[PATCH v2 56/70] x86/time: CFI hardening

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Control Flow Integrity schemes use toolchain and optionally hardware support
to help protect against call/jump/return oriented programming attacks.

Use cf_check to annotate function pointer targets for the toolchain.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/hpet.c             |  8 ++++----
 xen/arch/x86/include/asm/hpet.h |  4 ++--
 xen/arch/x86/time.c             | 33 +++++++++++++++++----------------
 3 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/xen/arch/x86/hpet.c b/xen/arch/x86/hpet.c
index dcc9e16693e9..2b00c30d1153 100644
--- a/xen/arch/x86/hpet.c
+++ b/xen/arch/x86/hpet.c
@@ -196,7 +196,7 @@ static void evt_do_broadcast(cpumask_t *mask)
        cpumask_raise_softirq(mask, TIMER_SOFTIRQ);
 }
 
-static void handle_hpet_broadcast(struct hpet_event_channel *ch)
+static void cf_check handle_hpet_broadcast(struct hpet_event_channel *ch)
 {
     cpumask_t mask;
     s_time_t now, next_event;
@@ -553,7 +553,7 @@ static void hpet_detach_channel(unsigned int cpu,
 
 void (*__read_mostly pv_rtc_handler)(uint8_t index, uint8_t value);
 
-static void handle_rtc_once(uint8_t index, uint8_t value)
+static void cf_check handle_rtc_once(uint8_t index, uint8_t value)
 {
     if ( index != RTC_REG_B )
         return;
@@ -566,7 +566,7 @@ static void handle_rtc_once(uint8_t index, uint8_t value)
     }
 }
 
-void __init hpet_broadcast_init(void)
+void __init cf_check hpet_broadcast_init(void)
 {
     u64 hpet_rate = hpet_setup();
     u32 hpet_id, cfg;
@@ -637,7 +637,7 @@ void __init hpet_broadcast_init(void)
         hpet_events->flags = HPET_EVT_LEGACY;
 }
 
-void hpet_broadcast_resume(void)
+void cf_check hpet_broadcast_resume(void)
 {
     u32 cfg;
     unsigned int i, n;
diff --git a/xen/arch/x86/include/asm/hpet.h b/xen/arch/x86/include/asm/hpet.h
index f343fe4740f1..9919f7473071 100644
--- a/xen/arch/x86/include/asm/hpet.h
+++ b/xen/arch/x86/include/asm/hpet.h
@@ -89,8 +89,8 @@ void hpet_disable_legacy_replacement_mode(void);
  * Temporarily use an HPET event counter for timer interrupt handling,
  * rather than using the LAPIC timer. Used for Cx state entry.
  */
-void hpet_broadcast_init(void);
-void hpet_broadcast_resume(void);
+void cf_check hpet_broadcast_init(void);
+void cf_check hpet_broadcast_resume(void);
 void cf_check hpet_broadcast_enter(void);
 void cf_check hpet_broadcast_exit(void);
 int hpet_broadcast_is_available(void);
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index 043be2a8ec1a..2a1758ebb33b 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -309,7 +309,7 @@ static uint64_t adjust_elapsed(uint64_t elapsed, uint32_t 
actual,
  * PLATFORM TIMER 1: PROGRAMMABLE INTERVAL TIMER (LEGACY PIT)
  */
 
-static u64 read_pit_count(void)
+static u64 cf_check read_pit_count(void)
 {
     u16 count16;
     u32 count32;
@@ -328,7 +328,7 @@ static u64 read_pit_count(void)
     return count32;
 }
 
-static s64 __init init_pit(struct platform_timesource *pts)
+static s64 __init cf_check init_pit(struct platform_timesource *pts)
 {
     u8 portb = inb(0x61);
     u64 start, end;
@@ -366,7 +366,7 @@ static s64 __init init_pit(struct platform_timesource *pts)
     return (end - start) * CALIBRATE_FRAC;
 }
 
-static void resume_pit(struct platform_timesource *pts)
+static void cf_check resume_pit(struct platform_timesource *pts)
 {
     /* Set CTC channel 2 to mode 0 again; initial value does not matter. */
     outb(0xb0, PIT_MODE); /* binary, mode 0, LSB/MSB, Ch 2 */
@@ -389,12 +389,12 @@ static struct platform_timesource __initdata plt_pit =
  * PLATFORM TIMER 2: HIGH PRECISION EVENT TIMER (HPET)
  */
 
-static u64 read_hpet_count(void)
+static u64 cf_check read_hpet_count(void)
 {
     return hpet_read32(HPET_COUNTER);
 }
 
-static int64_t __init init_hpet(struct platform_timesource *pts)
+static int64_t __init cf_check init_hpet(struct platform_timesource *pts)
 {
     uint64_t hpet_rate, start;
     uint32_t count, target, elapsed;
@@ -477,7 +477,7 @@ static int64_t __init init_hpet(struct platform_timesource 
*pts)
     return adjust_elapsed(rdtsc_ordered() - start, elapsed, target);
 }
 
-static void resume_hpet(struct platform_timesource *pts)
+static void cf_check resume_hpet(struct platform_timesource *pts)
 {
     hpet_resume(NULL);
 }
@@ -502,12 +502,12 @@ unsigned int __initdata pmtmr_width;
 /* ACPI PM timer ticks at 3.579545 MHz. */
 #define ACPI_PM_FREQUENCY 3579545
 
-static u64 read_pmtimer_count(void)
+static u64 cf_check read_pmtimer_count(void)
 {
     return inl(pmtmr_ioport);
 }
 
-static s64 __init init_pmtimer(struct platform_timesource *pts)
+static s64 __init cf_check init_pmtimer(struct platform_timesource *pts)
 {
     uint64_t start;
     uint32_t count, target, mask, elapsed;
@@ -562,7 +562,7 @@ static unsigned int __initdata tsc_flags;
  * Called in verify_tsc_reliability() under reliable TSC conditions
  * thus reusing all the checks already performed there.
  */
-static s64 __init init_tsc(struct platform_timesource *pts)
+static s64 __init cf_check init_tsc(struct platform_timesource *pts)
 {
     u64 ret = pts->frequency;
 
@@ -584,7 +584,7 @@ static s64 __init init_tsc(struct platform_timesource *pts)
     return ret;
 }
 
-static u64 read_tsc(void)
+static u64 cf_check read_tsc(void)
 {
     return rdtsc_ordered();
 }
@@ -626,7 +626,7 @@ static uint64_t xen_timer_cpu_frequency(void)
     return freq;
 }
 
-static int64_t __init init_xen_timer(struct platform_timesource *pts)
+static int64_t __init cf_check init_xen_timer(struct platform_timesource *pts)
 {
     if ( !xen_guest )
         return 0;
@@ -647,7 +647,7 @@ static always_inline uint64_t read_cycle(const struct 
vcpu_time_info *info,
     return info->system_time + offset;
 }
 
-static uint64_t read_xen_timer(void)
+static uint64_t cf_check read_xen_timer(void)
 {
     struct vcpu_time_info *info = &this_cpu(vcpu_info)->time;
     uint32_t version;
@@ -676,7 +676,7 @@ static uint64_t read_xen_timer(void)
     return ret;
 }
 
-static void resume_xen_timer(struct platform_timesource *pts)
+static void cf_check resume_xen_timer(struct platform_timesource *pts)
 {
     write_atomic(&xen_timer_last, 0);
 }
@@ -702,7 +702,8 @@ static struct platform_timesource __initdata plt_xen_timer =
 static struct ms_hyperv_tsc_page *hyperv_tsc;
 static struct page_info *hyperv_tsc_page;
 
-static int64_t __init init_hyperv_timer(struct platform_timesource *pts)
+static int64_t __init cf_check init_hyperv_timer(
+    struct platform_timesource *pts)
 {
     paddr_t maddr;
     uint64_t tsc_msr, freq;
@@ -745,7 +746,7 @@ static int64_t __init init_hyperv_timer(struct 
platform_timesource *pts)
     return freq;
 }
 
-static uint64_t read_hyperv_timer(void)
+static uint64_t cf_check read_hyperv_timer(void)
 {
     uint64_t scale, ret, tsc;
     int64_t offset;
@@ -1721,7 +1722,7 @@ time_calibration_rendezvous_tail(const struct 
calibration_rendezvous *r,
  * Keep TSCs in sync when they run at the same rate, but may stop in
  * deep-sleep C states.
  */
-static void time_calibration_tsc_rendezvous(void *_r)
+static void cf_check time_calibration_tsc_rendezvous(void *_r)
 {
     int i;
     struct calibration_rendezvous *r = _r;
-- 
2.11.0