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memfd_create: don't allocate heap memory

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Rather than calling calloc() to allocate space for a page size array to
pass to getpagesizes(), just follow the getpagesizes() implementation
and allocate MAXPAGESIZES elements on the stack.  This avoids the need
for the allocation.

While this does mean that a new libc is required to take advantage of a
new huge page size, that was already true due to getpagesizes() using a
static buffer of MAXPAGESIZES elements.

Reviewed by:	kevans, imp, emaste
Sponsored by:	DARPA
Differential Revision:	https://reviews.freebsd.org/D42710

(cherry picked from commit c96772227b7dfcaf4eec4d07acb5c916643aca3a)
This commit is contained in:
Brooks Davis 2023-11-27 17:07:06 +00:00
parent 89ebe0ce1f
commit c6e072f15c
1 changed files with 3 additions and 13 deletions
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16
lib/libc/gen/memfd_create.c
View file

@ -35,7 +35,6 @@
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
@ -52,7 +51,8 @@ int
memfd_create(const char *name, unsigned int flags)
{
char memfd_name[NAME_MAX + 1];
size_t namelen, *pgs, pgsize;
size_t pgs[MAXPAGESIZES];
size_t namelen, pgsize;
struct shm_largepage_conf slc;
int error, fd, npgs, oflags, pgidx, saved_errno, shmflags;
@ -92,16 +92,9 @@ memfd_create(const char *name, unsigned int flags)
if (fd == -1 || (flags & MFD_HUGETLB) == 0)
return (fd);
pgs = NULL;
npgs = getpagesizes(NULL, 0);
npgs = getpagesizes(pgs, nitems(pgs));
if (npgs == -1)
goto clean;
pgs = calloc(npgs, sizeof(size_t));
if (pgs == NULL)
goto clean;
error = getpagesizes(pgs, npgs);
if (error == -1)
goto clean;
pgsize = (size_t)1 << ((flags & MFD_HUGE_MASK) >> MFD_HUGE_SHIFT);
for (pgidx = 0; pgidx < npgs; pgidx++) {
if (pgsize == pgs[pgidx])
@ -111,8 +104,6 @@ memfd_create(const char *name, unsigned int flags)
errno = EOPNOTSUPP;
goto clean;
}
free(pgs);
pgs = NULL;
memset(&slc, 0, sizeof(slc));
slc.psind = pgidx;
@ -125,7 +116,6 @@ memfd_create(const char *name, unsigned int flags)
clean:
saved_errno = errno;
close(fd);
free(pgs);
errno = saved_errno;
return (-1);
}