fix dynamic loader library mapping for nommu systems

[musl] / src / ldso / dynlink.c

diff --git a/src/ldso/dynlink.c b/src/ldso/dynlink.c
index 642ecc3..5fbe2bb 100644 (file)
--- a/src/ldso/dynlink.c
+++ b/src/ldso/dynlink.c
@@ -482,8 +482,14 @@ static void reclaim_gaps(struct dso *dso)
 
 static void *mmap_fixed(void *p, size_t n, int prot, int flags, int fd, off_t off)
 {
-       char *q = mmap(p, n, prot, flags, fd, off);
-       if (q != MAP_FAILED || errno != EINVAL) return q;
+       static int no_map_fixed;
+       char *q;
+       if (!no_map_fixed) {
+               q = mmap(p, n, prot, flags|MAP_FIXED, fd, off);
+               if (!DL_NOMMU_SUPPORT || q != MAP_FAILED || errno != EINVAL)
+                       return q;
+               no_map_fixed = 1;
+       }
        /* Fallbacks for MAP_FIXED failure on NOMMU kernels. */
        if (flags & MAP_ANONYMOUS) {
                memset(p, 0, n);
@@ -604,6 +610,19 @@ static void *map_library(int fd, struct dso *dso)
                        dso->loadmap->segs[i].p_vaddr = ph->p_vaddr;
                        dso->loadmap->segs[i].p_memsz = ph->p_memsz;
                        i++;
+                       if (prot & PROT_WRITE) {
+                               size_t brk = (ph->p_vaddr & PAGE_SIZE-1)
+                                       + ph->p_filesz;
+                               size_t pgbrk = brk + PAGE_SIZE-1 & -PAGE_SIZE;
+                               size_t pgend = brk + ph->p_memsz - ph->p_filesz
+                                       + PAGE_SIZE-1 & -PAGE_SIZE;
+                               if (pgend > pgbrk && mmap_fixed(map+pgbrk,
+                                       pgend-pgbrk, prot,
+                                       MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS,
+                                       -1, off_start) == MAP_FAILED)
+                                       goto error;
+                               memset(map + brk, 0, pgbrk-brk);
+                       }
                }
                map = (void *)dso->loadmap->segs[0].addr;
                map_len = 0;
@@ -618,7 +637,11 @@ static void *map_library(int fd, struct dso *dso)
         * the length of the file. This is okay because we will not
         * use the invalid part; we just need to reserve the right
         * amount of virtual address space to map over later. */
-       map = mmap((void *)addr_min, map_len, prot, MAP_PRIVATE, fd, off_start);
+       map = DL_NOMMU_SUPPORT
+               ? mmap((void *)addr_min, map_len, PROT_READ|PROT_WRITE|PROT_EXEC,
+                       MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
+               : mmap((void *)addr_min, map_len, prot,
+                       MAP_PRIVATE, fd, off_start);
        if (map==MAP_FAILED) goto error;
        dso->map = map;
        dso->map_len = map_len;
@@ -643,7 +666,8 @@ static void *map_library(int fd, struct dso *dso)
                        dso->phentsize = eh->e_phentsize;
                }
                /* Reuse the existing mapping for the lowest-address LOAD */
-               if ((ph->p_vaddr & -PAGE_SIZE) == addr_min) continue;
+               if ((ph->p_vaddr & -PAGE_SIZE) == addr_min && !DL_NOMMU_SUPPORT)
+                       continue;
                this_min = ph->p_vaddr & -PAGE_SIZE;
                this_max = ph->p_vaddr+ph->p_memsz+PAGE_SIZE-1 & -PAGE_SIZE;
                off_start = ph->p_offset & -PAGE_SIZE;