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    SubjectRe: [PATCH 22/23] sysctl arm: Remove binary sysctl support
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    Russell King <rmk+lkml@arm.linux.org.uk> writes:

    > On Sun, Nov 08, 2009 at 02:45:36PM -0800, Eric W. Biederman wrote:
    >> Russell King <rmk+lkml@arm.linux.org.uk> writes:
    >>
    >> >
    >> > NAK. Glibc uses these numeric sysctls to support ioperm emulation on ARM.
    >> > Therefore, removal of these numeric sysctls breaks that user interface:
    >> >
    >> > static int iobase_name[] = { CTL_BUS, BUS_ISA, BUS_ISA_PORT_BASE };
    >> > static int ioshift_name[] = { CTL_BUS, BUS_ISA, BUS_ISA_PORT_SHIFT };
    >> > if (! sysctl (iobase_name, 3, &io.io_base, &len, NULL, 0)
    >> > && ! sysctl (ioshift_name, 3, &io.shift, &len, NULL, 0))
    >> > {
    >> > io.initdone = 1;
    >> > return 0;
    >> > }
    >>
    >> Those still exist in sysctl_binary.c are provided by reading
    >> /proc/sys/bus/isa/membase, /proc/sys/bus/isa/portbase, and
    >> /proc/sys/bus/isa/portshift.
    >>
    >> The practical difference is that /proc support now must be compiled
    >> in to support sys_sysctl.
    >
    > Have you checked whether glibc supports reading these from procfs rather
    > than sysfs using the code as it stands above?
    >
    > If not, continued NAK due to user visible ABI change which will cause
    > breakage.

    There is not a user visible ABI change. Just a massive implementation change.
    The only user visible change is that CONFIG_SYS_SYSCALL now depends on
    CONFIG_PROC_SYSCTL.

    The implementation of sys_sysctl in binary_sysctl.c will now read
    /proc/sys/bus/isa/portbase and using vfs_read convert the text string
    to a binary integer and return it to glibc in the form sys_sysctl has
    always used.

    And yes, as of glibc-ports-10.1 the arm implementation of ioperm still
    depends on the binary sys_sysctl implementation to get this information.

    Eric


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