sparc: Fix VDSO build with older binutils.

Older versions of bintutils do not allow symbol math across different
segments on sparc:

====================
Assembler messages:
99: Error: operation combines symbols in different segments
====================

This is controlled by whether or not DIFF_EXPR_OK is defined in
gas/config/tc-*.h and for sparc this was not the case until mid-2017.

So we have to patch between %stick and %tick another way.

Do what powerpc does and emit two versions of the relevant functions,
one using %tick and one using %stick, and patch the symbols in the
dynamic symbol table.

Fixes: 2f6c9bf ("sparc: Improve VDSO instruction patching.")
Reported-by: Meelis Roos <mroos@linux.ee>
Tested-by: Meelis Roos <mroos@linux.ee>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/sparc/include/asm/vdso.h

@@ -9,8 +9,6 @@ struct vdso_image {
 	void *data;
 	unsigned long size;   /* Always a multiple of PAGE_SIZE */
 
-	unsigned long tick_patch, tick_patch_len;
-
 	long sym_vvar_start;  /* Negative offset to the vvar area */
 };
 

arch/sparc/vdso/vclock_gettime.c

@@ -90,33 +90,34 @@ notrace static __always_inline u64 vread_tick(void)
 {
 	u64	ret;
 
-	__asm__ __volatile__("1:\n\t"
-			     "rd		%%tick, %0\n\t"
-			     ".pushsection	.tick_patch, \"a\"\n\t"
-			     ".word		1b - ., 1f - .\n\t"
-			     ".popsection\n\t"
-			     ".pushsection	.tick_patch_replacement, \"ax\"\n\t"
-			     "1:\n\t"
-			     "rd		%%asr24, %0\n\t"
-			     ".popsection\n"
-			     : "=r" (ret));
+	__asm__ __volatile__("rd %%tick, %0" : "=r" (ret));
+	return ret;
+}
+
+notrace static __always_inline u64 vread_tick_stick(void)
+{
+	u64	ret;
+
+	__asm__ __volatile__("rd %%asr24, %0" : "=r" (ret));
 	return ret;
 }
 #else
 notrace static __always_inline u64 vread_tick(void)
 {
 	register unsigned long long ret asm("o4");
 
-	__asm__ __volatile__("1:\n\t"
-			     "rd		%%tick, %L0\n\t"
-			     "srlx		%L0, 32, %H0\n\t"
-			     ".pushsection	.tick_patch, \"a\"\n\t"
-			     ".word		1b - ., 1f - .\n\t"
-			     ".popsection\n\t"
-			     ".pushsection	.tick_patch_replacement, \"ax\"\n\t"
-			     "1:\n\t"
-			     "rd		%%asr24, %L0\n\t"
-			     ".popsection\n"
+	__asm__ __volatile__("rd %%tick, %L0\n\t"
+			     "srlx %L0, 32, %H0"
+			     : "=r" (ret));
+	return ret;
+}
+
+notrace static __always_inline u64 vread_tick_stick(void)
+{
+	register unsigned long long ret asm("o4");
+
+	__asm__ __volatile__("rd %%asr24, %L0\n\t"
+			     "srlx %L0, 32, %H0"
 			     : "=r" (ret));
 	return ret;
 }
@@ -132,6 +133,16 @@ notrace static __always_inline u64 vgetsns(struct vvar_data *vvar)
 	return v * vvar->clock.mult;
 }
 
+notrace static __always_inline u64 vgetsns_stick(struct vvar_data *vvar)
+{
+	u64 v;
+	u64 cycles;
+
+	cycles = vread_tick_stick();
+	v = (cycles - vvar->clock.cycle_last) & vvar->clock.mask;
+	return v * vvar->clock.mult;
+}
+
 notrace static __always_inline int do_realtime(struct vvar_data *vvar,
 					       struct timespec *ts)
 {
@@ -152,6 +163,26 @@ notrace static __always_inline int do_realtime(struct vvar_data *vvar,
 	return 0;
 }
 
+notrace static __always_inline int do_realtime_stick(struct vvar_data *vvar,
+						     struct timespec *ts)
+{
+	unsigned long seq;
+	u64 ns;
+
+	do {
+		seq = vvar_read_begin(vvar);
+		ts->tv_sec = vvar->wall_time_sec;
+		ns = vvar->wall_time_snsec;
+		ns += vgetsns_stick(vvar);
+		ns >>= vvar->clock.shift;
+	} while (unlikely(vvar_read_retry(vvar, seq)));
+
+	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
+	ts->tv_nsec = ns;
+
+	return 0;
+}
+
 notrace static __always_inline int do_monotonic(struct vvar_data *vvar,
 						struct timespec *ts)
 {
@@ -172,6 +203,26 @@ notrace static __always_inline int do_monotonic(struct vvar_data *vvar,
 	return 0;
 }
 
+notrace static __always_inline int do_monotonic_stick(struct vvar_data *vvar,
+						      struct timespec *ts)
+{
+	unsigned long seq;
+	u64 ns;
+
+	do {
+		seq = vvar_read_begin(vvar);
+		ts->tv_sec = vvar->monotonic_time_sec;
+		ns = vvar->monotonic_time_snsec;
+		ns += vgetsns_stick(vvar);
+		ns >>= vvar->clock.shift;
+	} while (unlikely(vvar_read_retry(vvar, seq)));
+
+	ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
+	ts->tv_nsec = ns;
+
+	return 0;
+}
+
 notrace static int do_realtime_coarse(struct vvar_data *vvar,
 				      struct timespec *ts)
 {
@@ -227,6 +278,31 @@ int
 clock_gettime(clockid_t, struct timespec *)
 	__attribute__((weak, alias("__vdso_clock_gettime")));
 
+notrace int
+__vdso_clock_gettime_stick(clockid_t clock, struct timespec *ts)
+{
+	struct vvar_data *vvd = get_vvar_data();
+
+	switch (clock) {
+	case CLOCK_REALTIME:
+		if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
+			break;
+		return do_realtime_stick(vvd, ts);
+	case CLOCK_MONOTONIC:
+		if (unlikely(vvd->vclock_mode == VCLOCK_NONE))
+			break;
+		return do_monotonic_stick(vvd, ts);
+	case CLOCK_REALTIME_COARSE:
+		return do_realtime_coarse(vvd, ts);
+	case CLOCK_MONOTONIC_COARSE:
+		return do_monotonic_coarse(vvd, ts);
+	}
+	/*
+	 * Unknown clock ID ? Fall back to the syscall.
+	 */
+	return vdso_fallback_gettime(clock, ts);
+}
+
 notrace int
 __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 {
@@ -262,3 +338,36 @@ __vdso_gettimeofday(struct timeval *tv, struct timezone *tz)
 int
 gettimeofday(struct timeval *, struct timezone *)
 	__attribute__((weak, alias("__vdso_gettimeofday")));
+
+notrace int
+__vdso_gettimeofday_stick(struct timeval *tv, struct timezone *tz)
+{
+	struct vvar_data *vvd = get_vvar_data();
+
+	if (likely(vvd->vclock_mode != VCLOCK_NONE)) {
+		if (likely(tv != NULL)) {
+			union tstv_t {
+				struct timespec ts;
+				struct timeval tv;
+			} *tstv = (union tstv_t *) tv;
+			do_realtime_stick(vvd, &tstv->ts);
+			/*
+			 * Assign before dividing to ensure that the division is
+			 * done in the type of tv_usec, not tv_nsec.
+			 *
+			 * There cannot be > 1 billion usec in a second:
+			 * do_realtime() has already distributed such overflow
+			 * into tv_sec.  So we can assign it to an int safely.
+			 */
+			tstv->tv.tv_usec = tstv->ts.tv_nsec;
+			tstv->tv.tv_usec /= 1000;
+		}
+		if (unlikely(tz != NULL)) {
+			/* Avoid memcpy. Some old compilers fail to inline it */
+			tz->tz_minuteswest = vvd->tz_minuteswest;
+			tz->tz_dsttime = vvd->tz_dsttime;
+		}
+		return 0;
+	}
+	return vdso_fallback_gettimeofday(tv, tz);
+}

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

@@ -73,9 +73,6 @@ SECTIONS
 
 	.text		: { *(.text*) }			:text	=0x90909090,
 
-	.tick_patch 	  : { *(.tick_patch) }		:text
-	.tick_patch_insns : { *(.tick_patch_insns) }	:text
-
 	/DISCARD/ : {
 		*(.discard)
 		*(.discard.*)

arch/sparc/vdso/vdso.lds.S

@@ -18,8 +18,10 @@ VERSION {
 	global:
 		clock_gettime;
 		__vdso_clock_gettime;
+		__vdso_clock_gettime_stick;
 		gettimeofday;
 		__vdso_gettimeofday;
+		__vdso_gettimeofday_stick;
 	local: *;
 	};
 }

arch/sparc/vdso/vdso2c.h

@@ -17,11 +17,9 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
 	unsigned long mapping_size;
 	int i;
 	unsigned long j;
-	ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr, *secstrings_hdr,
-		*patch_sec = NULL;
+	ELF(Shdr) *symtab_hdr = NULL, *strtab_hdr;
 	ELF(Ehdr) *hdr = (ELF(Ehdr) *)raw_addr;
 	ELF(Dyn) *dyn = 0, *dyn_end = 0;
-	const char *secstrings;
 	INT_BITS syms[NSYMS] = {};
 
 	ELF(Phdr) *pt = (ELF(Phdr) *)(raw_addr + GET_BE(&hdr->e_phoff));
@@ -64,18 +62,11 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
 	}
 
 	/* Walk the section table */
-	secstrings_hdr = raw_addr + GET_BE(&hdr->e_shoff) +
-		GET_BE(&hdr->e_shentsize)*GET_BE(&hdr->e_shstrndx);
-	secstrings = raw_addr + GET_BE(&secstrings_hdr->sh_offset);
 	for (i = 0; i < GET_BE(&hdr->e_shnum); i++) {
 		ELF(Shdr) *sh = raw_addr + GET_BE(&hdr->e_shoff) +
 			GET_BE(&hdr->e_shentsize) * i;
 		if (GET_BE(&sh->sh_type) == SHT_SYMTAB)
 			symtab_hdr = sh;
-
-		if (!strcmp(secstrings + GET_BE(&sh->sh_name),
-			    ".tick_patch"))
-			patch_sec = sh;
 	}
 
 	if (!symtab_hdr)
@@ -142,12 +133,6 @@ static void BITSFUNC(go)(void *raw_addr, size_t raw_len,
 	fprintf(outfile, "const struct vdso_image %s_builtin = {\n", name);
 	fprintf(outfile, "\t.data = raw_data,\n");
 	fprintf(outfile, "\t.size = %lu,\n", mapping_size);
-	if (patch_sec) {
-		fprintf(outfile, "\t.tick_patch = %lu,\n",
-			(unsigned long)GET_BE(&patch_sec->sh_offset));
-		fprintf(outfile, "\t.tick_patch_len = %lu,\n",
-			(unsigned long)GET_BE(&patch_sec->sh_size));
-	}
 	for (i = 0; i < NSYMS; i++) {
 		if (required_syms[i].export && syms[i])
 			fprintf(outfile, "\t.sym_%s = %" PRIi64 ",\n",

arch/sparc/vdso/vdso32/vdso32.lds.S

@@ -17,8 +17,10 @@ VERSION {
 	global:
 		clock_gettime;
 		__vdso_clock_gettime;
+		__vdso_clock_gettime_stick;
 		gettimeofday;
 		__vdso_gettimeofday;
+		__vdso_gettimeofday_stick;
 	local: *;
 	};
 }