KVM: selftests: Add guest_snprintf() to KVM selftests
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@google.com> Link: https://lore.kernel.org/all/mtdi6smhur5rqffvpu7qux7mptonw223y2653x2nwzvgm72nlo@zyc4w3kwl3rg [sean: add a link to the discussion of other options] Link: https://lore.kernel.org/r/20230729003643.1053367-6-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Aaron Lewis
Sean Christopherson
parent
a1c1b55e11
commit
e511938249
3 changed files with 311 additions and 0 deletions
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@ -23,6 +23,7 @@ LIBKVM += lib/guest_modes.c
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LIBKVM += lib/io.c
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LIBKVM += lib/kvm_util.c
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LIBKVM += lib/memstress.c
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LIBKVM += lib/guest_sprintf.c
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LIBKVM += lib/rbtree.c
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LIBKVM += lib/sparsebit.c
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LIBKVM += lib/test_util.c
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@ -185,4 +185,7 @@ static inline uint32_t atoi_non_negative(const char *name, const char *num_str)
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return num;
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}
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int guest_vsnprintf(char *buf, int n, const char *fmt, va_list args);
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int guest_snprintf(char *buf, int n, const char *fmt, ...);
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#endif /* SELFTEST_KVM_TEST_UTIL_H */
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307
tools/testing/selftests/kvm/lib/guest_sprintf.c
Normal file
307
tools/testing/selftests/kvm/lib/guest_sprintf.c
Normal file
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@ -0,0 +1,307 @@
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// SPDX-License-Identifier: GPL-2.0-only
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#include "test_util.h"
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#include "kvm_util.h"
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#include "ucall_common.h"
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#define APPEND_BUFFER_SAFE(str, end, v) \
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do { \
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GUEST_ASSERT(str < end); \
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*str++ = (v); \
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} while (0)
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static int isdigit(int ch)
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{
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return (ch >= '0') && (ch <= '9');
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}
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static int skip_atoi(const char **s)
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{
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int i = 0;
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while (isdigit(**s))
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i = i * 10 + *((*s)++) - '0';
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return i;
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}
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#define ZEROPAD 1 /* pad with zero */
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#define SIGN 2 /* unsigned/signed long */
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#define PLUS 4 /* show plus */
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#define SPACE 8 /* space if plus */
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#define LEFT 16 /* left justified */
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#define SMALL 32 /* Must be 32 == 0x20 */
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#define SPECIAL 64 /* 0x */
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#define __do_div(n, base) \
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({ \
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int __res; \
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\
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__res = ((uint64_t) n) % (uint32_t) base; \
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n = ((uint64_t) n) / (uint32_t) base; \
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__res; \
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})
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static char *number(char *str, const char *end, long num, int base, int size,
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int precision, int type)
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{
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/* we are called with base 8, 10 or 16, only, thus don't need "G..." */
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static const char digits[16] = "0123456789ABCDEF"; /* "GHIJKLMNOPQRSTUVWXYZ"; */
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char tmp[66];
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char c, sign, locase;
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int i;
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/*
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* locase = 0 or 0x20. ORing digits or letters with 'locase'
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* produces same digits or (maybe lowercased) letters
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*/
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locase = (type & SMALL);
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if (type & LEFT)
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type &= ~ZEROPAD;
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if (base < 2 || base > 16)
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return NULL;
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c = (type & ZEROPAD) ? '0' : ' ';
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sign = 0;
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if (type & SIGN) {
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if (num < 0) {
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sign = '-';
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num = -num;
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size--;
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} else if (type & PLUS) {
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sign = '+';
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size--;
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} else if (type & SPACE) {
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sign = ' ';
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size--;
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}
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}
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if (type & SPECIAL) {
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if (base == 16)
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size -= 2;
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else if (base == 8)
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size--;
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}
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i = 0;
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if (num == 0)
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tmp[i++] = '0';
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else
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while (num != 0)
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tmp[i++] = (digits[__do_div(num, base)] | locase);
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if (i > precision)
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precision = i;
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size -= precision;
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if (!(type & (ZEROPAD + LEFT)))
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while (size-- > 0)
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APPEND_BUFFER_SAFE(str, end, ' ');
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if (sign)
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APPEND_BUFFER_SAFE(str, end, sign);
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if (type & SPECIAL) {
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if (base == 8)
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APPEND_BUFFER_SAFE(str, end, '0');
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else if (base == 16) {
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APPEND_BUFFER_SAFE(str, end, '0');
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APPEND_BUFFER_SAFE(str, end, 'x');
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}
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}
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if (!(type & LEFT))
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while (size-- > 0)
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APPEND_BUFFER_SAFE(str, end, c);
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while (i < precision--)
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APPEND_BUFFER_SAFE(str, end, '0');
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while (i-- > 0)
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APPEND_BUFFER_SAFE(str, end, tmp[i]);
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while (size-- > 0)
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APPEND_BUFFER_SAFE(str, end, ' ');
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return str;
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}
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int guest_vsnprintf(char *buf, int n, const char *fmt, va_list args)
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{
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char *str, *end;
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const char *s;
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uint64_t num;
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int i, base;
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int len;
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int flags; /* flags to number() */
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int field_width; /* width of output field */
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int precision; /*
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* min. # of digits for integers; max
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* number of chars for from string
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*/
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int qualifier; /* 'h', 'l', or 'L' for integer fields */
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end = buf + n;
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GUEST_ASSERT(buf < end);
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GUEST_ASSERT(n > 0);
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for (str = buf; *fmt; ++fmt) {
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if (*fmt != '%') {
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APPEND_BUFFER_SAFE(str, end, *fmt);
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continue;
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}
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/* process flags */
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flags = 0;
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repeat:
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++fmt; /* this also skips first '%' */
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switch (*fmt) {
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case '-':
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flags |= LEFT;
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goto repeat;
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case '+':
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flags |= PLUS;
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goto repeat;
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case ' ':
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flags |= SPACE;
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goto repeat;
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case '#':
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flags |= SPECIAL;
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goto repeat;
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case '0':
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flags |= ZEROPAD;
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goto repeat;
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}
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/* get field width */
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field_width = -1;
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if (isdigit(*fmt))
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field_width = skip_atoi(&fmt);
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else if (*fmt == '*') {
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++fmt;
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/* it's the next argument */
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field_width = va_arg(args, int);
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if (field_width < 0) {
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field_width = -field_width;
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flags |= LEFT;
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}
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}
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/* get the precision */
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precision = -1;
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if (*fmt == '.') {
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++fmt;
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if (isdigit(*fmt))
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precision = skip_atoi(&fmt);
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else if (*fmt == '*') {
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++fmt;
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/* it's the next argument */
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precision = va_arg(args, int);
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}
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if (precision < 0)
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precision = 0;
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}
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/* get the conversion qualifier */
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qualifier = -1;
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if (*fmt == 'h' || *fmt == 'l' || *fmt == 'L') {
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qualifier = *fmt;
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++fmt;
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}
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/* default base */
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base = 10;
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switch (*fmt) {
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case 'c':
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if (!(flags & LEFT))
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while (--field_width > 0)
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APPEND_BUFFER_SAFE(str, end, ' ');
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APPEND_BUFFER_SAFE(str, end,
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(uint8_t)va_arg(args, int));
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while (--field_width > 0)
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APPEND_BUFFER_SAFE(str, end, ' ');
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continue;
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case 's':
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s = va_arg(args, char *);
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len = strnlen(s, precision);
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if (!(flags & LEFT))
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while (len < field_width--)
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APPEND_BUFFER_SAFE(str, end, ' ');
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for (i = 0; i < len; ++i)
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APPEND_BUFFER_SAFE(str, end, *s++);
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while (len < field_width--)
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APPEND_BUFFER_SAFE(str, end, ' ');
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continue;
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case 'p':
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if (field_width == -1) {
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field_width = 2 * sizeof(void *);
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flags |= SPECIAL | SMALL | ZEROPAD;
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}
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str = number(str, end,
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(uint64_t)va_arg(args, void *), 16,
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field_width, precision, flags);
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continue;
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case 'n':
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if (qualifier == 'l') {
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long *ip = va_arg(args, long *);
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*ip = (str - buf);
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} else {
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int *ip = va_arg(args, int *);
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*ip = (str - buf);
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}
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continue;
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case '%':
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APPEND_BUFFER_SAFE(str, end, '%');
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continue;
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/* integer number formats - set up the flags and "break" */
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case 'o':
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base = 8;
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break;
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case 'x':
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flags |= SMALL;
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case 'X':
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base = 16;
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break;
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case 'd':
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case 'i':
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flags |= SIGN;
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case 'u':
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break;
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default:
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APPEND_BUFFER_SAFE(str, end, '%');
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if (*fmt)
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APPEND_BUFFER_SAFE(str, end, *fmt);
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else
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--fmt;
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continue;
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}
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if (qualifier == 'l')
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num = va_arg(args, uint64_t);
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else if (qualifier == 'h') {
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num = (uint16_t)va_arg(args, int);
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if (flags & SIGN)
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num = (int16_t)num;
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} else if (flags & SIGN)
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num = va_arg(args, int);
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else
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num = va_arg(args, uint32_t);
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str = number(str, end, num, base, field_width, precision, flags);
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}
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GUEST_ASSERT(str < end);
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*str = '\0';
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return str - buf;
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}
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int guest_snprintf(char *buf, int n, const char *fmt, ...)
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{
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va_list va;
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int len;
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va_start(va, fmt);
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len = guest_vsnprintf(buf, n, fmt, va);
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va_end(va);
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return len;
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}
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