libbb: create and use mmap() helpers

function                                             old     new   delta
mmap_anon                                              -      22     +22
mmap_read                                              -      21     +21
xmmap_anon                                             -      16     +16
rpm_gettags                                          465     447     -18
bb_full_fd_action                                    498     480     -18
uevent_main                                          337     310     -27
------------------------------------------------------------------------------
(add/remove: 3/0 grow/shrink: 0/3 up/down: 59/-63)             Total: -4 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2020-12-14 18:25:28 +01:00
parent db793480cb
commit fd3c512f88
6 changed files with 28 additions and 12 deletions

View File

@ -145,7 +145,7 @@ static int rpm_gettags(const char *filename)
/* remember size for munmap */ /* remember size for munmap */
G.mapsize = storepos; G.mapsize = storepos;
/* some NOMMU systems prefer MAP_PRIVATE over MAP_SHARED */ /* some NOMMU systems prefer MAP_PRIVATE over MAP_SHARED */
G.map = mmap(0, storepos, PROT_READ, MAP_PRIVATE, fd, 0); G.map = mmap_read(fd, storepos);
if (G.map == MAP_FAILED) if (G.map == MAP_FAILED)
bb_perror_msg_and_die("mmap '%s'", filename); bb_perror_msg_and_die("mmap '%s'", filename);

View File

@ -387,6 +387,9 @@ void* xrealloc_vector_helper(void *vector, unsigned sizeof_and_shift, int idx) F
char *xstrdup(const char *s) FAST_FUNC RETURNS_MALLOC; char *xstrdup(const char *s) FAST_FUNC RETURNS_MALLOC;
char *xstrndup(const char *s, int n) FAST_FUNC RETURNS_MALLOC; char *xstrndup(const char *s, int n) FAST_FUNC RETURNS_MALLOC;
void *xmemdup(const void *s, int n) FAST_FUNC RETURNS_MALLOC; void *xmemdup(const void *s, int n) FAST_FUNC RETURNS_MALLOC;
void *mmap_read(int fd, size_t size) FAST_FUNC;
void *mmap_anon(size_t size) FAST_FUNC;
void *xmmap_anon(size_t size) FAST_FUNC;
//TODO: supply a pointer to char[11] buffer (avoid statics)? //TODO: supply a pointer to char[11] buffer (avoid statics)?

View File

@ -75,10 +75,7 @@ static off_t bb_full_fd_action(int src_fd, int dst_fd, off_t size)
goto use_small_buf; goto use_small_buf;
/* We want page-aligned buffer, just in case kernel is clever /* We want page-aligned buffer, just in case kernel is clever
* and can do page-aligned io more efficiently */ * and can do page-aligned io more efficiently */
buffer = mmap(NULL, CONFIG_FEATURE_COPYBUF_KB * 1024, buffer = mmap_anon(CONFIG_FEATURE_COPYBUF_KB * 1024);
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON,
/* ignored: */ -1, 0);
buffer_size = CONFIG_FEATURE_COPYBUF_KB * 1024; buffer_size = CONFIG_FEATURE_COPYBUF_KB * 1024;
if (buffer == MAP_FAILED) { if (buffer == MAP_FAILED) {
use_small_buf: use_small_buf:

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@ -111,6 +111,27 @@ void* FAST_FUNC xmemdup(const void *s, int n)
return memcpy(xmalloc(n), s, n); return memcpy(xmalloc(n), s, n);
} }
void* FAST_FUNC mmap_read(int fd, size_t size)
{
return mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
}
void* FAST_FUNC mmap_anon(size_t size)
{
return mmap(NULL, size,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANONYMOUS,
/* ignored: */ -1, 0);
}
void* FAST_FUNC xmmap_anon(size_t size)
{
void *p = mmap_anon(size);
if (p == MAP_FAILED)
bb_die_memory_exhausted();
return p;
}
// Die if we can't open a file and return a FILE* to it. // Die if we can't open a file and return a FILE* to it.
// Notice we haven't got xfread(), This is for use with fscanf() and friends. // Notice we haven't got xfread(), This is for use with fscanf() and friends.
FILE* FAST_FUNC xfopen(const char *path, const char *mode) FILE* FAST_FUNC xfopen(const char *path, const char *mode)

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@ -169,7 +169,7 @@ void* FAST_FUNC try_to_mmap_module(const char *filename, size_t *image_size_p)
/* st.st_size is off_t, we can't just pass it to mmap */ /* st.st_size is off_t, we can't just pass it to mmap */
if (st.st_size <= *image_size_p) { if (st.st_size <= *image_size_p) {
size_t image_size = st.st_size; size_t image_size = st.st_size;
image = mmap(NULL, image_size, PROT_READ, MAP_PRIVATE, fd, 0); image = mmap_read(fd, image_size);
if (image == MAP_FAILED) { if (image == MAP_FAILED) {
image = NULL; image = NULL;
} else if (*(uint32_t*)image != SWAP_BE32(0x7f454C46)) { } else if (*(uint32_t*)image != SWAP_BE32(0x7f454C46)) {

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@ -74,12 +74,7 @@ int uevent_main(int argc UNUSED_PARAM, char **argv)
// for a new uevent notification to come in. // for a new uevent notification to come in.
// We use a fresh mmap so that buffer is not allocated // We use a fresh mmap so that buffer is not allocated
// until kernel actually starts filling it. // until kernel actually starts filling it.
netbuf = mmap(NULL, USER_RCVBUF, netbuf = xmmap_anon(USER_RCVBUF);
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON,
/* ignored: */ -1, 0);
if (netbuf == MAP_FAILED)
bb_simple_perror_msg_and_die("mmap");
// Here we block, possibly for a very long time // Here we block, possibly for a very long time
len = safe_read(fd, netbuf, USER_RCVBUF - 1); len = safe_read(fd, netbuf, USER_RCVBUF - 1);