EliasFleckenstein03
/
plan9front
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

pc64: handle negative file offsets when accessing kernel memory with devproc 

file offset is 64 bit signed integer, negative offsets
are invalid and rejected by the kernel. to still access
kernel memory on amd64, we unconditionally clear the sign
bit of the 64 bit offset in libmach and devproc sign
extends the offset back to a 64 bit address.
front
cinap_lenrek 2014-02-08 03:50:41 +01:00
parent 43212f6432
commit 6b146c70c2
2 changed files with 15 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
sys/src/9/port/devproc.c
View File

@ -708,6 +708,10 @@ procread(Chan *c, void *va, long n, vlong off)
Waitq *wq;
a = va;
/* sign extend 63 bit to 64 bit */
off <<= 1;
off >>= 1;
offset = off;
if(c->qid.type & QTDIR)

12
sys/src/libmach/access.c
View File

@ -263,7 +263,17 @@ reloc(Map *map, uvlong addr, vlong *offp)
for (i = 0; i < map->nsegs; i++) {
if (map->seg[i].inuse)
if (map->seg[i].b <= addr && addr < map->seg[i].e) {
*offp = addr + map->seg[i].f - map->seg[i].b;
addr += map->seg[i].f - map->seg[i].b;
/*
* avoid negative file offsets for kernel
* addresses by clearing the sign bit.
* devproc sign extends back to 64 bit.
*/
addr <<= 1;
addr >>= 1;
*offp = addr;
return &map->seg[i];
}
}