coja/lbmk
1
0
Fork 0
mirror of https://codeberg.org/libreboot/lbmk.git synced 2026-07-12 14:32:42 +02:00
Code Issues Packages Projects Releases Wiki Activity

libreboot-utils: optimised string functions

Browse Source 
operate per word, not per byte

this is also done on sdup, which uses a slightly
inefficient method: the new string allocation is
that of the maximum size, rather than what we
need. for example, if you wanted a 20 character
string (21 including null), you would still allocate
4096 bytes if that was the maximum length.

it's a bit naughty, and i have half a mind to
keep sdup on the old implementation, but i'll leave
it be for now.

Signed-off-by: Leah Rowe <leah@libreboot.org>
This commit is contained in:
Leah Rowe
2026-03-30 00:35:56 +01:00
parent 7fb0b2f692
commit 9d4302deb2
2 changed files with 191 additions and 50 deletions
Download Patch File Download Diff File Expand all files Collapse all files
util/libreboot-utils/include/common.h
+4
View File
@@ -372,6 +372,8 @@ void write_mac_part(size_t partnum);
/* string functions
*/
size_t page_remain(const void *p);
long pagesize(void);
int xunveilx(const char *path, const char *permissions);
int xpledgex(const char *promises, const char *execpromises);
char *smalloc(char **buf, size_t size);
@@ -381,6 +383,8 @@ int slen(const char *scmp, size_t maxlen,
int vcmp(const void *s1, const void *s2, size_t n);
int scmp(const char *a, const char *b,
size_t maxlen, int *rval);
int ccmp(const char *a, const char *b, size_t i,
int *rval);
int sdup(const char *s,
size_t n, char **dest);
int scatn(ssize_t sc, const char **sv,
util/libreboot-utils/lib/string.c
+187 -50
View File
@@ -19,6 +19,39 @@
#include "../include/common.h"
/* for null detection inside
* word-optimised string functions
*/
#define ff ((size_t)-1 / 0xFF)
#define high ((ff) * 0x80)
#define zeroes(x) (((x) - (ff)) & ~(x) & (high))
size_t
page_remain(const void *p)
{
static size_t pagesz = 0;
if (!pagesz)
pagesz = pagesize(),
pagesz -= ((uintptr_t)p & (pagesz - 1));
return pagesz;
}
long
pagesize(void)
{
static long rval = 0;
static int set = 0;
if (!set) {
if ((rval = sysconf(_SC_PAGESIZE)) < 0)
err_exit(errno, "could not determine page size");
set = 1;
}
return rval;
}
void
free_and_set_null(char **buf)
{
@@ -78,16 +111,17 @@ vmalloc(void **buf, size_t size)
return *buf = rval;
}
/* strict strcmp */
/* strict word-based strcmp */
int
scmp(const char *a,
const char *b,
size_t maxlen,
int *rval)
{
size_t ch;
unsigned char ac;
unsigned char bc;
size_t i = 0;
size_t j;
size_t wa;
size_t wb;
if (a == NULL ||
b == NULL ||
@@ -96,22 +130,36 @@ scmp(const char *a,
goto err;
}
for (ch = 0; ch < maxlen; ch++) {
for ( ; ((uintptr_t)(a + i) % sizeof(size_t)) != 0; i++) {
ac = (unsigned char)a[ch];
bc = (unsigned char)b[ch];
if (ac != bc) {
*rval = ac - bc;
if (i >= maxlen)
goto err;
else if (!ccmp(a, b, i, rval))
return 0;
}
if (ac == '\0') {
*rval = 0;
return 0;
}
}
for ( ; i + sizeof(size_t) <= maxlen;
i += sizeof(size_t)) {
memcpy(&wa, a + i, sizeof(size_t));
memcpy(&wb, b + i, sizeof(size_t));
if (wa != wb)
for (j = 0; j < sizeof(size_t); j++)
if (!ccmp(a, b, i + j, rval))
return 0;
if (!zeroes(wa))
continue;
*rval = 0;
return 0;
}
for ( ; i < maxlen; i++)
if (!ccmp(a, b, i, rval))
return 0;
err:
errno = EFAULT;
if (rval != NULL)
@@ -119,13 +167,39 @@ err:
return -1;
}
/* strict strlen */
int ccmp(const char *a, const char *b,
size_t i, int *rval)
{
unsigned char ac;
unsigned char bc;
if (if_err(a == NULL || b == NULL, EFAULT) ||
rval == NULL)
return -1;
ac = (unsigned char)a[i];
bc = (unsigned char)b[i];
if (ac != bc) {
*rval = ac - bc;
return 0;
} else if (ac == '\0') {
*rval = 0;
return 0;
}
return 1;
}
/* strict word-based strlen */
int
slen(const char *s,
size_t maxlen,
size_t *rval)
{
size_t ch;
size_t i = 0;
size_t w;
size_t j;
if (s == NULL ||
rval == NULL) {
@@ -133,44 +207,109 @@ slen(const char *s,
goto err;
}
for (ch = 0;
ch < maxlen && s[ch] != '\0';
ch++);
for ( ; ((uintptr_t)(s + i) % sizeof(size_t)) != 0; i++) {
if (ch == maxlen) {
/* unterminated */
errno = EFAULT;
goto err;
if (i >= maxlen)
goto err;
if (s[i] == '\0') {
*rval = i;
return 0;
}
}
for ( ; i + sizeof(size_t) <= maxlen;
i += sizeof(size_t)) {
memcpy(&w, s + i, sizeof(size_t));
if (!zeroes(w))
continue;
for (j = 0; j < sizeof(size_t); j++) {
if (s[i + j] == '\0') {
*rval = i + j;
return 0;
}
}
}
for ( ; i < maxlen; i++) {
if (s[i] == '\0') {
*rval = i;
return 0;
}
}
*rval = ch;
return 0;
err:
errno = EFAULT;
if (rval != NULL)
*rval = 0;
return -1;
}
/* strict strdup */
/* strict word-based strdup */
int
sdup(const char *s,
size_t n, char **dest)
size_t max, char **dest)
{
size_t size;
char *rval = NULL;
size_t j;
size_t w;
size_t i = 0;
char *out = NULL;
if (dest == NULL ||
slen(s, n, &size) < 0) {
if (dest != NULL)
*dest = NULL;
return -1;
if (dest == NULL || *dest != NULL || s == NULL)
goto err;
out = smalloc(dest, max);
for ( ; ((uintptr_t)(s + i) % sizeof(size_t)) != 0; i++) {
if (i >= max)
goto err;
out[i] = s[i];
if (s[i] == '\0') {
*dest = out;
return 0;
}
}
memcpy(smalloc(&rval, size + 1), s, size);
*(rval + size) = '\0';
for ( ; i + sizeof(size_t) <= max; i += sizeof(size_t)) {
*dest = rval;
return 0;
if (page_remain(s + i) < sizeof(size_t))
break;
memcpy(&w, s + i, sizeof(size_t));
if (!zeroes(w)) {
memcpy(out + i, &w, sizeof(size_t));
continue;
}
for (j = 0; j < sizeof(size_t); j++) {
out[i + j] = s[i + j];
if (s[i + j] == '\0') {
*dest = out;
return 0;
}
}
}
for ( ; i < max; i++) {
out[i] = s[i];
if (s[i] == '\0') {
*dest = out;
return 0;
}
}
err:
free_and_set_null(&out);
if (dest != NULL)
*dest = NULL;
errno = EFAULT;
return -1;
}
/* concatenate N number of strings */
@@ -279,15 +418,10 @@ dcat(const char *s, size_t n,
return 0;
err:
if (rval1 != NULL)
free(rval1);
if (rval2 != NULL)
free(rval2);
*dest1 = *dest2 = NULL;
if (dest1 != NULL)
*dest1 = NULL;
if (dest2 != NULL)
*dest2 = NULL;
free_and_set_null(&rval1);
free_and_set_null(&rval2);
return -1;
}
@@ -303,11 +437,14 @@ vcmp(const void *s1, const void *s2, size_t n)
size_t a;
size_t b;
const unsigned char *x;
const unsigned char *y;
if (if_err(s1 == NULL || s2 == NULL, EFAULT))
err_exit(EFAULT, "vcmp: null input");
const unsigned char *x = s1;
const unsigned char *y = s2;
x = s1;
y = s2;
for ( ; i + sizeof(size_t) <= n; i += sizeof(size_t)) {