e9fddbaad8
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.
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