From: Aaron Lewis <aaronlewis@xxxxxxxxxx> 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@xxxxxxxxxx> Link: https://lore.kernel.org/all/mtdi6smhur5rqffvpu7qux7mptonw223y2653x2nwzvgm72nlo@zyc4w3kwl3rg [sean: add a link to the discussion of other options] Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx> --- 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
