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enable reclaim_gaps for fdpic

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the existing laddr function for fdpic cannot translate ELF virtual
addresses outside of the LOAD segments to runtime addresses because
the fdpic loadmap only covers the logically-mapped part. however the
whole point of reclaim_gaps is to recover the slack space up to the
page boundaries, so it needs to work with such addresses.

add a new laddr_pg function that accepts any address in the page range
for the LOAD segment by expanding the loadmap records out to page
boundaries. only use the new version for reclaim_gaps, so as not to
impact performance of other address lookups.

also, only use laddr_pg for the start address of a gap; the end
address lies one byte beyond the end, potentially in a different page
where it would get mapped differently. instead of mapping end, apply
the length (end-start) to the mapped value of start.
This commit is contained in:
Rich Felker 2018-04-17 15:55:18 -04:00
parent 14032c30e2
commit d610c14855
1 changed files with 18 additions and 2 deletions
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20
ldso/dynlink.c
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@ -158,10 +158,26 @@ static void *laddr(const struct dso *p, size_t v)
for (j=0; v-p->loadmap->segs[j].p_vaddr >= p->loadmap->segs[j].p_memsz; j++);
return (void *)(v - p->loadmap->segs[j].p_vaddr + p->loadmap->segs[j].addr);
}
static void *laddr_pg(const struct dso *p, size_t v)
{
size_t j=0;
size_t pgsz = PAGE_SIZE;
if (!p->loadmap) return p->base + v;
for (j=0; ; j++) {
size_t a = p->loadmap->segs[j].p_vaddr;
size_t b = a + p->loadmap->segs[j].p_memsz;
a &= -pgsz;
b += pgsz-1;
b &= -pgsz;
if (v-a<b-a) break;
}
return (void *)(v - p->loadmap->segs[j].p_vaddr + p->loadmap->segs[j].addr);
}
#define fpaddr(p, v) ((void (*)())&(struct funcdesc){ \
laddr(p, v), (p)->got })
#else
#define laddr(p, v) (void *)((p)->base + (v))
#define laddr_pg(p, v) laddr(p, v)
#define fpaddr(p, v) ((void (*)())laddr(p, v))
#endif
@ -484,7 +500,8 @@ static void reclaim(struct dso *dso, size_t start, size_t end)
if (start >= dso->relro_start && start < dso->relro_end) start = dso->relro_end;
if (end >= dso->relro_start && end < dso->relro_end) end = dso->relro_start;
if (start >= end) return;
__malloc_donate(laddr(dso, start), laddr(dso, end));
char *base = laddr_pg(dso, start);
__malloc_donate(base, base+(end-start));
}
static void reclaim_gaps(struct dso *dso)
@ -492,7 +509,6 @@ static void reclaim_gaps(struct dso *dso)
Phdr *ph = dso->phdr;
size_t phcnt = dso->phnum;
if (DL_FDPIC) return; // FIXME
for (; phcnt--; ph=(void *)((char *)ph+dso->phentsize)) {
if (ph->p_type!=PT_LOAD) continue;
if ((ph->p_flags&(PF_R|PF_W))!=(PF_R|PF_W)) continue;