ref: e9fddbaad81de8afbffe3f8ff626a18a551619df
parent: ce54a5d6634ab4493504001f9c27568a429ae811
author: cinap_lenrek <cinap_lenrek@felloff.net>
date: Sun Sep 14 12:04:22 EDT 2014
kernel: fix segattach() rounding of va+len (thanks kenji arisawa)
from segattach(2):
Va and len specify the position of the segment in the
process's address space. Va is rounded down to the nearest
page boundary and va+len is rounded up. The system does not
permit segments to overlap. If va is zero, the system will
choose a suitable address.
just rounding up len isnt enougth. we have to round up va+len
instead of just len so that the span [va, va+len) is covered
even if va is not page aligned.
kenjis example:
print("%p\n",ap); // 206cb0
ap = segattach(0, "shared", ap, 1024);
print("%p\n",ap); // 206000
term% cat /proc/612768/segment
Stack defff000 dffff000 1
Text R 1000 6000 1
Data 6000 7000 1
Bss 7000 7000 1
Shared 206000 207000 1
term%
note that 0x206cb0 + 0x400 > 0x20700.
--- a/sys/src/9/port/segment.c
+++ b/sys/src/9/port/segment.c
@@ -610,7 +610,10 @@
}
}
+ /* round up va+len */
+ len += va & (BY2PG-1);
len = PGROUND(len);
+
if(len == 0)
error(Ebadarg);