enable reclaim_gaps for fdpic

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.

diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index b9ff41b..63e7b81 100644 (file)
--- a/ldso/dynlink.c
+++ b/ldso/dynlink.c
@@ -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;