From: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Tue, 1 Mar 2022 09:44:14 +0000 (+0000)
Subject: cheri: rseq: remove const to avoid readonly permission
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=1865211ef5d027f10033397b8c5d46052f069cec;p=thirdparty%2Fglibc.git

cheri: rseq: remove const to avoid readonly permission

Using const on the definition does not work for a pure capability ABI:
the capability permissions when accessing the object will be read only.

Use a hack to hide the public declaration in the TU where the const
objects are initialized. (This should work on non-capability targets
too, but to err on the safe side only enable the hack on capability
targets.)
---

diff --git a/sysdeps/nptl/dl-tls_init_tp.c b/sysdeps/nptl/dl-tls_init_tp.c
index 53fba774a55..e4d7bb71ad5 100644
--- a/sysdeps/nptl/dl-tls_init_tp.c
+++ b/sysdeps/nptl/dl-tls_init_tp.c
@@ -16,6 +16,15 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+#ifdef __CHERI_PURE_CAPABILITY__
+/* This hack ensures that the later indirectly included public const
+   declaration does not conflict with the non-const definition here.  */
+# define __rseq_size __rseq_size_public_const
+# define __rseq_offset __rseq_offset_public_const
+# include <sys/rseq.h>
+# undef __rseq_size
+# undef __rseq_offset
+#endif
 #include <kernel-features.h>
 #include <ldsodefs.h>
 #include <list.h>
@@ -45,8 +54,13 @@ rtld_mutex_dummy (pthread_mutex_t *lock)
 #endif
 
 const unsigned int __rseq_flags;
+#ifdef __CHERI_PURE_CAPABILITY__
+unsigned int __rseq_size attribute_relro;
+ptrdiff_t __rseq_offset attribute_relro;
+#else
 const unsigned int __rseq_size attribute_relro;
 const ptrdiff_t __rseq_offset attribute_relro;
+#endif
 
 void
 __tls_pre_init_tp (void)