path: root/ldso
diff options
authorRich Felker <>2018-04-17 15:55:18 -0400
committerRich Felker <>2018-04-17 19:23:01 -0400
commitd610c148554766f2a0e48304fe2550b340f84872 (patch)
tree285c50b6cbc152381fe9225b2ea65e3d0e7be508 /ldso
parent14032c30e2d41e5c0dac25d399f7086f74d4e0c8 (diff)
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.
Diffstat (limited to 'ldso')
1 files changed, 18 insertions, 2 deletions
diff --git a/ldso/dynlink.c b/ldso/dynlink.c
index b9ff41bc..63e7b81f 100644
--- 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 })
#define laddr(p, v) (void *)((p)->base + (v))
+#define laddr_pg(p, v) laddr(p, v)
#define fpaddr(p, v) ((void (*)())laddr(p, v))
@@ -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;