[PATCH v4 05/34] KVM: selftests: Add guest_snprintf() to KVM selftests
Sean Christopherson
seanjc at google.com
Fri Jul 28 17:36:14 PDT 2023
From: Aaron Lewis <aaronlewis at google.com>
Add a local version of guest_snprintf() for use in the guest.
Having a local copy allows the guest access to string formatting
options without dependencies on LIBC. LIBC is problematic because
it heavily relies on both AVX-512 instructions and a TLS, neither of
which are guaranteed to be set up in the guest.
The file guest_sprintf.c was lifted from arch/x86/boot/printf.c and
adapted to work in the guest, including the addition of buffer length.
I.e. s/sprintf/snprintf/
The functions where prefixed with "guest_" to allow guests to
explicitly call them.
A string formatted by this function is expected to succeed or die. If
something goes wrong during the formatting process a GUEST_ASSERT()
will be thrown.
Signed-off-by: Aaron Lewis <aaronlewis at google.com>
Link: https://lore.kernel.org/all/mtdi6smhur5rqffvpu7qux7mptonw223y2653x2nwzvgm72nlo@zyc4w3kwl3rg
[sean: add a link to the discussion of other options]
Signed-off-by: Sean Christopherson <seanjc at google.com>
---
tools/testing/selftests/kvm/Makefile | 1 +
.../testing/selftests/kvm/include/test_util.h | 3 +
.../testing/selftests/kvm/lib/guest_sprintf.c | 307 ++++++++++++++++++
3 files changed, 311 insertions(+)
create mode 100644 tools/testing/selftests/kvm/lib/guest_sprintf.c
diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
index f6c14ab476ac..f65889f5a083 100644
--- a/tools/testing/selftests/kvm/Makefile
+++ b/tools/testing/selftests/kvm/Makefile
@@ -23,6 +23,7 @@ LIBKVM += lib/guest_modes.c
LIBKVM += lib/io.c
LIBKVM += lib/kvm_util.c
LIBKVM += lib/memstress.c
+LIBKVM += lib/guest_sprintf.c
LIBKVM += lib/rbtree.c
LIBKVM += lib/sparsebit.c
LIBKVM += lib/test_util.c
diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index a4bea44f990c..7a5907da1719 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -185,4 +185,7 @@ static inline uint32_t atoi_non_negative(const char *name, const char *num_str)
return num;
}
+int guest_vsnprintf(char *buf, int n, const char *fmt, va_list args);
+int guest_snprintf(char *buf, int n, const char *fmt, ...);
+
#endif /* SELFTEST_KVM_TEST_UTIL_H */
diff --git a/tools/testing/selftests/kvm/lib/guest_sprintf.c b/tools/testing/selftests/kvm/lib/guest_sprintf.c
new file mode 100644
index 000000000000..c4a69d8aeb68
--- /dev/null
+++ b/tools/testing/selftests/kvm/lib/guest_sprintf.c
@@ -0,0 +1,307 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include "test_util.h"
+#include "kvm_util.h"
+#include "ucall_common.h"
+
+#define APPEND_BUFFER_SAFE(str, end, v) \
+do { \
+ GUEST_ASSERT(str < end); \
+ *str++ = (v); \
+} while (0)
+
+static int isdigit(int ch)
+{
+ return (ch >= '0') && (ch <= '9');
+}
+
+static int skip_atoi(const char **s)
+{
+ int i = 0;
+
+ while (isdigit(**s))
+ i = i * 10 + *((*s)++) - '0';
+ return i;
+}
+
+#define ZEROPAD 1 /* pad with zero */
+#define SIGN 2 /* unsigned/signed long */
+#define PLUS 4 /* show plus */
+#define SPACE 8 /* space if plus */
+#define LEFT 16 /* left justified */
+#define SMALL 32 /* Must be 32 == 0x20 */
+#define SPECIAL 64 /* 0x */
+
+#define __do_div(n, base) \
+({ \
+ int __res; \
+ \
+ __res = ((uint64_t) n) % (uint32_t) base; \
+ n = ((uint64_t) n) / (uint32_t) base; \
+ __res; \
+})
+
+static char *number(char *str, const char *end, long num, int base, int size,
+ int precision, int type)
+{
+ /* we are called with base 8, 10 or 16, only, thus don't need "G..." */
+ static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
+
+ char tmp[66];
+ char c, sign, locase;
+ int i;
+
+ /*
+ * locase = 0 or 0x20. ORing digits or letters with 'locase'
+ * produces same digits or (maybe lowercased) letters
+ */
+ locase = (type & SMALL);
+ if (type & LEFT)
+ type &= ~ZEROPAD;
+ if (base < 2 || base > 16)
+ return NULL;
+ c = (type & ZEROPAD) ? '0' : ' ';
+ sign = 0;
+ if (type & SIGN) {
+ if (num < 0) {
+ sign = '-';
+ num = -num;
+ size--;
+ } else if (type & PLUS) {
+ sign = '+';
+ size--;
+ } else if (type & SPACE) {
+ sign = ' ';
+ size--;
+ }
+ }
+ if (type & SPECIAL) {
+ if (base == 16)
+ size -= 2;
+ else if (base == 8)
+ size--;
+ }
+ i = 0;
+ if (num == 0)
+ tmp[i++] = '0';
+ else
+ while (num != 0)
+ tmp[i++] = (digits[__do_div(num, base)] | locase);
+ if (i > precision)
+ precision = i;
+ size -= precision;
+ if (!(type & (ZEROPAD + LEFT)))
+ while (size-- > 0)
+ APPEND_BUFFER_SAFE(str, end, ' ');
+ if (sign)
+ APPEND_BUFFER_SAFE(str, end, sign);
+ if (type & SPECIAL) {
+ if (base == 8)
+ APPEND_BUFFER_SAFE(str, end, '0');
+ else if (base == 16) {
+ APPEND_BUFFER_SAFE(str, end, '0');
+ APPEND_BUFFER_SAFE(str, end, 'x');
+ }
+ }
+ if (!(type & LEFT))
+ while (size-- > 0)
+ APPEND_BUFFER_SAFE(str, end, c);
+ while (i < precision--)
+ APPEND_BUFFER_SAFE(str, end, '0');
+ while (i-- > 0)
+ APPEND_BUFFER_SAFE(str, end, tmp[i]);
+ while (size-- > 0)
+ APPEND_BUFFER_SAFE(str, end, ' ');
+
+ return str;
+}
+
+int guest_vsnprintf(char *buf, int n, const char *fmt, va_list args)
+{
+ char *str, *end;
+ const char *s;
+ uint64_t num;
+ int i, base;
+ int len;
+
+ int flags; /* flags to number() */
+
+ int field_width; /* width of output field */
+ int precision; /*
+ * min. # of digits for integers; max
+ * number of chars for from string
+ */
+ int qualifier; /* 'h', 'l', or 'L' for integer fields */
+
+ end = buf + n;
+ GUEST_ASSERT(buf < end);
+ GUEST_ASSERT(n > 0);
+
+ for (str = buf; *fmt; ++fmt) {
+ if (*fmt != '%') {
+ APPEND_BUFFER_SAFE(str, end, *fmt);
+ continue;
+ }
+
+ /* process flags */
+ flags = 0;
+repeat:
+ ++fmt; /* this also skips first '%' */
+ switch (*fmt) {
+ case '-':
+ flags |= LEFT;
+ goto repeat;
+ case '+':
+ flags |= PLUS;
+ goto repeat;
+ case ' ':
+ flags |= SPACE;
+ goto repeat;
+ case '#':
+ flags |= SPECIAL;
+ goto repeat;
+ case '0':
+ flags |= ZEROPAD;
+ goto repeat;
+ }
+
+ /* get field width */
+ field_width = -1;
+ if (isdigit(*fmt))
+ field_width = skip_atoi(&fmt);
+ else if (*fmt == '*') {
+ ++fmt;
+ /* it's the next argument */
+ field_width = va_arg(args, int);
+ if (field_width < 0) {
+ field_width = -field_width;
+ flags |= LEFT;
+ }
+ }
+
+ /* get the precision */
+ precision = -1;
+ if (*fmt == '.') {
+ ++fmt;
+ if (isdigit(*fmt))
+ precision = skip_atoi(&fmt);
+ else if (*fmt == '*') {
+ ++fmt;
+ /* it's the next argument */
+ precision = va_arg(args, int);
+ }
+ if (precision < 0)
+ precision = 0;
+ }
+
+ /* get the conversion qualifier */
+ qualifier = -1;
+ if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L') {
+ qualifier = *fmt;
+ ++fmt;
+ }
+
+ /* default base */
+ base = 10;
+
+ switch (*fmt) {
+ case 'c':
+ if (!(flags & LEFT))
+ while (--field_width > 0)
+ APPEND_BUFFER_SAFE(str, end, ' ');
+ APPEND_BUFFER_SAFE(str, end,
+ (uint8_t)va_arg(args, int));
+ while (--field_width > 0)
+ APPEND_BUFFER_SAFE(str, end, ' ');
+ continue;
+
+ case 's':
+ s = va_arg(args, char *);
+ len = strnlen(s, precision);
+
+ if (!(flags & LEFT))
+ while (len < field_width--)
+ APPEND_BUFFER_SAFE(str, end, ' ');
+ for (i = 0; i < len; ++i)
+ APPEND_BUFFER_SAFE(str, end, *s++);
+ while (len < field_width--)
+ APPEND_BUFFER_SAFE(str, end, ' ');
+ continue;
+
+ case 'p':
+ if (field_width == -1) {
+ field_width = 2 * sizeof(void *);
+ flags |= SPECIAL | SMALL | ZEROPAD;
+ }
+ str = number(str, end,
+ (uint64_t)va_arg(args, void *), 16,
+ field_width, precision, flags);
+ continue;
+
+ case 'n':
+ if (qualifier == 'l') {
+ long *ip = va_arg(args, long *);
+ *ip = (str - buf);
+ } else {
+ int *ip = va_arg(args, int *);
+ *ip = (str - buf);
+ }
+ continue;
+
+ case '%':
+ APPEND_BUFFER_SAFE(str, end, '%');
+ continue;
+
+ /* integer number formats - set up the flags and "break" */
+ case 'o':
+ base = 8;
+ break;
+
+ case 'x':
+ flags |= SMALL;
+ case 'X':
+ base = 16;
+ break;
+
+ case 'd':
+ case 'i':
+ flags |= SIGN;
+ case 'u':
+ break;
+
+ default:
+ APPEND_BUFFER_SAFE(str, end, '%');
+ if (*fmt)
+ APPEND_BUFFER_SAFE(str, end, *fmt);
+ else
+ --fmt;
+ continue;
+ }
+ if (qualifier == 'l')
+ num = va_arg(args, uint64_t);
+ else if (qualifier == 'h') {
+ num = (uint16_t)va_arg(args, int);
+ if (flags & SIGN)
+ num = (int16_t)num;
+ } else if (flags & SIGN)
+ num = va_arg(args, int);
+ else
+ num = va_arg(args, uint32_t);
+ str = number(str, end, num, base, field_width, precision, flags);
+ }
+
+ GUEST_ASSERT(str < end);
+ *str = '\0';
+ return str - buf;
+}
+
+int guest_snprintf(char *buf, int n, const char *fmt, ...)
+{
+ va_list va;
+ int len;
+
+ va_start(va, fmt);
+ len = guest_vsnprintf(buf, n, fmt, va);
+ va_end(va);
+
+ return len;
+}
--
2.41.0.487.g6d72f3e995-goog
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