(aside: "sig segattach" fails because nroff can elide
all leading space. /n/sources/patch/signit
one could argue for replacing the \*? in
selecting files with \** but no functions
return a **.)
i think segattach is already correct. consider this
#include <u.h>
#include <libc.h>
enum {
Sz = 0x1000,
};
void
main(void)
{
uchar *base, *rb;
base = (uchar*)0x10001001;
rb = segattach(0, "shared", base, Sz - 10);
print("%p\n", rb);
base[0] = 'a';
base[-1] = 'a';
base[Sz - 2] = 'a'; /* note this does not fault, even
though Sz - 10 was used */
>> base[Sz - 1] = 'a';
exits("");
}
% 8.out
10001000 # not 10001001.
81 8.out: checked 8 page table entries
8.out 81: suicide: sys: trap: fault write addr=0x10002000 pc=0x1073
if i were to have used rb and not base, this base[-1] would have
faulted but base[Sz - 1] would have been okay. so i woud think
this is a misunderstanding of how segattach works.
if one wishes to disallow mapping the zero page this
condition should be changed:
if(va != 0 && va >= USTKTOP)
error(Ebadarg);
to
if(va < BY2PG || va >= USTKTOP)
- erik
