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    Subject[PATCH] Avoid overflows in kernel/time.c (version 3)
    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, sh64, sparc, v850, and xtensa.)

    Signed-off-by: H. Peter Anvin <hpa@zytor.com>
    ---
    arch/alpha/Kconfig | 5 +
    arch/cris/Kconfig | 4 +
    arch/frv/Kconfig | 4 +
    arch/h8300/Kconfig | 4 +
    arch/m32r/Kconfig | 4 +
    arch/m68k/Kconfig | 4 +
    arch/m68knommu/Kconfig | 5 +
    arch/sh64/Kconfig | 6 +
    arch/sparc/Kconfig | 4 +
    arch/v850/Kconfig | 7 +
    arch/xtensa/Kconfig | 4 +
    include/asm-alpha/param.h | 10 +-
    include/asm-cris/param.h | 2 +-
    include/asm-frv/param.h | 2 +-
    include/asm-h8300/param.h | 2 +-
    include/asm-m32r/param.h | 2 +-
    include/asm-m68k/param.h | 2 +-
    include/asm-m68knommu/param.h | 8 +-
    include/asm-sh64/param.h | 6 +-
    include/asm-sparc/param.h | 2 +-
    include/asm-v850/anna.h | 6 -
    include/asm-v850/as85ep1.h | 6 -
    include/asm-v850/fpga85e2c.h | 6 -
    include/asm-v850/param.h | 3 +-
    include/asm-v850/rte_cb.h | 6 -
    include/asm-v850/sim.h | 5 -
    include/asm-v850/sim85e2.h | 6 -
    include/asm-xtensa/param.h | 2 +-
    kernel/Makefile | 8 +
    kernel/time.c | 29 +++-
    kernel/timeconst.pl | 337 +++++++++++++++++++++++++++++++++++++++++
    31 files changed, 428 insertions(+), 73 deletions(-)
    create mode 100644 kernel/timeconst.pl

    diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
    index 4c002ba..442e4e7 100644
    --- a/arch/alpha/Kconfig
    +++ b/arch/alpha/Kconfig
    @@ -616,6 +616,11 @@ config VERBOSE_MCHECK_ON

    Take the default (1) unless you want more control or more info.

    +config HZ
    + int
    + default 1200 if ALPHA_RAWHIDE
    + default 1024
    +
    source "drivers/pci/Kconfig"
    source "drivers/eisa/Kconfig"

    diff --git a/arch/cris/Kconfig b/arch/cris/Kconfig
    index 222da15..fcc6a9e 100644
    --- a/arch/cris/Kconfig
    +++ b/arch/cris/Kconfig
    @@ -55,6 +55,10 @@ config CRIS
    bool
    default y

    +config HZ
    + int
    + default 100
    +
    source "init/Kconfig"

    menu "General setup"
    diff --git a/arch/frv/Kconfig b/arch/frv/Kconfig
    index 43153e7..57bdf2d 100644
    --- a/arch/frv/Kconfig
    +++ b/arch/frv/Kconfig
    @@ -57,6 +57,10 @@ config ARCH_HAS_ILOG2_U64
    bool
    default y

    +config HZ
    + int
    + default 1000
    +
    mainmenu "Fujitsu FR-V Kernel Configuration"

    source "init/Kconfig"
    diff --git a/arch/h8300/Kconfig b/arch/h8300/Kconfig
    index ff6a871..8a40a6f 100644
    --- a/arch/h8300/Kconfig
    +++ b/arch/h8300/Kconfig
    @@ -79,6 +79,10 @@ config PCI
    bool
    default n

    +config HZ
    + int
    + default 100
    +
    source "init/Kconfig"

    source "arch/h8300/Kconfig.cpu"
    diff --git a/arch/m32r/Kconfig b/arch/m32r/Kconfig
    index ab9a264..1547d81 100644
    --- a/arch/m32r/Kconfig
    +++ b/arch/m32r/Kconfig
    @@ -34,6 +34,10 @@ config NO_IOPORT
    config NO_DMA
    def_bool y

    +config HZ
    + int
    + default 100
    +
    source "init/Kconfig"


    diff --git a/arch/m68k/Kconfig b/arch/m68k/Kconfig
    index 01dee84..06ccc89 100644
    --- a/arch/m68k/Kconfig
    +++ b/arch/m68k/Kconfig
    @@ -52,6 +52,10 @@ config NO_IOPORT
    config NO_DMA
    def_bool SUN3

    +config HZ
    + int
    + default 100
    +
    mainmenu "Linux/68k Kernel Configuration"

    source "init/Kconfig"
    diff --git a/arch/m68knommu/Kconfig b/arch/m68knommu/Kconfig
    index f4b582c..da393c4 100644
    --- a/arch/m68knommu/Kconfig
    +++ b/arch/m68knommu/Kconfig
    @@ -518,6 +518,11 @@ config 4KSTACKS
    running more threads on a system and also reduces the pressure
    on the VM subsystem for higher order allocations.

    +config HZ
    + int
    + default 1000 if CLEOPATRA
    + default 100
    +
    comment "RAM configuration"

    config RAMBASE
    diff --git a/arch/sh64/Kconfig b/arch/sh64/Kconfig
    index 6884d5a..95b76aa 100644
    --- a/arch/sh64/Kconfig
    +++ b/arch/sh64/Kconfig
    @@ -293,3 +293,9 @@ source "security/Kconfig"
    source "crypto/Kconfig"

    source "lib/Kconfig"
    +
    +# Higher frequency needed for high-res WOVF
    +config HZ
    + int
    + default 1000 if SH_WDT
    + default 100
    diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
    index 527adc8..e2991f9 100644
    --- a/arch/sparc/Kconfig
    +++ b/arch/sparc/Kconfig
    @@ -27,6 +27,10 @@ config ARCH_NO_VIRT_TO_BUS
    config OF
    def_bool y

    +config HZ
    + int
    + default 100
    +
    source "init/Kconfig"

    menu "General machine setup"
    diff --git a/arch/v850/Kconfig b/arch/v850/Kconfig
    index b6a50b8..b9c8b54 100644
    --- a/arch/v850/Kconfig
    +++ b/arch/v850/Kconfig
    @@ -212,6 +212,13 @@ menu "Processor type and features"
    bool
    default !V850E_CACHE && !V850E2_CACHE

    + # HZ depends on the platform
    + config HZ
    + int
    + default 24 if V850E_SIM || V850E2_SIM85E2
    + default 122 if V850E2_FPGA85E2C
    + default 100
    +
    #### Misc config

    config ROM_KERNEL
    diff --git a/arch/xtensa/Kconfig b/arch/xtensa/Kconfig
    index d3cb3d6..2a2aff1 100644
    --- a/arch/xtensa/Kconfig
    +++ b/arch/xtensa/Kconfig
    @@ -49,6 +49,10 @@ config ARCH_HAS_ILOG2_U64
    config NO_IOPORT
    def_bool y

    +config HZ
    + int
    + default 100
    +
    source "init/Kconfig"

    menu "Processor type and features"
    diff --git a/include/asm-alpha/param.h b/include/asm-alpha/param.h
    index 214e799..0982f1d 100644
    --- a/include/asm-alpha/param.h
    +++ b/include/asm-alpha/param.h
    @@ -5,15 +5,7 @@
    hardware ignores reprogramming. We also need userland buy-in to the
    change in HZ, since this is visible in the wait4 resources etc. */

    -
    -#ifndef HZ
    -# ifndef CONFIG_ALPHA_RAWHIDE
    -# define HZ 1024
    -# else
    -# define HZ 1200
    -# endif
    -#endif
    -
    +#define HZ CONFIG_HZ
    #define USER_HZ HZ

    #define EXEC_PAGESIZE 8192
    diff --git a/include/asm-cris/param.h b/include/asm-cris/param.h
    index b249726..0e47994 100644
    --- a/include/asm-cris/param.h
    +++ b/include/asm-cris/param.h
    @@ -3,7 +3,7 @@

    /* Currently we assume that HZ=100 is good for CRIS. */
    #ifdef __KERNEL__
    -# define HZ 100 /* Internal kernel timer frequency */
    +# define HZ CONFIG_HZ /* Internal kernel timer frequency */
    # define USER_HZ 100 /* .. some user interfaces are in "ticks" */
    # define CLOCKS_PER_SEC (USER_HZ) /* like times() */
    #endif
    diff --git a/include/asm-frv/param.h b/include/asm-frv/param.h
    index 365653b..6859dd5 100644
    --- a/include/asm-frv/param.h
    +++ b/include/asm-frv/param.h
    @@ -2,7 +2,7 @@
    #define _ASM_PARAM_H

    #ifdef __KERNEL__
    -#define HZ 1000 /* Internal kernel timer frequency */
    +#define HZ CONFIG_HZ /* Internal kernel timer frequency */
    #define USER_HZ 100 /* .. some user interfaces are in "ticks" */
    #define CLOCKS_PER_SEC (USER_HZ) /* like times() */
    #endif
    diff --git a/include/asm-h8300/param.h b/include/asm-h8300/param.h
    index c25806e..04f64f1 100644
    --- a/include/asm-h8300/param.h
    +++ b/include/asm-h8300/param.h
    @@ -3,7 +3,7 @@


    #ifndef HZ
    -#define HZ 100
    +#define HZ CONFIG_HZ
    #endif

    #ifdef __KERNEL__
    diff --git a/include/asm-m32r/param.h b/include/asm-m32r/param.h
    index 3e14026..94c7701 100644
    --- a/include/asm-m32r/param.h
    +++ b/include/asm-m32r/param.h
    @@ -2,7 +2,7 @@
    #define _ASM_M32R_PARAM_H

    #ifdef __KERNEL__
    -# define HZ 100 /* Internal kernel timer frequency */
    +# define HZ CONFIG_HZ /* Internal kernel timer frequency */
    # define USER_HZ 100 /* .. some user interfaces are in "ticks" */
    # define CLOCKS_PER_SEC (USER_HZ) /* like times() */
    #endif
    diff --git a/include/asm-m68k/param.h b/include/asm-m68k/param.h
    index 60f409d..536a278 100644
    --- a/include/asm-m68k/param.h
    +++ b/include/asm-m68k/param.h
    @@ -2,7 +2,7 @@
    #define _M68K_PARAM_H

    #ifdef __KERNEL__
    -# define HZ 100 /* Internal kernel timer frequency */
    +# define HZ CONFIG_HZ /* Internal kernel timer frequency */
    # define USER_HZ 100 /* .. some user interfaces are in "ticks" */
    # define CLOCKS_PER_SEC (USER_HZ) /* like times() */
    #endif
    diff --git a/include/asm-m68knommu/param.h b/include/asm-m68knommu/param.h
    index 4c9904d..96c4510 100644
    --- a/include/asm-m68knommu/param.h
    +++ b/include/asm-m68knommu/param.h
    @@ -1,13 +1,7 @@
    #ifndef _M68KNOMMU_PARAM_H
    #define _M68KNOMMU_PARAM_H

    -
    -#if defined(CONFIG_CLEOPATRA)
    -#define HZ 1000
    -#endif
    -#ifndef HZ
    -#define HZ 100
    -#endif
    +#define HZ CONFIG_HZ

    #ifdef __KERNEL__
    #define USER_HZ HZ
    diff --git a/include/asm-sh64/param.h b/include/asm-sh64/param.h
    index f409adb..4665154 100644
    --- a/include/asm-sh64/param.h
    +++ b/include/asm-sh64/param.h
    @@ -14,11 +14,7 @@


    #ifdef __KERNEL__
    -# ifdef CONFIG_SH_WDT
    -# define HZ 1000 /* Needed for high-res WOVF */
    -# else
    -# define HZ 100
    -# endif
    +# define HZ CONFIG_HZ
    # define USER_HZ 100 /* User interfaces are in "ticks" */
    # define CLOCKS_PER_SEC (USER_HZ) /* frequency at which times() counts */
    #endif
    diff --git a/include/asm-sparc/param.h b/include/asm-sparc/param.h
    index beaf02d..86ba59a 100644
    --- a/include/asm-sparc/param.h
    +++ b/include/asm-sparc/param.h
    @@ -3,7 +3,7 @@
    #define _ASMSPARC_PARAM_H

    #ifdef __KERNEL__
    -# define HZ 100 /* Internal kernel timer frequency */
    +# define HZ CONFIG_HZ /* Internal kernel timer frequency */
    # define USER_HZ 100 /* .. some user interfaces are in "ticks" */
    # define CLOCKS_PER_SEC (USER_HZ)
    #endif
    diff --git a/include/asm-v850/anna.h b/include/asm-v850/anna.h
    index 3be77d5..cd5eaee 100644
    --- a/include/asm-v850/anna.h
    +++ b/include/asm-v850/anna.h
    @@ -134,10 +134,4 @@ extern void anna_uart_pre_configure (unsigned chan,
    #define V850E_TIMER_D_TMCD_CS_MIN 1 /* min 2^1 divider */


    -/* For <asm/param.h> */
    -#ifndef HZ
    -#define HZ 100
    -#endif
    -
    -
    #endif /* __V850_ANNA_H__ */
    diff --git a/include/asm-v850/as85ep1.h b/include/asm-v850/as85ep1.h
    index 659bc91..5a5ca90 100644
    --- a/include/asm-v850/as85ep1.h
    +++ b/include/asm-v850/as85ep1.h
    @@ -149,10 +149,4 @@ extern void as85ep1_uart_pre_configure (unsigned chan,
    #define V850E_TIMER_D_TMCD_CS_MIN 2 /* min 2^2 divider */


    -/* For <asm/param.h> */
    -#ifndef HZ
    -#define HZ 100
    -#endif
    -
    -
    #endif /* __V850_AS85EP1_H__ */
    diff --git a/include/asm-v850/fpga85e2c.h b/include/asm-v850/fpga85e2c.h
    index d32f045..23aae66 100644
    --- a/include/asm-v850/fpga85e2c.h
    +++ b/include/asm-v850/fpga85e2c.h
    @@ -79,10 +79,4 @@ extern char _r0_ram;
    #endif


    -/* For <asm/param.h> */
    -#ifndef HZ
    -#define HZ 122 /* actually, 8.192ms ticks =~ 122.07 */
    -#endif
    -
    -
    #endif /* __V850_FPGA85E2C_H__ */
    diff --git a/include/asm-v850/param.h b/include/asm-v850/param.h
    index 3c65bd5..2818326 100644
    --- a/include/asm-v850/param.h
    +++ b/include/asm-v850/param.h
    @@ -23,8 +23,7 @@
    #define MAXHOSTNAMELEN 64 /* max length of hostname */

    #ifdef __KERNEL__
    -#include <asm/machdep.h> /* For HZ */
    -
    +# define HZ CONFIG_HZ
    # define USER_HZ 100
    # define CLOCKS_PER_SEC USER_HZ
    #endif
    diff --git a/include/asm-v850/rte_cb.h b/include/asm-v850/rte_cb.h
    index e85d261..db9879f 100644
    --- a/include/asm-v850/rte_cb.h
    +++ b/include/asm-v850/rte_cb.h
    @@ -69,12 +69,6 @@
    #endif /* CONFIG_RTE_MB_A_PCI */


    -/* For <asm/param.h> */
    -#ifndef HZ
    -#define HZ 100
    -#endif
    -
    -
    #ifndef __ASSEMBLY__
    extern void rte_cb_early_init (void);
    extern void rte_cb_init_irqs (void);
    diff --git a/include/asm-v850/sim.h b/include/asm-v850/sim.h
    index 10236ab..026932d 100644
    --- a/include/asm-v850/sim.h
    +++ b/include/asm-v850/sim.h
    @@ -40,11 +40,6 @@
    #define R0_RAM_ADDR 0xFFFFF000


    -/* For <asm/param.h> */
    -#ifndef HZ
    -#define HZ 24 /* Minimum supported frequency. */
    -#endif
    -
    /* For <asm/irq.h> */
    #define NUM_CPU_IRQS 6

    diff --git a/include/asm-v850/sim85e2.h b/include/asm-v850/sim85e2.h
    index 17dd4fa..8b4d697 100644
    --- a/include/asm-v850/sim85e2.h
    +++ b/include/asm-v850/sim85e2.h
    @@ -66,10 +66,4 @@
    #define R0_RAM_ADDR 0xFFFFE000


    -/* For <asm/param.h> */
    -#ifndef HZ
    -#define HZ 24 /* Minimum supported frequency. */
    -#endif
    -
    -
    #endif /* __V850_SIM85E2_H__ */
    diff --git a/include/asm-xtensa/param.h b/include/asm-xtensa/param.h
    index ce3a336..82ad34d 100644
    --- a/include/asm-xtensa/param.h
    +++ b/include/asm-xtensa/param.h
    @@ -12,7 +12,7 @@
    #define _XTENSA_PARAM_H

    #ifdef __KERNEL__
    -# define HZ 100 /* internal timer frequency */
    +# define HZ CONFIG_HZ /* internal timer frequency */
    # define USER_HZ 100 /* for user interfaces in "ticks" */
    # define CLOCKS_PER_SEC (USER_HZ) /* frequnzy at which times() counts */
    #endif
    diff --git a/kernel/Makefile b/kernel/Makefile
    index dfa9695..749825a 100644
    --- a/kernel/Makefile
    +++ b/kernel/Makefile
    @@ -80,3 +80,11 @@ quiet_cmd_ikconfiggz = IKCFG $@
    targets += config_data.h
    $(obj)/config_data.h: $(obj)/config_data.gz FORCE
    $(call if_changed,ikconfiggz)
    +
    +$(obj)/time.o: $(obj)/timeconst.h
    +
    +quiet_cmd_timeconst = TIMEC $@
    + cmd_timeconst = $(PERL) $< $(CONFIG_HZ) > $@
    +targets += timeconst.h
    +$(obj)/timeconst.h: $(src)/timeconst.pl $(wildcard include/config/hz.h) FORCE
    + $(call if_changed,timeconst)
    diff --git a/kernel/time.c b/kernel/time.c
    index 09d3c45..8e790b5 100644
    --- a/kernel/time.c
    +++ b/kernel/time.c
    @@ -39,6 +39,8 @@
    #include <asm/uaccess.h>
    #include <asm/unistd.h>

    +#include "timeconst.h"
    +
    /*
    * The timezone where the local system is located. Used as a default by some
    * programs who obtain this value by using gettimeofday.
    @@ -93,7 +95,8 @@ asmlinkage long sys_stime(time_t __user *tptr)

    #endif /* __ARCH_WANT_SYS_TIME */

    -asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __user *tz)
    +asmlinkage long sys_gettimeofday(struct timeval __user *tv,
    + struct timezone __user *tz)
    {
    if (likely(tv != NULL)) {
    struct timeval ktv;
    @@ -118,7 +121,7 @@ asmlinkage long sys_gettimeofday(struct timeval __user *tv, struct timezone __us
    * hard to make the program warp the clock precisely n hours) or
    * compile in the timezone information into the kernel. Bad, bad....
    *
    - * - TYT, 1992-01-01
    + * - TYT, 1992-01-01
    *
    * The best thing to do is to keep the CMOS clock in universal time (UTC)
    * as real UNIX machines always do it. This avoids all headaches about
    @@ -239,7 +242,11 @@ unsigned int inline jiffies_to_msecs(const unsigned long j)
    #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC)
    return (j + (HZ / MSEC_PER_SEC) - 1)/(HZ / MSEC_PER_SEC);
    #else
    - return (j * MSEC_PER_SEC) / HZ;
    +# if BITS_PER_LONG == 32
    + return ((u64)HZ_TO_MSEC_MUL32 * j) >> HZ_TO_MSEC_SHR32;
    +# else
    + return (j * HZ_TO_MSEC_NUM) / HZ_TO_MSEC_DEN;
    +# endif
    #endif
    }
    EXPORT_SYMBOL(jiffies_to_msecs);
    @@ -251,7 +258,11 @@ unsigned int inline jiffies_to_usecs(const unsigned long j)
    #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
    return (j + (HZ / USEC_PER_SEC) - 1)/(HZ / USEC_PER_SEC);
    #else
    - return (j * USEC_PER_SEC) / HZ;
    +# if BITS_PER_LONG == 32
    + return ((u64)HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32;
    +# else
    + return (j * HZ_TO_USEC_NUM) / HZ_TO_USEC_DEN;
    +# endif
    #endif
    }
    EXPORT_SYMBOL(jiffies_to_usecs);
    @@ -351,7 +362,7 @@ EXPORT_SYMBOL(mktime);
    * normalize to the timespec storage format
    *
    * Note: The tv_nsec part is always in the range of
    - * 0 <= tv_nsec < NSEC_PER_SEC
    + * 0 <= tv_nsec < NSEC_PER_SEC
    * For negative values only the tv_sec field is negative !
    */
    void set_normalized_timespec(struct timespec *ts, time_t sec, long nsec)
    @@ -452,12 +463,13 @@ unsigned long msecs_to_jiffies(const unsigned int m)
    /*
    * Generic case - multiply, round and divide. But first
    * check that if we are doing a net multiplication, that
    - * we wouldnt overflow:
    + * we wouldn't overflow:
    */
    if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET))
    return MAX_JIFFY_OFFSET;

    - return (m * HZ + MSEC_PER_SEC - 1) / MSEC_PER_SEC;
    + return ((u64)MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32)
    + >> MSEC_TO_HZ_SHR32;
    #endif
    }
    EXPORT_SYMBOL(msecs_to_jiffies);
    @@ -471,7 +483,8 @@ unsigned long usecs_to_jiffies(const unsigned int u)
    #elif HZ > USEC_PER_SEC && !(HZ % USEC_PER_SEC)
    return u * (HZ / USEC_PER_SEC);
    #else
    - return (u * HZ + USEC_PER_SEC - 1) / USEC_PER_SEC;
    + return ((u64)USEC_TO_HZ_MUL32 * m + USEC_TO_HZ_ADJ32)
    + >> USEC_TO_HZ_SHR32;
    #endif
    }
    EXPORT_SYMBOL(usecs_to_jiffies);
    diff --git a/kernel/timeconst.pl b/kernel/timeconst.pl
    new file mode 100644
    index 0000000..fd46b3d
    --- /dev/null
    +++ b/kernel/timeconst.pl
    @@ -0,0 +1,337 @@
    +#!/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,
    + '0xc49ba5e4','0x1fbe76c8b4',37,
    + '0xc49ba5e353f7ceda','0x1fbe76c8b439581062',69,
    + '0xa2c2aaab','0xaaaa',16,
    + '0xa2c2aaaaaaaaaaab','0xaaaaaaaaaaaa',48,
    + '0xc9539b89','0x7fffbce4217d',47,
    + '0xc9539b8887229e91','0x7fffbce4217d2849cb25',79,
    + ], 32 => [
    + '0xfa000000','0x6000000',27,
    + '0xfa00000000000000','0x600000000000000',59,
    + '0x83126e98','0xfdf3b645a',36,
    + '0x83126e978d4fdf3c','0xfdf3b645a1cac0831',68,
    + '0xf4240000','0x0',17,
    + '0xf424000000000000','0x0',49,
    + '0x8637bd06','0x3fff79c842fa',46,
    + '0x8637bd05af6c69b6','0x3fff79c842fa5093964a',78,
    + ], 48 => [
    + '0xa6aaaaab','0x6aaaaaa',27,
    + '0xa6aaaaaaaaaaaaab','0x6aaaaaaaaaaaaaa',59,
    + '0xc49ba5e4','0xfdf3b645a',36,
    + '0xc49ba5e353f7ceda','0xfdf3b645a1cac0831',68,
    + '0xa2c2aaab','0x15555',17,
    + '0xa2c2aaaaaaaaaaab','0x1555555555555',49,
    + '0xc9539b89','0x3fffbce4217d',46,
    + '0xc9539b8887229e91','0x3fffbce4217d2849cb25',78,
    + ], 64 => [
    + '0xfa000000','0xe000000',28,
    + '0xfa00000000000000','0xe00000000000000',60,
    + '0x83126e98','0x7ef9db22d',35,
    + '0x83126e978d4fdf3c','0x7ef9db22d0e560418',67,
    + '0xf4240000','0x0',18,
    + '0xf424000000000000','0x0',50,
    + '0x8637bd06','0x1fff79c842fa',45,
    + '0x8637bd05af6c69b6','0x1fff79c842fa5093964a',77,
    + ], 100 => [
    + '0xa0000000','0x0',28,
    + '0xa000000000000000','0x0',60,
    + '0xcccccccd','0x733333333',35,
    + '0xcccccccccccccccd','0x73333333333333333',67,
    + '0x9c400000','0x0',18,
    + '0x9c40000000000000','0x0',50,
    + '0xd1b71759','0x1fff2e48e8a7',45,
    + '0xd1b71758e219652c','0x1fff2e48e8a71de69ad4',77,
    + ], 122 => [
    + '0x8325c53f','0xfbcda3a',28,
    + '0x8325c53ef368eb05','0xfbcda3ac10c9714',60,
    + '0xf9db22d1','0x7fbe76c8b',35,
    + '0xf9db22d0e560418a','0x7fbe76c8b43958106',67,
    + '0x8012e2a0','0x3ef36',18,
    + '0x8012e29f79b47583','0x3ef368eb04325',50,
    + '0xffda4053','0x1ffffbce4217',45,
    + '0xffda4052d666a983','0x1ffffbce4217d2849cb2',77,
    + ], 128 => [
    + '0xfa000000','0x1e000000',29,
    + '0xfa00000000000000','0x1e00000000000000',61,
    + '0x83126e98','0x3f7ced916',34,
    + '0x83126e978d4fdf3c','0x3f7ced916872b020c',66,
    + '0xf4240000','0x40000',19,
    + '0xf424000000000000','0x4000000000000',51,
    + '0x8637bd06','0xfffbce4217d',44,
    + '0x8637bd05af6c69b6','0xfffbce4217d2849cb25',76,
    + ], 200 => [
    + '0xa0000000','0x0',29,
    + '0xa000000000000000','0x0',61,
    + '0xcccccccd','0x333333333',34,
    + '0xcccccccccccccccd','0x33333333333333333',66,
    + '0x9c400000','0x0',19,
    + '0x9c40000000000000','0x0',51,
    + '0xd1b71759','0xfff2e48e8a7',44,
    + '0xd1b71758e219652c','0xfff2e48e8a71de69ad4',76,
    + ], 250 => [
    + '0x80000000','0x0',29,
    + '0x8000000000000000','0x0',61,
    + '0x80000000','0x180000000',33,
    + '0x8000000000000000','0x18000000000000000',65,
    + '0xfa000000','0x0',20,
    + '0xfa00000000000000','0x0',52,
    + '0x83126e98','0x7ff7ced9168',43,
    + '0x83126e978d4fdf3c','0x7ff7ced916872b020c4',75,
    + ], 256 => [
    + '0xfa000000','0x3e000000',30,
    + '0xfa00000000000000','0x3e00000000000000',62,
    + '0x83126e98','0x1fbe76c8b',33,
    + '0x83126e978d4fdf3c','0x1fbe76c8b43958106',65,
    + '0xf4240000','0xc0000',20,
    + '0xf424000000000000','0xc000000000000',52,
    + '0x8637bd06','0x7ffde7210be',43,
    + '0x8637bd05af6c69b6','0x7ffde7210be9424e592',75,
    + ], 300 => [
    + '0xd5555556','0x2aaaaaaa',30,
    + '0xd555555555555556','0x2aaaaaaaaaaaaaaa',62,
    + '0x9999999a','0x1cccccccc',33,
    + '0x999999999999999a','0x1cccccccccccccccc',65,
    + '0xd0555556','0xaaaaa',20,
    + '0xd055555555555556','0xaaaaaaaaaaaaa',52,
    + '0x9d495183','0x7ffcb923a29',43,
    + '0x9d495182a9930be1','0x7ffcb923a29c779a6b5',75,
    + ], 512 => [
    + '0xfa000000','0x7e000000',31,
    + '0xfa00000000000000','0x7e00000000000000',63,
    + '0x83126e98','0xfdf3b645',32,
    + '0x83126e978d4fdf3c','0xfdf3b645a1cac083',64,
    + '0xf4240000','0x1c0000',21,
    + '0xf424000000000000','0x1c000000000000',53,
    + '0x8637bd06','0x3ffef39085f',42,
    + '0x8637bd05af6c69b6','0x3ffef39085f4a1272c9',74,
    + ], 1000 => [
    + '0x80000000','0x0',31,
    + '0x8000000000000000','0x0',63,
    + '0x80000000','0x0',31,
    + '0x8000000000000000','0x0',63,
    + '0xfa000000','0x0',22,
    + '0xfa00000000000000','0x0',54,
    + '0x83126e98','0x1ff7ced9168',41,
    + '0x83126e978d4fdf3c','0x1ff7ced916872b020c4',73,
    + ], 1024 => [
    + '0xfa000000','0xfe000000',32,
    + '0xfa00000000000000','0xfe00000000000000',64,
    + '0x83126e98','0x7ef9db22',31,
    + '0x83126e978d4fdf3c','0x7ef9db22d0e56041',63,
    + '0xf4240000','0x3c0000',22,
    + '0xf424000000000000','0x3c000000000000',54,
    + '0x8637bd06','0x1fff79c842f',41,
    + '0x8637bd05af6c69b6','0x1fff79c842fa5093964',73,
    + ], 1200 => [
    + '0xd5555556','0xd5555555',32,
    + '0xd555555555555556','0xd555555555555555',64,
    + '0x9999999a','0x66666666',31,
    + '0x999999999999999a','0x6666666666666666',63,
    + '0xd0555556','0x2aaaaa',22,
    + '0xd055555555555556','0x2aaaaaaaaaaaaa',54,
    + '0x9d495183','0x1ffcb923a29',41,
    + '0x9d495182a9930be1','0x1ffcb923a29c779a6b5',73,
    + ]
    +);
    +
    +$has_bigint = eval 'use Math::BigInt qw(bgcd); 1;';
    +
    +sub bint($)
    +{
    + 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 >= $thres);
    + }
    + return 0;
    +}
    +
    +sub compute_values($) {
    + my($hz) = @_;
    + my @val = ();
    + my $s, $m, $a;
    +
    + if (!$has_bigint) {
    + die "$0: HZ == $hz not canned and Math::BigInt not available\n"
    + }
    +
    + # HZ_TO_MSEC_*32
    + $s = fmuls(32, 1000, $hz);
    + $m = fmul($s, 1000, $hz);
    + $a = fadj($s, 1000, $hz);
    + push(@val, $m->as_hex(), $a->as_hex(), $s);
    +
    + # HZ_TO_MSEC_*64
    + $s = fmuls(64, 1000, $hz);
    + $m = fmul($s, 1000, $hz);
    + $a = fadj($s, 1000, $hz);
    + push(@val, $m->as_hex(), $a->as_hex(), $s);
    +
    + # MSEC_TO_HZ_*32
    + $s = fmuls(32, $hz, 1000);
    + $m = fmul($s, $hz, 1000);
    + $a = fadj($s, $hz, 1000);
    + push(@val, $m->as_hex(), $a->as_hex(), $s);
    +
    + # MSEC_TO_HZ_*64
    + $s = fmuls(64, $hz, 1000);
    + $m = fmul($s, $hz, 1000);
    + $a = fadj($s, $hz, 1000);
    + push(@val, $m->as_hex(), $a->as_hex(), $s);
    +
    + # HZ_TO_USEC_*32
    + $s = fmuls(32, 1000000, $hz);
    + $m = fmul($s, 1000000, $hz);
    + $a = fadj($s, 1000000, $hz);
    + push(@val, $m->as_hex(), $a->as_hex(), $s);
    +
    + # HZ_TO_USEC_*64
    + $s = fmuls(64, 1000000, $hz);
    + $m = fmul($s, 1000000, $hz);
    + $a = fadj($s, 1000000, $hz);
    + push(@val, $m->as_hex(), $a->as_hex(), $s);
    +
    + # USEC_TO_HZ_*32
    + $s = fmuls(32, $hz, 1000000);
    + $m = fmul($s, $hz, 1000000);
    + $a = fadj($s, $hz, 1000000);
    + push(@val, $m->as_hex(), $a->as_hex(), $s);
    +
    + # USEC_TO_HZ_*64
    + $s = fmuls(64, $hz, 1000000);
    + $m = fmul($s, $hz, 1000000);
    + $a = fadj($s, $hz, 1000000);
    + push(@val, $m->as_hex(), $a->as_hex(), $s);
    +
    + return @val;
    +}
    +
    +sub output($@)
    +{
    + 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);
    + }
    + }
    + }
    +
    + 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 $m = shift(@values);
    + my $a = shift(@values);
    + my $s = shift(@values);
    + print "\t\t\'",$m,"\',\'",$a,"\',",$s,",\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;
    --
    1.5.3.4


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      Last update: 2007-12-17 23:33    [W:0.069 / U:0.728 seconds]
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