X-Git-Url: http://v3vee.org/palacios/gitweb/gitweb.cgi?a=blobdiff_plain;f=kitten%2Farch%2Fx86_64%2Flib%2Fbitops.c;fp=kitten%2Farch%2Fx86_64%2Flib%2Fbitops.c;h=ae58ed7ecc74f36ddf650497c5b46f8d5a25ba58;hb=66a1a4c7a9edcd7d8bc207aca093d694a6e6b5b2;hp=0000000000000000000000000000000000000000;hpb=f7cf9c19ecb0a589dd45ae0d2c91814bd3c2acc2;p=palacios-OLD.git

diff --git a/kitten/arch/x86_64/lib/bitops.c b/kitten/arch/x86_64/lib/bitops.c
new file mode 100644
index 0000000..ae58ed7
--- /dev/null
+++ b/kitten/arch/x86_64/lib/bitops.c
@@ -0,0 +1,175 @@
+#include <lwk/bitops.h>
+
+#undef find_first_zero_bit
+#undef find_next_zero_bit
+#undef find_first_bit
+#undef find_next_bit
+
+static inline long
+__find_first_zero_bit(const unsigned long * addr, unsigned long size)
+{
+	long d0, d1, d2;
+	long res;
+
+	/*
+	 * We must test the size in words, not in bits, because
+	 * otherwise incoming sizes in the range -63..-1 will not run
+	 * any scasq instructions, and then the flags used by the je
+	 * instruction will have whatever random value was in place
+	 * before.  Nobody should call us like that, but
+	 * find_next_zero_bit() does when offset and size are at the
+	 * same word and it fails to find a zero itself.
+	 */
+	size += 63;
+	size >>= 6;
+	if (!size)
+		return 0;
+	asm volatile(
+		"  repe; scasq\n"
+		"  je 1f\n"
+		"  xorq -8(%%rdi),%%rax\n"
+		"  subq $8,%%rdi\n"
+		"  bsfq %%rax,%%rdx\n"
+		"1:  subq %[addr],%%rdi\n"
+		"  shlq $3,%%rdi\n"
+		"  addq %%rdi,%%rdx"
+		:"=d" (res), "=&c" (d0), "=&D" (d1), "=&a" (d2)
+		:"0" (0ULL), "1" (size), "2" (addr), "3" (-1ULL),
+		 [addr] "S" (addr) : "memory");
+	/*
+	 * Any register would do for [addr] above, but GCC tends to
+	 * prefer rbx over rsi, even though rsi is readily available
+	 * and doesn't have to be saved.
+	 */
+	return res;
+}
+
+/**
+ * find_first_zero_bit - find the first zero bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The maximum size to search
+ *
+ * Returns the bit-number of the first zero bit, not the number of the byte
+ * containing a bit.
+ */
+long find_first_zero_bit(const unsigned long * addr, unsigned long size)
+{
+	return __find_first_zero_bit (addr, size);
+}
+
+/**
+ * find_next_zero_bit - find the first zero bit in a memory region
+ * @addr: The address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The maximum size to search
+ */
+long find_next_zero_bit (const unsigned long * addr, long size, long offset)
+{
+	const unsigned long * p = addr + (offset >> 6);
+	unsigned long set = 0;
+	unsigned long res, bit = offset&63;
+
+	if (bit) {
+		/*
+		 * Look for zero in first word
+		 */
+		asm("bsfq %1,%0\n\t"
+		    "cmoveq %2,%0"
+		    : "=r" (set)
+		    : "r" (~(*p >> bit)), "r"(64L));
+		if (set < (64 - bit))
+			return set + offset;
+		set = 64 - bit;
+		p++;
+	}
+	/*
+	 * No zero yet, search remaining full words for a zero
+	 */
+	res = __find_first_zero_bit (p, size - 64 * (p - addr));
+
+	return (offset + set + res);
+}
+
+static inline long
+__find_first_bit(const unsigned long * addr, unsigned long size)
+{
+	long d0, d1;
+	long res;
+
+	/*
+	 * We must test the size in words, not in bits, because
+	 * otherwise incoming sizes in the range -63..-1 will not run
+	 * any scasq instructions, and then the flags used by the jz
+	 * instruction will have whatever random value was in place
+	 * before.  Nobody should call us like that, but
+	 * find_next_bit() does when offset and size are at the same
+	 * word and it fails to find a one itself.
+	 */
+	size += 63;
+	size >>= 6;
+	if (!size)
+		return 0;
+	asm volatile(
+		"   repe; scasq\n"
+		"   jz 1f\n"
+		"   subq $8,%%rdi\n"
+		"   bsfq (%%rdi),%%rax\n"
+		"1: subq %[addr],%%rdi\n"
+		"   shlq $3,%%rdi\n"
+		"   addq %%rdi,%%rax"
+		:"=a" (res), "=&c" (d0), "=&D" (d1)
+		:"0" (0ULL), "1" (size), "2" (addr),
+		 [addr] "r" (addr) : "memory");
+	return res;
+}
+
+/**
+ * find_first_bit - find the first set bit in a memory region
+ * @addr: The address to start the search at
+ * @size: The maximum size to search
+ *
+ * Returns the bit-number of the first set bit, not the number of the byte
+ * containing a bit.
+ */
+long find_first_bit(const unsigned long * addr, unsigned long size)
+{
+	return __find_first_bit(addr,size);
+}
+
+/**
+ * find_next_bit - find the first set bit in a memory region
+ * @addr: The address to base the search on
+ * @offset: The bitnumber to start searching at
+ * @size: The maximum size to search
+ */
+long find_next_bit(const unsigned long * addr, long size, long offset)
+{
+	const unsigned long * p = addr + (offset >> 6);
+	unsigned long set = 0, bit = offset & 63, res;
+
+	if (bit) {
+		/*
+		 * Look for nonzero in the first 64 bits:
+		 */
+		asm("bsfq %1,%0\n\t"
+		    "cmoveq %2,%0\n\t"
+		    : "=r" (set)
+		    : "r" (*p >> bit), "r" (64L));
+		if (set < (64 - bit))
+			return set + offset;
+		set = 64 - bit;
+		p++;
+	}
+	/*
+	 * No set bit yet, search remaining full words for a bit
+	 */
+	res = __find_first_bit (p, size - 64 * (p - addr));
+	return (offset + set + res);
+}
+
+#include <lwk/linux_compat.h>
+
+EXPORT_SYMBOL(find_next_bit);
+EXPORT_SYMBOL(find_first_bit);
+EXPORT_SYMBOL(find_first_zero_bit);
+EXPORT_SYMBOL(find_next_zero_bit);