[PATCH 4/5] lib: vsprintf: enable '%*pb[l]' format specifier

[lukas.funke-oss at weidmueller.com]

From: Lukas Funke <lukas.funke at weidmueller.com>

The commit enables vsprintf() to handle the '%*pb[l]' format specifier
in order to print bitmaps and its derivatives such as cpumask and
nodemask [1]. This can be used to derive kernel boot parameters from
bitmaks such as 'isolcpu' or 'nohz_full' [2].

[1] https://www.kernel.org/doc/Documentation/printk-formats.txt
[2] https://www.kernel.org/doc/html/latest/admin-guide/kernel-parameters.html

Signed-off-by: Lukas Funke <lukas.funke at weidmueller.com>
---

 lib/vsprintf.c | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)

diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index e14c6ca9f9..abbd80ea9c 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -25,6 +25,7 @@
 #include <linux/err.h>
 #include <linux/types.h>
 #include <linux/string.h>
+#include <linux/bitmap.h>
 
 /* we use this so that we can do without the ctype library */
 #define is_digit(c)	((c) >= '0' && (c) <= '9')
@@ -390,6 +391,71 @@ static char *ip4_addr_string(char *buf, char *end, u8 *addr, int field_width,
 		      flags & ~SPECIAL);
 }
 
+static char *bitmap_string(char *buf, char *end, const unsigned long *bitmap,
+			   int field_width, int precision, int flags)
+{
+	const int CHUNKSIZE = 32;
+	int nr_bits = max_t(int, field_width, 0);
+	int i, chunksz;
+	int first = 1;
+
+	chunksz = nr_bits & (CHUNKSIZE - 1);
+	if (chunksz == 0)
+		chunksz = CHUNKSIZE;
+
+	i = ALIGN(nr_bits, CHUNKSIZE) - CHUNKSIZE;
+	for (; i >= 0; i -= CHUNKSIZE) {
+		u32 chunkmask, val;
+		int word, bit;
+
+		chunkmask = ((1ULL << chunksz) - 1);
+		word = i / BITS_PER_LONG;
+		bit = i % BITS_PER_LONG;
+		val = (bitmap[word] >> bit) & chunkmask;
+
+		if (!first) {
+			if (buf < end)
+				*buf = ',';
+			buf++;
+		}
+		first = 0;
+
+		field_width = DIV_ROUND_UP(chunksz, 4);
+		buf = number(buf, end, val, 16, field_width, precision,
+			     (SMALL | ZEROPAD));
+
+		chunksz = CHUNKSIZE;
+	}
+	return buf;
+}
+
+static char *bitmap_list_string(char *buf, char *end, unsigned long *addr,
+				int field_width, int precision, int flags)
+{
+	int nr_bits = max_t(int, field_width, 0);
+	int first = 1;
+	int rbot, rtop;
+
+	for_each_set_bitrange(rbot, rtop, addr, nr_bits) {
+		if (!first) {
+			if (buf < end)
+				*buf = ',';
+			buf++;
+		}
+		first = 0;
+
+		buf = number(buf, end, rbot, 10, 0, -1, 0);
+		if (rtop == rbot + 1)
+			continue;
+
+		if (buf < end)
+			*buf = '-';
+		buf = number(++buf, end, rtop - 1, 10, 0, -1, 0);
+	}
+
+	return buf;
+}
+
 #ifdef CONFIG_LIB_UUID
 /*
  * This works (roughly) the same way as Linux's.
@@ -503,6 +569,15 @@ static char *pointer(const char *fmt, char *buf, char *end, void *ptr,
 					       precision, flags);
 		flags &= ~SPECIAL;
 		break;
+	case 'b':
+		switch (fmt[1]) {
+		case 'l':
+			return bitmap_list_string(buf, end, ptr, field_width,
+							precision, flags);
+		default:
+			return bitmap_string(buf, end, ptr, field_width,
+						precision, flags);
+		}
 #ifdef CONFIG_LIB_UUID
 	case 'U':
 		return uuid_string(buf, end, ptr, field_width, precision,
-- 
2.30.2