[PATCH 4/4] Add 32 bit VDSO time support for 64 bit kernel

stefani
2014-02-01T15:31:59Z

From: Stefani Seibold <stefani@seibold.net>

This patch add the VDSO time support for the IA32 Emulation Layer.

Due the nature of the kernel headers and the LP64 compiler where the
size of a long and a pointer differs against a 32 bit compiler, there
is a lot of type hacking necessary.

This kind of type hacking could be prevent in the future by doing a call to the
64 bit code by the following sequence:

- Compile the arch/x86/vdso/vclock_gettime.c as 64 bit, but only generate
the assembler output.
- Next compile a 32 bit object by including the 64 bit vclock_gettime.s
prefixed with .code64
- At least we need a trampolin code which invokes the 64 bit code and do
the API conversation (64 bit longs to 32 bit longs), like the
followig snipped:

ENTRY(call64)
push %ebp
movl %esp, %ebp
ljmp $__USER_CS, $1f
.code64
1:
andq -0x10, %rsp
movl $__USER_DS, %ecx
movl %ecx, %ds
movl %ecx, %ss
movl %ecx, %es
call *%rax
movl $__USER32_DS, %ecx
movl %ecx, %ds
movl %ecx, %ss
movl %ecx, %es
leaq ret32(%rip), %rdx
movl $__USER32_CS, %ecx
salq $32, %rcx
leaq (%rcx, %rdx), %rcx
push %rcx
ljmp *(%esp)
.code32
ret32:
movl %ebp, %esp
pop %ebp
ret

.code32
ENTRY(gettimeofday32)
push %edi
movl gettimeofday64, %eax
movl 16(%esp), %edi
call call64
pop %edi
ret

Signed-off-by: Stefani Seibold <stefani@seibold.net>
---
arch/x86/vdso/vclock_gettime.c | 112 ++++++++++++++++++++++++++--------
arch/x86/vdso/vdso32/vclock_gettime.c | 7 +++
2 files changed, 95 insertions(+), 24 deletions(-)

diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c
index d163bb5..53eea37 100644
--- a/arch/x86/vdso/vclock_gettime.c
+++ b/arch/x86/vdso/vclock_gettime.c
@@ -31,12 +31,24 @@

#define gtod (&VVAR(vsyscall_gtod_data))

+struct api_timeval {
+ long tv_sec; /* seconds */
+ long tv_usec; /* microseconds */
+};
+
+struct api_timespec {
+ long tv_sec; /* seconds */
+ long tv_nsec; /* microseconds */
+};
+
+typedef long api_time_t;
+
static notrace cycle_t vread_hpet(void)
{
return readl((const void __iomem *)fix_to_virt(VSYSCALL_HPET) + HPET_COUNTER);
}

-notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
+notrace static long vdso_fallback_gettime(long clock, struct api_timespec *ts)
{
long ret;
asm("syscall" : "=a" (ret) :
@@ -44,7 +56,8 @@ notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
return ret;
}

-notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
+notrace static long vdso_fallback_gtod(struct api_timeval *tv,
+ struct timezone *tz)
{
long ret;

@@ -54,20 +67,68 @@ notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
}
#else

+#ifdef CONFIG_IA32_EMULATION
+typedef s64 arch_time_t;
+
+struct arch_timespec {
+ s64 tv_sec;
+ s64 tv_nsec;
+};
+
+#define ALIGN8 __attribute__ ((aligned (8)))
+
+struct arch_vsyscall_gtod_data {
+ seqcount_t seq ALIGN8;
+
+ struct { /* extract of a clocksource struct */
+ int vclock_mode ALIGN8;
+ cycle_t cycle_last ALIGN8;
+ cycle_t mask ALIGN8;
+ u32 mult;
+ u32 shift;
+ } clock;
+
+ /* open coded 'struct timespec' */
+ arch_time_t wall_time_sec;
+ u64 wall_time_snsec;
+ u64 monotonic_time_snsec;
+ arch_time_t monotonic_time_sec;
+
+ struct timezone sys_tz;
+ struct arch_timespec wall_time_coarse;
+ struct arch_timespec monotonic_time_coarse;
+};
+
+struct arch_vsyscall_gtod_data vvar_vsyscall_gtod_data
+ __attribute__((visibility("hidden")));
+#else
struct vsyscall_gtod_data vvar_vsyscall_gtod_data
__attribute__((visibility("hidden")));
+#endif

u32 hpet_counter
__attribute__((visibility("hidden")));

#define gtod (&vvar_vsyscall_gtod_data)

+struct api_timeval {
+ s32 tv_sec; /* seconds */
+ s32 tv_usec; /* microseconds */
+};
+
+struct api_timespec {
+ s32 tv_sec; /* seconds */
+ s32 tv_nsec; /* microseconds */
+};
+
+typedef s32 api_time_t;
+
static notrace cycle_t vread_hpet(void)
{
return readl(&hpet_counter);
}

-notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
+notrace static long vdso_fallback_gettime(long clock, struct api_timespec *ts)
{
long ret;

@@ -77,12 +138,12 @@ notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
"call VDSO32_vsyscall \n"
"pop %%ebx \n"
: "=a" (ret)
- : "0" (__NR_clock_gettime), "d" (clock), "c" (ts)
+ : "0" (__NR_ia32_clock_gettime), "d" (clock), "c" (ts)
: "memory");
return ret;
}

-notrace static long vdso_fallback_gtod(struct timeval *tv,
+notrace static long vdso_fallback_gtod(struct api_timeval *tv,
struct timezone *tz)
{
long ret;
@@ -93,7 +154,7 @@ notrace static long vdso_fallback_gtod(struct timeval *tv,
"call VDSO32_vsyscall \n"
"pop %%ebx \n"
: "=a" (ret)
- : "0" (__NR_gettimeofday), "d" (tv), "c" (tz)
+ : "0" (__NR_ia32_gettimeofday), "d" (tv), "c" (tz)
: "memory");
return ret;
}
@@ -280,43 +341,48 @@ notrace static void do_monotonic_coarse(struct timespec *ts)
} while (unlikely(read_seqcount_retry(&gtod->seq, seq)));
}

-notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
+notrace int __vdso_clock_gettime(clockid_t clock, struct api_timespec *ts)
{
+ struct timespec tmp;
+
switch (clock) {
case CLOCK_REALTIME:
- if (do_realtime(ts) == VCLOCK_NONE)
+ if (do_realtime(&tmp) == VCLOCK_NONE)
goto fallback;
break;
case CLOCK_MONOTONIC:
- if (do_monotonic(ts) == VCLOCK_NONE)
+ if (do_monotonic(&tmp) == VCLOCK_NONE)
goto fallback;
break;
case CLOCK_REALTIME_COARSE:
- do_realtime_coarse(ts);
+ do_realtime_coarse(&tmp);
break;
case CLOCK_MONOTONIC_COARSE:
- do_monotonic_coarse(ts);
+ do_monotonic_coarse(&tmp);
break;
default:
goto fallback;
}

+ ts->tv_sec = tmp.tv_sec;
+ ts->tv_nsec = tmp.tv_nsec;
+
return 0;
fallback:
return vdso_fallback_gettime(clock, ts);
}
-int clock_gettime(clockid_t, struct timespec *)
+int clock_gettime(clockid_t, struct api_timespec *)
__attribute__((weak, alias("__vdso_clock_gettime")));

-notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
+notrace int __vdso_gettimeofday(struct api_timeval *tv, struct timezone *tz)
{
- long ret = VCLOCK_NONE;
+ struct timespec tmp;

if (likely(tv != NULL)) {
- BUILD_BUG_ON(offsetof(struct timeval, tv_usec) !=
- offsetof(struct timespec, tv_nsec) ||
- sizeof(*tv) != sizeof(struct timespec));
- ret = do_realtime((struct timespec *)tv);
+ if (do_realtime(&tmp) == VCLOCK_NONE)
+ return vdso_fallback_gtod(tv, tz);
+ tv->tv_sec = tmp.tv_sec;
+ tv->tv_usec = tmp.tv_nsec;
tv->tv_usec /= 1000;
}
if (unlikely(tz != NULL)) {
@@ -325,25 +391,23 @@ notrace int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
tz->tz_dsttime = gtod->sys_tz.tz_dsttime;
}

- if (ret == VCLOCK_NONE)
- return vdso_fallback_gtod(tv, tz);
return 0;
}
-int gettimeofday(struct timeval *, struct timezone *)
+int gettimeofday(struct api_timeval *, struct timezone *)
__attribute__((weak, alias("__vdso_gettimeofday")));

/*
* This will break when the xtime seconds get inaccurate, but that is
* unlikely
*/
-notrace time_t __vdso_time(time_t *t)
+notrace api_time_t __vdso_time(api_time_t *t)
{
/* This is atomic on x86 so we don't need any locks. */
- time_t result = ACCESS_ONCE(gtod->wall_time_sec);
+ api_time_t result = ACCESS_ONCE(gtod->wall_time_sec);

if (t)
*t = result;
return result;
}
-int time(time_t *t)
+int time(api_time_t *t)
__attribute__((weak, alias("__vdso_time")));
diff --git a/arch/x86/vdso/vdso32/vclock_gettime.c b/arch/x86/vdso/vdso32/vclock_gettime.c
index fab4ec6..b6df952 100644
--- a/arch/x86/vdso/vdso32/vclock_gettime.c
+++ b/arch/x86/vdso/vdso32/vclock_gettime.c
@@ -2,6 +2,8 @@

#ifdef CONFIG_X86_64

+#include <generated/asm/unistd_32_ia32.h>
+
#define _ASM_X86_PAGE_H

#define __pa(x) 0
@@ -10,6 +12,11 @@
#undef CONFIG_ILLEGAL_POINTER_VALUE
#define CONFIG_ILLEGAL_POINTER_VALUE 0

+#else
+
+#define __NR_ia32_clock_gettime __NR_clock_gettime
+#define __NR_ia32_gettimeofday __NR_gettimeofday
+
#endif

#include "../vclock_gettime.c"
--
1.8.5.3