From f55e3cae0843417e4a981399db0bdf65ecaa6500 Mon Sep 17 00:00:00 2001
From: David van Moolenbroek <david@minix3.org>
Date: Fri, 4 Sep 2015 03:28:24 +0200
Subject: [PATCH] libmagic: fix ASR padding for memory mapping

The code could not decide whether to apply the padding to the start
or the end of the region, resulting in strange behavior because part
of the returned range might not have the right properties.  With this
patch, padding is now consistently applied at the end of the region,
since virtual mmap addresses are allocated from high to low.

Also fix a few small related bugs in error handling code.

Change-Id: I327814bb3921d7982ffc1296a5bf365d9c79c1d9
---
 minix/llvm/static/magic/magic_mem.c | 10 +++++-----
 minix/llvm/static/magic/magic_st.c  |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/minix/llvm/static/magic/magic_mem.c b/minix/llvm/static/magic/magic_mem.c
index c9a7ac910..b25e1c8c1 100644
--- a/minix/llvm/static/magic/magic_mem.c
+++ b/minix/llvm/static/magic/magic_mem.c
@@ -695,7 +695,7 @@ PRIVATE int magic_free_dsentry(struct _magic_dsentry *dsentry)
             if (!MAGIC_STATE_FLAG(sentry, MAGIC_STATE_DETACHED)) {
                 size_t padding_size = (size_t) dsentry->ext;
                 MAGIC_MEM_DEBUG_FREE(ptr);
-                ret = munmap(((char *)aligned_ptr) - padding_size, page_size + size + padding_size);
+                ret = munmap((char *)aligned_ptr, page_size + size + padding_size);
             }
             else {
 #ifndef __MINIX
@@ -1708,7 +1708,7 @@ PUBLIC void *magic_mmap_positioned(__MA_ARGS__ void *start, size_t length, int p
                 new_start = ((char *)ptr) + page_size;
                 new_ptr = mmap(new_start, length, prot, flags | MAP_FIXED, fd, offset);
                 if (new_ptr == MAP_FAILED) {
-                    munmap(ptr, page_size + alloc_length);
+                    munmap(ptr, page_size + alloc_length + padding_size);
                     ptr = MAP_FAILED;
                 }
             }
@@ -1716,7 +1716,7 @@ PUBLIC void *magic_mmap_positioned(__MA_ARGS__ void *start, size_t length, int p
         aligned_ptr = ptr;
         MAGIC_MEM_PRINTF("magic_mmap: ptr = mmap(start, length, prot, flags, fd, offset) <-> 0x%08x = mmap(0x%08x, %d, 0x%08x, 0x%08x, %d, %d)\n", (unsigned) aligned_ptr, aligned_start, page_size + length, prot, flags, fd, offset);
         if (ptr != MAP_FAILED) {
-            ptr = ((char *)ptr) + padding_size + page_size - MAGIC_SIZE_TO_REAL(0);
+            ptr = ((char *)ptr) + page_size - MAGIC_SIZE_TO_REAL(0);
         }
         else {
             ptr = NULL;
@@ -1725,14 +1725,14 @@ PUBLIC void *magic_mmap_positioned(__MA_ARGS__ void *start, size_t length, int p
             dsentry_flags |= MAGIC_STATE_SHM;
         data_ptr = magic_alloc(__MA_VALUES__ ptr, alloc_length, dsentry_flags);
         if (data_ptr == MAGIC_MEM_FAILED) {
-            munmap(aligned_ptr, page_size + length);
+            munmap(aligned_ptr, page_size + alloc_length + padding_size);
             data_ptr = NULL;
-            errno = ENOMEM;
         }
         if (!data_ptr) {
             errno = ENOMEM;
             data_ptr = MAP_FAILED;
         } else {
+            assert(data_ptr == (char *)aligned_ptr + page_size);
             MAGIC_PTR_TO_DSENTRY(MAGIC_PTR_FROM_DATA(data_ptr))->alloc_mmap_flags = flags;
             MAGIC_PTR_TO_DSENTRY(MAGIC_PTR_FROM_DATA(data_ptr))->alloc_mmap_prot = prot;
             MAGIC_PTR_TO_DSENTRY(MAGIC_PTR_FROM_DATA(data_ptr))->ext = (void *) padding_size;
diff --git a/minix/llvm/static/magic/magic_st.c b/minix/llvm/static/magic/magic_st.c
index 82ca42492..419caecf3 100644
--- a/minix/llvm/static/magic/magic_st.c
+++ b/minix/llvm/static/magic/magic_st.c
@@ -3374,7 +3374,7 @@ PRIVATE int allocate_pair_metadata_dsentries(st_init_info_t *info,
              * in order to free the preceding page, containing the dsentry struct, too.
              */
             MAGIC_MEM_WRAPPER_BLOCK(
-                res = munmap((char *)sentry->address - magic_get_sys_pagesize() - padding, size + magic_get_sys_pagesize() + padding);
+                res = munmap((char *)sentry->address - magic_get_sys_pagesize(), size + magic_get_sys_pagesize() + padding);
             );
             if (res != 0) {
                 printf("ERROR, munmap returned NULL.\n");