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libbb: create and use mmap() helpers

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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
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(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
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7
util-linux/uevent.c
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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.
// We use a fresh mmap so that buffer is not allocated
// until kernel actually starts filling it.
netbuf = mmap(NULL, USER_RCVBUF,
PROT_READ | PROT_WRITE,
MAP_PRIVATE | MAP_ANON,
/* ignored: */ -1, 0);
if (netbuf == MAP_FAILED)
bb_simple_perror_msg_and_die("mmap");
netbuf = xmmap_anon(USER_RCVBUF);
// Here we block, possibly for a very long time
len = safe_read(fd, netbuf, USER_RCVBUF - 1);