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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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