[glibc/arm/morello/main] TODO(l_addr): cheri: in static exe initialize l_addr to a zero capability

[glibc/arm/morello/main] TODO(l_addr): cheri: in static exe initialize l_addr to a zero capability

[Szabolcs Nagy]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d257d001c3f16ccc4e4692201d3c03f67a0a9b18

commit d257d001c3f16ccc4e4692201d3c03f67a0a9b18
Author: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date:   Thu Jun 24 13:29:19 2021 +0100

    TODO(l_addr): cheri: in static exe initialize l_addr to a zero capability
    
    The base should be 0, but also a valid capability. Initialize to a zero
    capability instead of relying on AT_BASE.
    
    TODO: this is a hack. we will need stricter bounds and possibly separate
    l_addr and bounds info.

Diff:
---
 elf/dl-support.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/elf/dl-support.c b/elf/dl-support.c
index 4af0b5b2ce..599efb1d08 100644
--- a/elf/dl-support.c
+++ b/elf/dl-support.c
@@ -248,6 +248,14 @@ _dl_aux_init (ElfW(auxv_t) *av)
   GL(dl_sysinfo) = DL_SYSINFO_DEFAULT;
 #endif
 
+#ifdef __CHERI_PURE_CAPABILITY__
+  /* Base is 0 in non-pie static executable, but it needs to be a valid
+     capability. Use the zero capability instead of AT_BASE.  */
+  elfptr_t zerocap;
+  asm volatile ("cvtd %0,xzr" : "=r"(zerocap));
+  _dl_main_map.l_addr = zerocap;
+#endif
+
   _dl_auxv = av;
   dl_parse_auxv_t auxv_values;
   /* Use an explicit initialization loop here because memset may not