aarch64: morello: Add elf_machine_rtld_base_setup

Use a new hook to do the rtld bootstrap map base address and root
capability setup on CHERI.

This will be needed to use separate per module RX and RW root caps.

diff --git a/sysdeps/aarch64/morello/dl-machine.h b/sysdeps/aarch64/morello/dl-machine.h
index 19110d75c5ecb84b1194b7720e1fdcafee235841..ff5169d779de1fbcd6002cbfc8a1989dc92b204e 100644 (file)
--- a/sysdeps/aarch64/morello/dl-machine.h
+++ b/sysdeps/aarch64/morello/dl-machine.h
@@ -101,6 +101,78 @@ elf_machine_runtime_dynamic (void)
   return p;
 }
 
+/* PCC relative access to ehdr before relocations are processed.  */
+static const ElfW(Ehdr) *
+elf_machine_ehdr (void)
+{
+  const void *p;
+  asm (""
+    ".weak __ehdr_start\n"
+    ".hidden __ehdr_start\n"
+    "adrp %0, __ehdr_start\n"
+    "add %0, %0, :lo12:__ehdr_start\n" : "=r"(p));
+  return p;
+}
+
+/* Set up ld.so root capabilities and base address from args.  */
+static void __attribute__ ((unused))
+elf_machine_rtld_base_setup (struct link_map *map, void *args)
+{
+  uintptr_t *sp;
+  long argc;
+  uintptr_t cap_rx, cap_rw, cap_exe_rx, cap_exe_rw;
+  unsigned long ldso_base = 0;
+
+  sp = args;
+  argc = sp[0];
+  /* Skip argv.  */
+  sp += argc + 2;
+  /* Skip environ.  */
+  for (; *sp; sp++);
+  sp++;
+  cap_rx = cap_rw = cap_exe_rx = cap_exe_rw = 0;
+  for (; *sp != AT_NULL; sp += 2)
+    {
+      long t = sp[0];
+      if (t == AT_BASE)
+       ldso_base = sp[1];
+      if (t == AT_CHERI_INTERP_RX_CAP)
+       cap_rx = sp[1];
+      if (t == AT_CHERI_INTERP_RW_CAP)
+       cap_rw = sp[1];
+      if (t == AT_CHERI_EXEC_RX_CAP)
+       cap_exe_rx = sp[1];
+      if (t == AT_CHERI_EXEC_RW_CAP)
+       cap_exe_rw = sp[1];
+    }
+  /* Check if ldso is the executable.  */
+  if (ldso_base == 0)
+    {
+      cap_rx = cap_exe_rx;
+      cap_rw = cap_exe_rw;
+      ldso_base = cap_rx; /* Assume load segments start at vaddr 0.  */
+    }
+  map->l_addr = ldso_base;
+  map->l_map_start = cap_rx;
+  map->l_rw_start = cap_rw;
+
+  /* Set up the RW ranges of ld.so, required for symbolic relocations.  */
+  const ElfW(Ehdr) *ehdr = elf_machine_ehdr ();
+  const ElfW(Phdr) *phdr = (const void *) ehdr + ehdr->e_phoff;
+  if (sizeof *phdr != ehdr->e_phentsize)
+    __builtin_trap ();
+  for (const ElfW(Phdr) *ph = phdr; ph < phdr + ehdr->e_phnum; ph++)
+    if (ph->p_type == PT_LOAD && (ph->p_flags & PF_W))
+      {
+       uintptr_t allocend = map->l_addr + ph->p_vaddr + ph->p_memsz;
+       if (map->l_rw_count >= DL_MAX_RW_COUNT)
+         __builtin_trap ();
+       map->l_rw_range[map->l_rw_count].start = map->l_addr + ph->p_vaddr;
+       map->l_rw_range[map->l_rw_count].end = allocend;
+       map->l_rw_count++;
+      }
+}
+
 /* Load address of the dynamic linker with correct bounds.  */
 static uintptr_t __attribute__ ((unused))
 elf_machine_load_address_from_args (void *arg)