Commit-ID: ecf9db3d1f1a8fd2c335148891c3b044e9ce0628
Gitweb: https://git.kernel.org/tip/ecf9db3d1f1a8fd2c335148891c3b044e9ce0628
Author: Andy Lutomirski <luto@xxxxxxxxxx>
AuthorDate: Sat, 22 Jun 2019 15:08:18 -0700
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Mon, 24 Jun 2019 01:21:31 +0200
x86/vdso: Give the [ph]vclock_page declarations real types
Clean up the vDSO code a bit by giving pvclock_page and hvclock_page
their actual types instead of u8[PAGE_SIZE]. This shouldn't
materially affect the generated code.
Heavily based on a patch from Linus.
[ tglx: Adapted to the unified VDSO code ]
Co-developed-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: https://lkml.kernel.org/r/6920c5188f8658001af1fc56fd35b815706d300c.1561241273.git.luto@xxxxxxxxxx
---
arch/x86/include/asm/vdso/gettimeofday.h | 36 +++++++++++++++++++++-----------
1 file changed, 24 insertions(+), 12 deletions(-)
diff --git a/arch/x86/include/asm/vdso/gettimeofday.h b/arch/x86/include/asm/vdso/gettimeofday.h
index f92752d6cbcf..5b63f1f78a1f 100644
--- a/arch/x86/include/asm/vdso/gettimeofday.h
+++ b/arch/x86/include/asm/vdso/gettimeofday.h
@@ -26,13 +26,33 @@
#define VDSO_HAS_CLOCK_GETRES 1
+/*
+ * Declare the memory-mapped vclock data pages. These come from hypervisors.
+ * If we ever reintroduce something like direct access to an MMIO clock like
+ * the HPET again, it will go here as well.
+ *
+ * A load from any of these pages will segfault if the clock in question is
+ * disabled, so appropriate compiler barriers and checks need to be used
+ * to prevent stray loads.
+ *
+ * These declarations MUST NOT be const. The compiler will assume that
+ * an extern const variable has genuinely constant contents, and the
+ * resulting code won't work, since the whole point is that these pages
+ * change over time, possibly while we're accessing them.
+ */
+
#ifdef CONFIG_PARAVIRT_CLOCK
-extern u8 pvclock_page[PAGE_SIZE]
+/*
+ * This is the vCPU 0 pvclock page. We only use pvclock from the vDSO
+ * if the hypervisor tells us that all vCPUs can get valid data from the
+ * vCPU 0 page.
+ */
+extern struct pvclock_vsyscall_time_info pvclock_page
__attribute__((visibility("hidden")));
#endif
#ifdef CONFIG_HYPERV_TSCPAGE
-extern u8 hvclock_page[PAGE_SIZE]
+extern struct ms_hyperv_tsc_page hvclock_page
__attribute__((visibility("hidden")));
#endif
@@ -131,14 +151,9 @@ clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
#endif
#ifdef CONFIG_PARAVIRT_CLOCK
-static const struct pvclock_vsyscall_time_info *get_pvti0(void)
-{
- return (const struct pvclock_vsyscall_time_info *)&pvclock_page;
-}
-
static u64 vread_pvclock(void)
{
- const struct pvclock_vcpu_time_info *pvti = &get_pvti0()->pvti;
+ const struct pvclock_vcpu_time_info *pvti = &pvclock_page.pvti;
u32 version;
u64 ret;
@@ -180,10 +195,7 @@ static u64 vread_pvclock(void)
#ifdef CONFIG_HYPERV_TSCPAGE
static u64 vread_hvclock(void)
{
- const struct ms_hyperv_tsc_page *tsc_pg =
- (const struct ms_hyperv_tsc_page *)&hvclock_page;
-
- return hv_read_tsc_page(tsc_pg);
+ return hv_read_tsc_page(&hvclock_page);
}
#endif
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