses a Perl script to compute the necessary constants. We already have dependencies on Perl for kernel compiles. This does, however, require the Perl module Math::BigInt, which is included in the standard Perl distribution starting with version 5.8.0. In order to support older versions of Perl, include a table of canned constants in the script itself, and structure the script so that Math::BigInt isn't required if pulling values from said table. Running the script requires that the HZ value is available from the Makefile. Thus, this patch also adds the Kconfig variable CONFIG_HZ to the architectures which didn't already have it (alpha, cris, frv, h8300, m32r, m68k, m68knommu, sparc, v850, and xtensa.) It does *not* touch the sh or sh64 architectures, since Paul Mundt has dealt with those separately in the sh tree. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Cc: Ralf Baechle <ralf@linux-mips.org>, Cc: Sam Ravnborg <sam@ravnborg.org>, Cc: Paul Mundt <lethal@linux-sh.org>, Cc: Richard Henderson <rth@twiddle.net>, Cc: Michael Starvik <starvik@axis.com>, Cc: David Howells <dhowells@redhat.com>, Cc: Yoshinori Sato <ysato@users.sourceforge.jp>, Cc: Hirokazu Takata <takata@linux-m32r.org>, Cc: Geert Uytterhoeven <geert@linux-m68k.org>, Cc: Roman Zippel <zippel@linux-m68k.org>, Cc: William L. Irwin <sparclinux@vger.kernel.org>, Cc: Chris Zankel <chris@zankel.net>, Cc: H. Peter Anvin <hpa@zytor.com>, Cc: Jan Engelhardt <jengelh@computergmbh.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
H. Peter Anvin
Linus Torvalds
Родитель
7ef3d2fd17
Коммит
bdc807871d
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@ -615,6 +615,11 @@ config VERBOSE_MCHECK_ON
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Take the default (1) unless you want more control or more info.
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config HZ
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int
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default 1200 if ALPHA_RAWHIDE
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default 1024
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source "drivers/pci/Kconfig"
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source "drivers/eisa/Kconfig"
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@ -55,6 +55,10 @@ config CRIS
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bool
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default y
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config HZ
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int
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default 100
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source "init/Kconfig"
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menu "General setup"
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@ -57,6 +57,10 @@ config ARCH_HAS_ILOG2_U64
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bool
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default y
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config HZ
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int
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default 1000
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mainmenu "Fujitsu FR-V Kernel Configuration"
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source "init/Kconfig"
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@ -82,6 +82,10 @@ config PCI
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bool
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default n
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config HZ
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int
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default 100
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source "init/Kconfig"
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source "arch/h8300/Kconfig.cpu"
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@ -38,6 +38,10 @@ config NO_DMA
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config ARCH_SUPPORTS_AOUT
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def_bool y
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config HZ
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int
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default 100
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source "init/Kconfig"
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@ -55,6 +55,10 @@ config NO_DMA
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config ARCH_SUPPORTS_AOUT
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def_bool y
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config HZ
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int
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default 100
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mainmenu "Linux/68k Kernel Configuration"
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source "init/Kconfig"
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@ -525,6 +525,11 @@ config 4KSTACKS
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running more threads on a system and also reduces the pressure
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on the VM subsystem for higher order allocations.
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config HZ
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int
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default 1000 if CLEOPATRA
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default 100
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comment "RAM configuration"
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config RAMBASE
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@ -30,6 +30,10 @@ config OF
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config ARCH_SUPPORTS_AOUT
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def_bool y
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config HZ
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int
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default 100
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source "init/Kconfig"
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menu "General machine setup"
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@ -215,6 +215,13 @@ menu "Processor type and features"
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bool
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default !V850E_CACHE && !V850E2_CACHE
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# HZ depends on the platform
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config HZ
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int
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default 24 if V850E_SIM || V850E2_SIM85E2
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default 122 if V850E2_FPGA85E2C
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default 100
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#### Misc config
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config ROM_KERNEL
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@ -49,6 +49,10 @@ config ARCH_HAS_ILOG2_U64
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config NO_IOPORT
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def_bool y
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config HZ
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int
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default 100
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source "init/Kconfig"
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menu "Processor type and features"
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@ -5,15 +5,7 @@
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hardware ignores reprogramming. We also need userland buy-in to the
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change in HZ, since this is visible in the wait4 resources etc. */
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#ifndef HZ
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# ifndef CONFIG_ALPHA_RAWHIDE
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# define HZ 1024
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# else
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# define HZ 1200
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# endif
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#endif
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#define HZ CONFIG_HZ
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#define USER_HZ HZ
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#define EXEC_PAGESIZE 8192
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@ -3,7 +3,7 @@
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/* Currently we assume that HZ=100 is good for CRIS. */
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#ifdef __KERNEL__
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# define HZ 100 /* Internal kernel timer frequency */
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# define HZ CONFIG_HZ /* Internal kernel timer frequency */
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# define USER_HZ 100 /* .. some user interfaces are in "ticks" */
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# define CLOCKS_PER_SEC (USER_HZ) /* like times() */
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#endif
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@ -2,7 +2,7 @@
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#define _ASM_PARAM_H
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#ifdef __KERNEL__
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#define HZ 1000 /* Internal kernel timer frequency */
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#define HZ CONFIG_HZ /* Internal kernel timer frequency */
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#define USER_HZ 100 /* .. some user interfaces are in "ticks" */
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#define CLOCKS_PER_SEC (USER_HZ) /* like times() */
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#endif
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@ -3,7 +3,7 @@
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#ifndef HZ
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#define HZ 100
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#define HZ CONFIG_HZ
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#endif
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#ifdef __KERNEL__
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@ -2,7 +2,7 @@
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#define _ASM_M32R_PARAM_H
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#ifdef __KERNEL__
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# define HZ 100 /* Internal kernel timer frequency */
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# define HZ CONFIG_HZ /* Internal kernel timer frequency */
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# define USER_HZ 100 /* .. some user interfaces are in "ticks" */
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# define CLOCKS_PER_SEC (USER_HZ) /* like times() */
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#endif
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@ -2,7 +2,7 @@
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#define _M68K_PARAM_H
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#ifdef __KERNEL__
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# define HZ 100 /* Internal kernel timer frequency */
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# define HZ CONFIG_HZ /* Internal kernel timer frequency */
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# define USER_HZ 100 /* .. some user interfaces are in "ticks" */
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# define CLOCKS_PER_SEC (USER_HZ) /* like times() */
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#endif
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@ -1,13 +1,7 @@
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#ifndef _M68KNOMMU_PARAM_H
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#define _M68KNOMMU_PARAM_H
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#if defined(CONFIG_CLEOPATRA)
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#define HZ 1000
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#endif
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#ifndef HZ
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#define HZ 100
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#endif
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#define HZ CONFIG_HZ
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#ifdef __KERNEL__
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#define USER_HZ HZ
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@ -3,7 +3,7 @@
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#define _ASMSPARC_PARAM_H
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#ifdef __KERNEL__
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# define HZ 100 /* Internal kernel timer frequency */
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# define HZ CONFIG_HZ /* Internal kernel timer frequency */
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# define USER_HZ 100 /* .. some user interfaces are in "ticks" */
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# define CLOCKS_PER_SEC (USER_HZ)
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#endif
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@ -134,10 +134,4 @@ extern void anna_uart_pre_configure (unsigned chan,
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#define V850E_TIMER_D_TMCD_CS_MIN 1 /* min 2^1 divider */
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/* For <asm/param.h> */
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#ifndef HZ
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#define HZ 100
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#endif
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#endif /* __V850_ANNA_H__ */
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@ -149,10 +149,4 @@ extern void as85ep1_uart_pre_configure (unsigned chan,
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#define V850E_TIMER_D_TMCD_CS_MIN 2 /* min 2^2 divider */
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/* For <asm/param.h> */
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#ifndef HZ
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#define HZ 100
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#endif
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#endif /* __V850_AS85EP1_H__ */
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@ -79,10 +79,4 @@ extern char _r0_ram;
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#endif
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/* For <asm/param.h> */
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#ifndef HZ
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#define HZ 122 /* actually, 8.192ms ticks =~ 122.07 */
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#endif
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#endif /* __V850_FPGA85E2C_H__ */
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@ -23,8 +23,7 @@
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#define MAXHOSTNAMELEN 64 /* max length of hostname */
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#ifdef __KERNEL__
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#include <asm/machdep.h> /* For HZ */
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# define HZ CONFIG_HZ
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# define USER_HZ 100
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# define CLOCKS_PER_SEC USER_HZ
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#endif
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@ -69,12 +69,6 @@
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#endif /* CONFIG_RTE_MB_A_PCI */
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/* For <asm/param.h> */
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#ifndef HZ
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#define HZ 100
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#endif
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#ifndef __ASSEMBLY__
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extern void rte_cb_early_init (void);
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extern void rte_cb_init_irqs (void);
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@ -40,11 +40,6 @@
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#define R0_RAM_ADDR 0xFFFFF000
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/* For <asm/param.h> */
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#ifndef HZ
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#define HZ 24 /* Minimum supported frequency. */
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#endif
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/* For <asm/irq.h> */
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#define NUM_CPU_IRQS 6
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@ -66,10 +66,4 @@
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#define R0_RAM_ADDR 0xFFFFE000
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/* For <asm/param.h> */
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#ifndef HZ
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#define HZ 24 /* Minimum supported frequency. */
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#endif
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#endif /* __V850_SIM85E2_H__ */
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@ -12,7 +12,7 @@
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#define _XTENSA_PARAM_H
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#ifdef __KERNEL__
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# define HZ 100 /* internal timer frequency */
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# define HZ CONFIG_HZ /* internal timer frequency */
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# define USER_HZ 100 /* for user interfaces in "ticks" */
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# define CLOCKS_PER_SEC (USER_HZ) /* frequnzy at which times() counts */
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#endif
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@ -91,3 +91,11 @@ quiet_cmd_ikconfiggz = IKCFG $@
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targets += config_data.h
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$(obj)/config_data.h: $(obj)/config_data.gz FORCE
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$(call if_changed,ikconfiggz)
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$(obj)/time.o: $(obj)/timeconst.h
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quiet_cmd_timeconst = TIMEC $@
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cmd_timeconst = $(PERL) $< $(CONFIG_HZ) > $@
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targets += timeconst.h
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$(obj)/timeconst.h: $(src)/timeconst.pl FORCE
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$(call if_changed,timeconst)
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|
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@ -39,6 +39,8 @@
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#include <asm/uaccess.h>
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#include <asm/unistd.h>
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#include "timeconst.h"
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/*
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* The timezone where the local system is located. Used as a default by some
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* programs who obtain this value by using gettimeofday.
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@ -93,7 +95,8 @@ asmlinkage long sys_stime(time_t __user *tptr)
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#endif /* __ARCH_WANT_SYS_TIME */
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asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
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asmlinkage long sys_gettimeofday(struct timeval __user *tv,
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struct timezone __user *tz)
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{
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if (likely(tv != NULL)) {
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struct timeval ktv;
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@ -118,7 +121,7 @@ asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __us
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* hard to make the program warp the clock precisely n hours) or
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* compile in the timezone information into the kernel. Bad, bad....
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*
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* - TYT, 1992-01-01
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* - TYT, 1992-01-01
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*
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* The best thing to do is to keep the CMOS clock in universal time (UTC)
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* as real UNIX machines always do it. This avoids all headaches about
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@ -240,7 +243,11 @@ unsigned int inline jiffies_to_msecs(const unsigned long j)
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#elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
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return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
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#else
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return (j * MSEC_PER_SEC) / HZ;
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# if BITS_PER_LONG == 32
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return ((u64)HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
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# else
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return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
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# endif
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#endif
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}
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EXPORT_SYMBOL(jiffies_to_msecs);
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@ -252,7 +259,11 @@ unsigned int inline jiffies_to_usecs(const unsigned long j)
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#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
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return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
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#else
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return (j * USEC_PER_SEC) / HZ;
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# if BITS_PER_LONG == 32
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return ((u64)HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
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# else
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return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
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# endif
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#endif
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}
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EXPORT_SYMBOL(jiffies_to_usecs);
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@ -352,7 +363,7 @@ EXPORT_SYMBOL(mktime);
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* normalize to the timespec storage format
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*
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* Note: The tv_nsec part is always in the range of
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* 0 <= tv_nsec < NSEC_PER_SEC
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* 0 <= tv_nsec < NSEC_PER_SEC
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* For negative values only the tv_sec field is negative !
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*/
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void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
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@ -453,12 +464,13 @@ unsigned long msecs_to_jiffies(const unsigned int m)
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/*
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* Generic case - multiply, round and divide. But first
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* check that if we are doing a net multiplication, that
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* we wouldnt overflow:
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* we wouldn't overflow:
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*/
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if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
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return MAX_JIFFY_OFFSET;
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return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
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return ((u64)MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
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>> MSEC_TO_HZ_SHR32;
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#endif
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||||
}
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||||
EXPORT_SYMBOL(msecs_to_jiffies);
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||||
|
|
@ -472,7 +484,8 @@ unsigned long usecs_to_jiffies(const unsigned int u)
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#elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
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return u * (HZ / USEC_PER_SEC);
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||||
#else
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||||
return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC;
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return ((u64)USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32)
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>> USEC_TO_HZ_SHR32;
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||||
#endif
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||||
}
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||||
EXPORT_SYMBOL(usecs_to_jiffies);
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||||
|
|
|
|||
|
|
@ -0,0 +1,402 @@
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|||
#!/usr/bin/perl
|
||||
# -----------------------------------------------------------------------
|
||||
#
|
||||
# Copyright 2007 rPath, Inc. - All Rights Reserved
|
||||
#
|
||||
# This file is part of the Linux kernel, and is made available under
|
||||
# the terms of the GNU General Public License version 2 or (at your
|
||||
# option) any later version; incorporated herein by reference.
|
||||
#
|
||||
# -----------------------------------------------------------------------
|
||||
#
|
||||
|
||||
#
|
||||
# Usage: timeconst.pl HZ > timeconst.h
|
||||
#
|
||||
|
||||
# Precomputed values for systems without Math::BigInt
|
||||
# Generated by:
|
||||
# timeconst.pl --can 24 32 48 64 100 122 128 200 250 256 300 512 1000 1024 1200
|
||||
%canned_values = (
|
||||
24 => [
|
||||
'0xa6aaaaab','0x2aaaaaa',26,
|
||||
'0xa6aaaaaaaaaaaaab','0x2aaaaaaaaaaaaaa',58,
|
||||
125,3,
|
||||
'0xc49ba5e4','0x1fbe76c8b4',37,
|
||||
'0xc49ba5e353f7ceda','0x1fbe76c8b439581062',69,
|
||||
3,125,
|
||||
'0xa2c2aaab','0xaaaa',16,
|
||||
'0xa2c2aaaaaaaaaaab','0xaaaaaaaaaaaa',48,
|
||||
125000,3,
|
||||
'0xc9539b89','0x7fffbce4217d',47,
|
||||
'0xc9539b8887229e91','0x7fffbce4217d2849cb25',79,
|
||||
3,125000,
|
||||
], 32 => [
|
||||
'0xfa000000','0x6000000',27,
|
||||
'0xfa00000000000000','0x600000000000000',59,
|
||||
125,4,
|
||||
'0x83126e98','0xfdf3b645a',36,
|
||||
'0x83126e978d4fdf3c','0xfdf3b645a1cac0831',68,
|
||||
4,125,
|
||||
'0xf4240000','0x0',17,
|
||||
'0xf424000000000000','0x0',49,
|
||||
31250,1,
|
||||
'0x8637bd06','0x3fff79c842fa',46,
|
||||
'0x8637bd05af6c69b6','0x3fff79c842fa5093964a',78,
|
||||
1,31250,
|
||||
], 48 => [
|
||||
'0xa6aaaaab','0x6aaaaaa',27,
|
||||
'0xa6aaaaaaaaaaaaab','0x6aaaaaaaaaaaaaa',59,
|
||||
125,6,
|
||||
'0xc49ba5e4','0xfdf3b645a',36,
|
||||
'0xc49ba5e353f7ceda','0xfdf3b645a1cac0831',68,
|
||||
6,125,
|
||||
'0xa2c2aaab','0x15555',17,
|
||||
'0xa2c2aaaaaaaaaaab','0x1555555555555',49,
|
||||
62500,3,
|
||||
'0xc9539b89','0x3fffbce4217d',46,
|
||||
'0xc9539b8887229e91','0x3fffbce4217d2849cb25',78,
|
||||
3,62500,
|
||||
], 64 => [
|
||||
'0xfa000000','0xe000000',28,
|
||||
'0xfa00000000000000','0xe00000000000000',60,
|
||||
125,8,
|
||||
'0x83126e98','0x7ef9db22d',35,
|
||||
'0x83126e978d4fdf3c','0x7ef9db22d0e560418',67,
|
||||
8,125,
|
||||
'0xf4240000','0x0',18,
|
||||
'0xf424000000000000','0x0',50,
|
||||
15625,1,
|
||||
'0x8637bd06','0x1fff79c842fa',45,
|
||||
'0x8637bd05af6c69b6','0x1fff79c842fa5093964a',77,
|
||||
1,15625,
|
||||
], 100 => [
|
||||
'0xa0000000','0x0',28,
|
||||
'0xa000000000000000','0x0',60,
|
||||
10,1,
|
||||
'0xcccccccd','0x733333333',35,
|
||||
'0xcccccccccccccccd','0x73333333333333333',67,
|
||||
1,10,
|
||||
'0x9c400000','0x0',18,
|
||||
'0x9c40000000000000','0x0',50,
|
||||
10000,1,
|
||||
'0xd1b71759','0x1fff2e48e8a7',45,
|
||||
'0xd1b71758e219652c','0x1fff2e48e8a71de69ad4',77,
|
||||
1,10000,
|
||||
], 122 => [
|
||||
'0x8325c53f','0xfbcda3a',28,
|
||||
'0x8325c53ef368eb05','0xfbcda3ac10c9714',60,
|
||||
500,61,
|
||||
'0xf9db22d1','0x7fbe76c8b',35,
|
||||
'0xf9db22d0e560418a','0x7fbe76c8b43958106',67,
|
||||
61,500,
|
||||
'0x8012e2a0','0x3ef36',18,
|
||||
'0x8012e29f79b47583','0x3ef368eb04325',50,
|
||||
500000,61,
|
||||
'0xffda4053','0x1ffffbce4217',45,
|
||||
'0xffda4052d666a983','0x1ffffbce4217d2849cb2',77,
|
||||
61,500000,
|
||||
], 128 => [
|
||||
'0xfa000000','0x1e000000',29,
|
||||
'0xfa00000000000000','0x1e00000000000000',61,
|
||||
125,16,
|
||||
'0x83126e98','0x3f7ced916',34,
|
||||
'0x83126e978d4fdf3c','0x3f7ced916872b020c',66,
|
||||
16,125,
|
||||
'0xf4240000','0x40000',19,
|
||||
'0xf424000000000000','0x4000000000000',51,
|
||||
15625,2,
|
||||
'0x8637bd06','0xfffbce4217d',44,
|
||||
'0x8637bd05af6c69b6','0xfffbce4217d2849cb25',76,
|
||||
2,15625,
|
||||
], 200 => [
|
||||
'0xa0000000','0x0',29,
|
||||
'0xa000000000000000','0x0',61,
|
||||
5,1,
|
||||
'0xcccccccd','0x333333333',34,
|
||||
'0xcccccccccccccccd','0x33333333333333333',66,
|
||||
1,5,
|
||||
'0x9c400000','0x0',19,
|
||||
'0x9c40000000000000','0x0',51,
|
||||
5000,1,
|
||||
'0xd1b71759','0xfff2e48e8a7',44,
|
||||
'0xd1b71758e219652c','0xfff2e48e8a71de69ad4',76,
|
||||
1,5000,
|
||||
], 250 => [
|
||||
'0x80000000','0x0',29,
|
||||
'0x8000000000000000','0x0',61,
|
||||
4,1,
|
||||
'0x80000000','0x180000000',33,
|
||||
'0x8000000000000000','0x18000000000000000',65,
|
||||
1,4,
|
||||
'0xfa000000','0x0',20,
|
||||
'0xfa00000000000000','0x0',52,
|
||||
4000,1,
|
||||
'0x83126e98','0x7ff7ced9168',43,
|
||||
'0x83126e978d4fdf3c','0x7ff7ced916872b020c4',75,
|
||||
1,4000,
|
||||
], 256 => [
|
||||
'0xfa000000','0x3e000000',30,
|
||||
'0xfa00000000000000','0x3e00000000000000',62,
|
||||
125,32,
|
||||
'0x83126e98','0x1fbe76c8b',33,
|
||||
'0x83126e978d4fdf3c','0x1fbe76c8b43958106',65,
|
||||
32,125,
|
||||
'0xf4240000','0xc0000',20,
|
||||
'0xf424000000000000','0xc000000000000',52,
|
||||
15625,4,
|
||||
'0x8637bd06','0x7ffde7210be',43,
|
||||
'0x8637bd05af6c69b6','0x7ffde7210be9424e592',75,
|
||||
4,15625,
|
||||
], 300 => [
|
||||
'0xd5555556','0x2aaaaaaa',30,
|
||||
'0xd555555555555556','0x2aaaaaaaaaaaaaaa',62,
|
||||
10,3,
|
||||
'0x9999999a','0x1cccccccc',33,
|
||||
'0x999999999999999a','0x1cccccccccccccccc',65,
|
||||
3,10,
|
||||
'0xd0555556','0xaaaaa',20,
|
||||
'0xd055555555555556','0xaaaaaaaaaaaaa',52,
|
||||
10000,3,
|
||||
'0x9d495183','0x7ffcb923a29',43,
|
||||
'0x9d495182a9930be1','0x7ffcb923a29c779a6b5',75,
|
||||
3,10000,
|
||||
], 512 => [
|
||||
'0xfa000000','0x7e000000',31,
|
||||
'0xfa00000000000000','0x7e00000000000000',63,
|
||||
125,64,
|
||||
'0x83126e98','0xfdf3b645',32,
|
||||
'0x83126e978d4fdf3c','0xfdf3b645a1cac083',64,
|
||||
64,125,
|
||||
'0xf4240000','0x1c0000',21,
|
||||
'0xf424000000000000','0x1c000000000000',53,
|
||||
15625,8,
|
||||
'0x8637bd06','0x3ffef39085f',42,
|
||||
'0x8637bd05af6c69b6','0x3ffef39085f4a1272c9',74,
|
||||
8,15625,
|
||||
], 1000 => [
|
||||
'0x80000000','0x0',31,
|
||||
'0x8000000000000000','0x0',63,
|
||||
1,1,
|
||||
'0x80000000','0x0',31,
|
||||
'0x8000000000000000','0x0',63,
|
||||
1,1,
|
||||
'0xfa000000','0x0',22,
|
||||
'0xfa00000000000000','0x0',54,
|
||||
1000,1,
|
||||
'0x83126e98','0x1ff7ced9168',41,
|
||||
'0x83126e978d4fdf3c','0x1ff7ced916872b020c4',73,
|
||||
1,1000,
|
||||
], 1024 => [
|
||||
'0xfa000000','0xfe000000',32,
|
||||
'0xfa00000000000000','0xfe00000000000000',64,
|
||||
125,128,
|
||||
'0x83126e98','0x7ef9db22',31,
|
||||
'0x83126e978d4fdf3c','0x7ef9db22d0e56041',63,
|
||||
128,125,
|
||||
'0xf4240000','0x3c0000',22,
|
||||
'0xf424000000000000','0x3c000000000000',54,
|
||||
15625,16,
|
||||
'0x8637bd06','0x1fff79c842f',41,
|
||||
'0x8637bd05af6c69b6','0x1fff79c842fa5093964',73,
|
||||
16,15625,
|
||||
], 1200 => [
|
||||
'0xd5555556','0xd5555555',32,
|
||||
'0xd555555555555556','0xd555555555555555',64,
|
||||
5,6,
|
||||
'0x9999999a','0x66666666',31,
|
||||
'0x999999999999999a','0x6666666666666666',63,
|
||||
6,5,
|
||||
'0xd0555556','0x2aaaaa',22,
|
||||
'0xd055555555555556','0x2aaaaaaaaaaaaa',54,
|
||||
2500,3,
|
||||
'0x9d495183','0x1ffcb923a29',41,
|
||||
'0x9d495182a9930be1','0x1ffcb923a29c779a6b5',73,
|
||||
3,2500,
|
||||
]
|
||||
);
|
||||
|
||||
$has_bigint = eval 'use Math::BigInt qw(bgcd); 1;';
|
||||
|
||||
sub bint($)
|
||||
{
|
||||
my($x) = @_;
|
||||
return Math::BigInt->new($x);
|
||||
}
|
||||
|
||||
#
|
||||
# Constants for division by reciprocal multiplication.
|
||||
# (bits, numerator, denominator)
|
||||
#
|
||||
sub fmul($$$)
|
||||
{
|
||||
my ($b,$n,$d) = @_;
|
||||
|
||||
$n = bint($n);
|
||||
$d = bint($d);
|
||||
|
||||
return scalar (($n << $b)+$d-bint(1))/$d;
|
||||
}
|
||||
|
||||
sub fadj($$$)
|
||||
{
|
||||
my($b,$n,$d) = @_;
|
||||
|
||||
$n = bint($n);
|
||||
$d = bint($d);
|
||||
|
||||
$d = $d/bgcd($n, $d);
|
||||
return scalar (($d-bint(1)) << $b)/$d;
|
||||
}
|
||||
|
||||
sub fmuls($$$) {
|
||||
my($b,$n,$d) = @_;
|
||||
my($s,$m);
|
||||
my($thres) = bint(1) << ($b-1);
|
||||
|
||||
$n = bint($n);
|
||||
$d = bint($d);
|
||||
|
||||
for ($s = 0; 1; $s++) {
|
||||
$m = fmul($s,$n,$d);
|
||||
return $s if ($m >= $thres);
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
# Provides mul, adj, and shr factors for a specific
|
||||
# (bit, time, hz) combination
|
||||
sub muladj($$$) {
|
||||
my($b, $t, $hz) = @_;
|
||||
my $s = fmuls($b, $t, $hz);
|
||||
my $m = fmul($s, $t, $hz);
|
||||
my $a = fadj($s, $t, $hz);
|
||||
return ($m->as_hex(), $a->as_hex(), $s);
|
||||
}
|
||||
|
||||
# Provides numerator, denominator values
|
||||
sub numden($$) {
|
||||
my($n, $d) = @_;
|
||||
my $g = bgcd($n, $d);
|
||||
return ($n/$g, $d/$g);
|
||||
}
|
||||
|
||||
# All values for a specific (time, hz) combo
|
||||
sub conversions($$) {
|
||||
my ($t, $hz) = @_;
|
||||
my @val = ();
|
||||
|
||||
# HZ_TO_xx
|
||||
push(@val, muladj(32, $t, $hz));
|
||||
push(@val, muladj(64, $t, $hz));
|
||||
push(@val, numden($t, $hz));
|
||||
|
||||
# xx_TO_HZ
|
||||
push(@val, muladj(32, $hz, $t));
|
||||
push(@val, muladj(64, $hz, $t));
|
||||
push(@val, numden($hz, $t));
|
||||
|
||||
return @val;
|
||||
}
|
||||
|
||||
sub compute_values($) {
|
||||
my($hz) = @_;
|
||||
my @val = ();
|
||||
my $s, $m, $a, $g;
|
||||
|
||||
if (!$has_bigint) {
|
||||
die "$0: HZ == $hz not canned and ".
|
||||
"Math::BigInt not available\n";
|
||||
}
|
||||
|
||||
# MSEC conversions
|
||||
push(@val, conversions(1000, $hz));
|
||||
|
||||
# USEC conversions
|
||||
push(@val, conversions(1000000, $hz));
|
||||
|
||||
return @val;
|
||||
}
|
||||
|
||||
sub output($@)
|
||||
{
|
||||
my($hz, @val) = @_;
|
||||
my $pfx, $bit, $suf, $s, $m, $a;
|
||||
|
||||
print "/* Automatically generated by kernel/timeconst.pl */\n";
|
||||
print "/* Conversion constants for HZ == $hz */\n";
|
||||
print "\n";
|
||||
print "#ifndef KERNEL_TIMECONST_H\n";
|
||||
print "#define KERNEL_TIMECONST_H\n";
|
||||
print "\n";
|
||||
|
||||
print "#include <linux/param.h>\n";
|
||||
|
||||
print "\n";
|
||||
print "#if HZ != $hz\n";
|
||||
print "#error \"kernel/timeconst.h has the wrong HZ value!\"\n";
|
||||
print "#endif\n";
|
||||
print "\n";
|
||||
|
||||
foreach $pfx ('HZ_TO_MSEC','MSEC_TO_HZ',
|
||||
'USEC_TO_HZ','HZ_TO_USEC') {
|
||||
foreach $bit (32, 64) {
|
||||
foreach $suf ('MUL', 'ADJ', 'SHR') {
|
||||
printf "#define %-23s %s\n",
|
||||
"${pfx}_$suf$bit", shift(@val);
|
||||
}
|
||||
}
|
||||
foreach $suf ('NUM', 'DEN') {
|
||||
printf "#define %-23s %s\n",
|
||||
"${pfx}_$suf", shift(@val);
|
||||
}
|
||||
}
|
||||
|
||||
print "\n";
|
||||
print "#endif /* KERNEL_TIMECONST_H */\n";
|
||||
}
|
||||
|
||||
($hz) = @ARGV;
|
||||
|
||||
# Use this to generate the %canned_values structure
|
||||
if ($hz eq '--can') {
|
||||
shift(@ARGV);
|
||||
@hzlist = sort {$a <=> $b} (@ARGV);
|
||||
|
||||
print "# Precomputed values for systems without Math::BigInt\n";
|
||||
print "# Generated by:\n";
|
||||
print "# timeconst.pl --can ", join(' ', @hzlist), "\n";
|
||||
print "\%canned_values = (\n";
|
||||
my $pf = "\t";
|
||||
foreach $hz (@hzlist) {
|
||||
my @values = compute_values($hz);
|
||||
print "$pf$hz => [\n";
|
||||
while (scalar(@values)) {
|
||||
my $bit;
|
||||
foreach $bit (32, 64) {
|
||||
my $m = shift(@values);
|
||||
my $a = shift(@values);
|
||||
my $s = shift(@values);
|
||||
print "\t\t\'",$m,"\',\'",$a,"\',",$s,",\n";
|
||||
}
|
||||
my $n = shift(@values);
|
||||
my $d = shift(@values);
|
||||
print "\t\t",$n,',',$d,",\n";
|
||||
}
|
||||
print "\t]";
|
||||
$pf = ', ';
|
||||
}
|
||||
print "\n);\n";
|
||||
} else {
|
||||
$hz += 0; # Force to number
|
||||
if ($hz < 1) {
|
||||
die "Usage: $0 HZ\n";
|
||||
}
|
||||
|
||||
@val = @{$canned_values{$hz}};
|
||||
if (!defined(@val)) {
|
||||
@val = compute_values($hz);
|
||||
}
|
||||
output($hz, @val);
|
||||
}
|
||||
exit 0;
|
||||
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Ссылка в новой задаче