syscall: fix fstatfs(2) use for x32

x32 syscalls all seem to have 0x40000000 added to them, so the
low x86-64 number seems obviously wrong.  Tested on an x32 btrfs
chroot where I also realized the statfs.f_type field is 8 bytes
since x32 kernels are 64-bit.

diff --git a/lib/PublicInbox/Syscall.pm b/lib/PublicInbox/Syscall.pm
index 426bdf0be4ce1d31741d5b30c5655584c9adaf99..a7fa37363ec5e30650f2258de2f3ac1c3b012cac 100644 (file)
--- a/lib/PublicInbox/Syscall.pm
+++ b/lib/PublicInbox/Syscall.pm
@@ -24,6 +24,7 @@ use Socket qw(SOL_SOCKET SCM_RIGHTS);
 use Config;
 our %SIGNUM = (WINCH => 28); # most Linux, {Free,Net,Open}BSD, *Darwin
 our ($INOTIFY, %CONST);
+my $FSWORD_T = 'l!'; # for unpack, tested on x86 and x86-64, `q' on x32
 use List::Util qw(sum);
 
 # $VERSION = '0.25'; # Sys::Syscall version
@@ -125,7 +126,7 @@ if ($^O eq "linux") {
                $SYS_epoll_ctl = 1073742057;
                $SYS_epoll_pwait //= 0x40000000 + 281;
                $SYS_renameat2 //= 0x40000000 + 316;
-               $SYS_fstatfs = 138;
+               $SYS_fstatfs = 0x40000000 + 138;
                $SYS_sendmsg = 0x40000206;
                $SYS_recvmsg = 0x40000207;
                $SYS_writev = 0x40000204;
@@ -439,7 +440,7 @@ sub nodatacow_fh ($) {
        my $buf = "\0" x 120;
        syscall($SYS_fstatfs // return, fileno($fh), $buf) == 0 or
                return warn("fstatfs: $!\n");
-       my $f_type = unpack('l!', $buf); # statfs.f_type is a signed word
+       my $f_type = unpack($FSWORD_T, $buf);
        return if $f_type != 0x9123683E; # BTRFS_SUPER_MAGIC
 
        $FS_IOC_GETFLAGS //