Fix elf get_load_offset when the binary was linked by lld, which defines read/executable program header offsets not always aligned on a page size.

For example, the same library, linked with ld.bfd will show these PT_LOAD mappings:
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x000000000002b3d0 0x000000000002b3d0  R      0x1000
  LOAD           0x000000000002c000 0x000000000002c000 0x000000000002c000
                 0x000000000001b729 0x000000000001b729  R E    0x1000
  LOAD           0x0000000000048000 0x0000000000048000 0x0000000000048000
                 0x000000000000fb17 0x000000000000fb17  R      0x1000
  LOAD           0x0000000000057fb0 0x0000000000058fb0 0x0000000000058fb0
                 0x00000000000010b0 0x0000000000001508  RW     0x1000

while ld.lld, from the very same .o files, will link it like this:
  LOAD           0x0000000000000000 0x0000000000000000 0x0000000000000000
                 0x000000000003b32c 0x000000000003b32c  R      0x1000
  LOAD           0x000000000003b330 0x000000000003c330 0x000000000003c330
                 0x000000000001b740 0x000000000001b740  R E    0x1000
  LOAD           0x0000000000056a70 0x0000000000058a70 0x0000000000058a70
                 0x0000000000001050 0x0000000000001050  RW     0x1000
  LOAD           0x0000000000057ac0 0x000000000005aac0 0x000000000005aac0
                 0x0000000000000060 0x00000000000004b3  RW     0x1000

Failure to identify the load_offset from iterating the program header lead to later being unable
to find the correct proc_info for a given symbol.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/elfxx.c b/src/elfxx.c
index 2589a3d4..c6baa098 100644
--- a/src/elfxx.c
+++ b/src/elfxx.c
@@ -165,12 +165,17 @@ elf_w (get_load_offset) (struct elf_image *ei, unsigned long segbase,
   Elf_W (Ehdr) *ehdr;
   Elf_W (Phdr) *phdr;
   int i;
+  // mapoff is obtained from mmap informations, so is always aligned on a page size.
+  // PT_LOAD program headers p_offset however is not guaranteed to be aligned on a
+  // page size, ld.lld generate libraries where this is not the case. So we must
+  // make sure we compare both values with the same alignment.
+  unsigned long pagesize_aligment_mask = ~(((unsigned long)getpagesize()) - 1UL);
 
   ehdr = ei->image;
   phdr = (Elf_W (Phdr) *) ((char *) ei->image + ehdr->e_phoff);
 
   for (i = 0; i < ehdr->e_phnum; ++i)
-    if (phdr[i].p_type == PT_LOAD && phdr[i].p_offset == mapoff)
+    if (phdr[i].p_type == PT_LOAD && (phdr[i].p_offset & pagesize_aligment_mask) == mapoff)
       {
         offset = segbase - phdr[i].p_vaddr;
         break;