x86, vdso: Add 32 bit VDSO time support for 32 bit kernel

This patch add the time support for 32 bit a VDSO to a 32 bit kernel.

For 32 bit programs running on a 32 bit kernel, the same mechanism is
used as for 64 bit programs running on a 64 bit kernel.

Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Stefani Seibold <stefani@seibold.net>
Link: http://lkml.kernel.org/r/1395094933-14252-10-git-send-email-stefani@seibold.net
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

arch/x86/include/asm/vdso.h

@@ -2,6 +2,11 @@
 #define _ASM_X86_VDSO_H
 
 #if defined CONFIG_X86_32 || defined CONFIG_COMPAT
+
+#include <asm/vdso32.h>
+
+extern const char VDSO32_PRELINK[];
+
 /*
  * Given a pointer to the vDSO image, find the pointer to VDSO32_name
  * as that symbol is defined in the vDSO sources or linker script.

arch/x86/include/asm/vdso32.h

@@ -0,0 +1,11 @@
+#ifndef _ASM_X86_VDSO32_H
+#define _ASM_X86_VDSO32_H
+
+#define VDSO_BASE_PAGE	0
+#define VDSO_VVAR_PAGE	1
+#define VDSO_HPET_PAGE	2
+#define VDSO_PAGES	3
+#define VDSO_PREV_PAGES	2
+#define VDSO_OFFSET(x)	((x) * PAGE_SIZE)
+
+#endif

arch/x86/vdso/Makefile

@@ -146,8 +146,16 @@ KBUILD_AFLAGS_32 := $(filter-out -m64,$(KBUILD_AFLAGS))
 $(vdso32-images:%=$(obj)/%.dbg): KBUILD_AFLAGS = $(KBUILD_AFLAGS_32)
 $(vdso32-images:%=$(obj)/%.dbg): asflags-$(CONFIG_X86_64) += -m32
 
+KBUILD_CFLAGS_32 := $(filter-out -m64,$(KBUILD_CFLAGS))
+KBUILD_CFLAGS_32 := $(filter-out -mcmodel=kernel,$(KBUILD_CFLAGS_32))
+KBUILD_CFLAGS_32 := $(filter-out -fno-pic,$(KBUILD_CFLAGS_32))
+KBUILD_CFLAGS_32 := $(filter-out -mfentry,$(KBUILD_CFLAGS_32))
+KBUILD_CFLAGS_32 += -m32 -msoft-float -mregparm=0 -fpic
+$(vdso32-images:%=$(obj)/%.dbg): KBUILD_CFLAGS = $(KBUILD_CFLAGS_32)
+
 $(vdso32-images:%=$(obj)/%.dbg): $(obj)/vdso32-%.so.dbg: FORCE \
 				 $(obj)/vdso32/vdso32.lds \
+				 $(obj)/vdso32/vclock_gettime.o \
 				 $(obj)/vdso32/note.o \
 				 $(obj)/vdso32/%.o
 	$(call if_changed,vdso)

arch/x86/vdso/vclock_gettime.c

@@ -4,6 +4,9 @@
  *
  * Fast user context implementation of clock_gettime, gettimeofday, and time.
  *
+ * 32 Bit compat layer by Stefani Seibold <stefani@seibold.net>
+ *  sponsored by Rohde & Schwarz GmbH & Co. KG Munich/Germany
+ *
  * The code should have no internal unresolved relocations.
  * Check with readelf after changing.
  */
@@ -12,13 +15,11 @@
 #define DISABLE_BRANCH_PROFILING
 
 #include <linux/kernel.h>
-#include <linux/posix-timers.h>
+#include <uapi/linux/time.h>
-#include <linux/time.h>
 #include <linux/string.h>
 #include <asm/vsyscall.h>
 #include <asm/fixmap.h>
 #include <asm/vgtod.h>
-#include <asm/timex.h>
 #include <asm/hpet.h>
 #include <asm/unistd.h>
 #include <asm/io.h>
@@ -26,6 +27,12 @@
 
 #define gtod (&VVAR(vsyscall_gtod_data))
 
+extern int __vdso_clock_gettime(clockid_t clock, struct timespec *ts);
+extern int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz);
+extern time_t __vdso_time(time_t *t);
+
+#ifndef BUILD_VDSO32
+
 static notrace cycle_t vread_hpet(void)
 {
 	return readl((const void __iomem *)fix_to_virt(VSYSCALL_HPET) + HPET_COUNTER);
@@ -118,6 +125,59 @@ static notrace cycle_t vread_pvclock(int *mode)
 }
 #endif
 
+#else
+
+extern u8 hpet_page
+	__attribute__((visibility("hidden")));
+
+#ifdef CONFIG_HPET_TIMER
+static notrace cycle_t vread_hpet(void)
+{
+	return readl((const void __iomem *)(&hpet_page + HPET_COUNTER));
+}
+#endif
+
+notrace static long vdso_fallback_gettime(long clock, struct timespec *ts)
+{
+	long ret;
+
+	asm(
+		"mov %%ebx, %%edx \n"
+		"mov %2, %%ebx \n"
+		"call VDSO32_vsyscall \n"
+		"mov %%edx, %%ebx \n"
+		: "=a" (ret)
+		: "0" (__NR_clock_gettime), "g" (clock), "c" (ts)
+		: "memory", "edx");
+	return ret;
+}
+
+notrace static long vdso_fallback_gtod(struct timeval *tv, struct timezone *tz)
+{
+	long ret;
+
+	asm(
+		"mov %%ebx, %%edx \n"
+		"mov %2, %%ebx \n"
+		"call VDSO32_vsyscall \n"
+		"mov %%edx, %%ebx \n"
+		: "=a" (ret)
+		: "0" (__NR_gettimeofday), "g" (tv), "c" (tz)
+		: "memory", "edx");
+	return ret;
+}
+
+#ifdef CONFIG_PARAVIRT_CLOCK
+
+static notrace cycle_t vread_pvclock(int *mode)
+{
+	*mode = VCLOCK_NONE;
+	return 0;
+}
+#endif
+
+#endif
+
 notrace static cycle_t vread_tsc(void)
 {
 	cycle_t ret;
@@ -131,7 +191,7 @@ notrace static cycle_t vread_tsc(void)
 	 * but no one has ever seen it happen.
 	 */
 	rdtsc_barrier();
-	ret = (cycle_t)vget_cycles();
+	ret = (cycle_t)__native_read_tsc();
 
 	last = gtod->clock.cycle_last;
 
@@ -152,12 +212,14 @@ notrace static cycle_t vread_tsc(void)
 
 notrace static inline u64 vgetsns(int *mode)
 {
-	long v;
+	u64 v;
 	cycles_t cycles;
 	if (gtod->clock.vclock_mode == VCLOCK_TSC)
 		cycles = vread_tsc();
+#ifdef CONFIG_HPET_TIMER
 	else if (gtod->clock.vclock_mode == VCLOCK_HPET)
 		cycles = vread_hpet();
+#endif
 #ifdef CONFIG_PARAVIRT_CLOCK
 	else if (gtod->clock.vclock_mode == VCLOCK_PVCLOCK)
 		cycles = vread_pvclock(mode);
@@ -189,7 +251,7 @@ notrace static int __always_inline do_realtime(struct timespec *ts)
 	return mode;
 }
 
-notrace static int do_monotonic(struct timespec *ts)
+notrace static int __always_inline do_monotonic(struct timespec *ts)
 {
 	unsigned long seq;
 	u64 ns;
@@ -284,7 +346,7 @@ int gettimeofday(struct timeval *, struct timezone *)
  */
 notrace time_t __vdso_time(time_t *t)
 {
-	/* This is atomic on x86_64 so we don't need any locks. */
+	/* This is atomic on x86 so we don't need any locks. */
 	time_t result = ACCESS_ONCE(gtod->wall_time_sec);
 
 	if (t)

arch/x86/vdso/vdso-layout.lds.S

@@ -6,6 +6,24 @@
 
 SECTIONS
 {
+#ifdef BUILD_VDSO32
+#include <asm/vdso32.h>
+
+	.hpet_sect : {
+		hpet_page = . - VDSO_OFFSET(VDSO_HPET_PAGE);
+	} :text :hpet_sect
+
+	.vvar_sect : {
+		vvar = . - VDSO_OFFSET(VDSO_VVAR_PAGE);
+
+	/* Place all vvars at the offsets in asm/vvar.h. */
+#define EMIT_VVAR(name, offset) vvar_ ## name = vvar + offset;
+#define __VVAR_KERNEL_LDS
+#include <asm/vvar.h>
+#undef __VVAR_KERNEL_LDS
+#undef EMIT_VVAR
+	} :text :vvar_sect
+#endif
 	. = SIZEOF_HEADERS;
 
 	.hash		: { *(.hash) }			:text
@@ -61,4 +79,8 @@ PHDRS
 	dynamic		PT_DYNAMIC	FLAGS(4);		/* PF_R */
 	note		PT_NOTE		FLAGS(4);		/* PF_R */
 	eh_frame_hdr	PT_GNU_EH_FRAME;
+#ifdef BUILD_VDSO32
+	vvar_sect	PT_NULL		FLAGS(4);		/* PF_R */
+	hpet_sect	PT_NULL		FLAGS(4);		/* PF_R */
+#endif
 }

arch/x86/vdso/vdso32-setup.c

@@ -25,6 +25,9 @@
 #include <asm/tlbflush.h>
 #include <asm/vdso.h>
 #include <asm/proto.h>
+#include <asm/fixmap.h>
+#include <asm/hpet.h>
+#include <asm/vvar.h>
 
 #ifdef CONFIG_COMPAT_VDSO
 #define VDSO_DEFAULT	0
@@ -141,6 +144,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	struct mm_struct *mm = current->mm;
 	unsigned long addr;
 	int ret = 0;
+	struct vm_area_struct *vma;
 
 #ifdef CONFIG_X86_X32_ABI
 	if (test_thread_flag(TIF_X32))
@@ -163,7 +167,9 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	/*
 	 * MAYWRITE to allow gdb to COW and set breakpoints
 	 */
-	ret = install_special_mapping(mm, addr, PAGE_SIZE,
+	ret = install_special_mapping(mm,
+			addr,
+			VDSO_OFFSET(VDSO_PAGES - VDSO_PREV_PAGES),
 			VM_READ|VM_EXEC|
 			VM_MAYREAD|VM_MAYWRITE|VM_MAYEXEC,
 			vdso32_pages);
@@ -171,6 +177,39 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
 	if (ret)
 		goto up_fail;
 
+	vma = _install_special_mapping(mm,
+			addr -  VDSO_OFFSET(VDSO_PREV_PAGES),
+			VDSO_OFFSET(VDSO_PREV_PAGES),
+			VM_READ,
+			NULL);
+
+	if (IS_ERR(vma)) {
+		ret = PTR_ERR(vma);
+		goto up_fail;
+	}
+
+	ret = remap_pfn_range(vma,
+		addr - VDSO_OFFSET(VDSO_VVAR_PAGE),
+		__pa_symbol(&__vvar_page) >> PAGE_SHIFT,
+		PAGE_SIZE,
+		PAGE_READONLY);
+
+	if (ret)
+		goto up_fail;
+
+#ifdef CONFIG_HPET_TIMER
+	if (hpet_address) {
+		ret = io_remap_pfn_range(vma,
+			addr - VDSO_OFFSET(VDSO_HPET_PAGE),
+			hpet_address >> PAGE_SHIFT,
+			PAGE_SIZE,
+			pgprot_noncached(PAGE_READONLY));
+
+		if (ret)
+			goto up_fail;
+	}
+#endif
+
 	current_thread_info()->sysenter_return =
 		VDSO32_SYMBOL(addr, SYSENTER_RETURN);
 

arch/x86/vdso/vdso32/vclock_gettime.c

@@ -0,0 +1,9 @@
+#define BUILD_VDSO32
+
+#ifndef CONFIG_CC_OPTIMIZE_FOR_SIZE
+#undef CONFIG_OPTIMIZE_INLINING
+#endif
+
+#undef CONFIG_X86_PPRO_FENCE
+
+#include "../vclock_gettime.c"

arch/x86/vdso/vdso32/vdso32.lds.S

@@ -8,6 +8,11 @@
  * values visible using the asm-x86/vdso.h macros from the kernel proper.
  */
 
+#include <asm/page.h>
+
+#define BUILD_VDSO32
+#define VDSO_PRELINK 0
+
 #include "../vdso-layout.lds.S"
 
 /* The ELF entry point can be used to set the AT_SYSINFO value.  */
@@ -23,6 +28,9 @@ VERSION
 		__kernel_vsyscall;
 		__kernel_sigreturn;
 		__kernel_rt_sigreturn;
+		__vdso_clock_gettime;
+		__vdso_gettimeofday;
+		__vdso_time;
 	local: *;
 	};
 }
@@ -33,3 +41,6 @@ VERSION
 VDSO32_vsyscall		= __kernel_vsyscall;
 VDSO32_sigreturn	= __kernel_sigreturn;
 VDSO32_rt_sigreturn	= __kernel_rt_sigreturn;
+VDSO32_clock_gettime	= clock_gettime;
+VDSO32_gettimeofday	= gettimeofday;
+VDSO32_time		= time;