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    SubjectRe: More breakage in native_rdtsc out of line in git-x86

    * Andi Kleen <andi@firstfloor.org> wrote:

    > Unfortunately simply adding __vsyscall_fn to native_read_tsc doesn't
    > work -- causes early kernel faults like
    >
    > PANIC: early exception rip ffffffffff600105 error 10 cr2 ffffffffff600105
    > Pid: 0, comm: swapper Not tainted 2.6.24-rc6 #58
    >
    > Call Trace:
    > [<ffffffff80211dec>] native_sched_clock+0x9/0x3f
    > [<ffffffff8022b758>] init_idle+0x33/0xd1
    > [<ffffffff80825449>] sched_init+0x26d/0x283
    > [<ffffffff80815899>] start_kernel+0x10b/0x2bd
    > [<ffffffff80815114>] _sinittext+0x114/0x11b
    >
    > Not sure why that is -- in theory the vsyscall functions should be
    > callable from the main kernel. Might be a binutils problem or another
    > code regression.

    nope, it's a 64-bit setup/dependency bug/problem: the vsyscall mappings
    are installed via an __initcall, and that's too late for early use. The
    combo patch below fixed the crash for me, does it work on your box too?

    Ingo

    Index: linux-x86.q/arch/x86/kernel/rtc.c
    ===================================================================
    --- linux-x86.q.orig/arch/x86/kernel/rtc.c
    +++ linux-x86.q/arch/x86/kernel/rtc.c
    @@ -195,7 +195,7 @@ int update_persistent_clock(struct times
    return set_rtc_mmss(now.tv_sec);
    }

    -unsigned long long native_read_tsc(void)
    +unsigned long long __vsyscall_fn native_read_tsc(void)
    {
    DECLARE_ARGS(val, low, high);

    Index: linux-x86.q/arch/x86/kernel/setup_64.c
    ===================================================================
    --- linux-x86.q.orig/arch/x86/kernel/setup_64.c
    +++ linux-x86.q/arch/x86/kernel/setup_64.c
    @@ -46,6 +46,7 @@
    #include <asm/mtrr.h>
    #include <asm/uaccess.h>
    #include <asm/system.h>
    +#include <asm/vsyscall.h>
    #include <asm/io.h>
    #include <asm/smp.h>
    #include <asm/msr.h>
    @@ -464,6 +465,7 @@ void __init setup_arch(char **cmdline_p)
    #endif
    reserve_crashkernel();
    paging_init();
    + map_vsyscall();

    early_quirks();

    Index: linux-x86.q/arch/x86/kernel/vsyscall_64.c
    ===================================================================
    --- linux-x86.q.orig/arch/x86/kernel/vsyscall_64.c
    +++ linux-x86.q/arch/x86/kernel/vsyscall_64.c
    @@ -319,7 +319,7 @@ cpu_vsyscall_notifier(struct notifier_bl
    return NOTIFY_DONE;
    }

    -static void __init map_vsyscall(void)
    +void __init map_vsyscall(void)
    {
    extern char __vsyscall_0;
    unsigned long physaddr_page0 = __pa_symbol(&__vsyscall_0);
    @@ -335,7 +335,6 @@ static int __init vsyscall_init(void)
    BUG_ON((unsigned long) &vtime != VSYSCALL_ADDR(__NR_vtime));
    BUG_ON((VSYSCALL_ADDR(0) != __fix_to_virt(VSYSCALL_FIRST_PAGE)));
    BUG_ON((unsigned long) &vgetcpu != VSYSCALL_ADDR(__NR_vgetcpu));
    - map_vsyscall();
    #ifdef CONFIG_SYSCTL
    register_sysctl_table(kernel_root_table2);
    #endif

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