On Aarch64, Linux is using Pointer Authentication Code (PAC) for pointer
authentication.[1] The struct "user_pac_mask" has been part of the Linux
kernel since version 5.0 as part of this feature. However, older kernels
do not define it.
Therefore, we want to check if the definition is present in the kernel
headers and provide one if it isn't. This ensures two things:
* elfutils will continue to compile against kernel headers from 4.x
* binaries built against older kernel headers will still be fully
functional if used on a newer system
For reference, the build error that is being avoided looks like this:
[...]
CC aarch64_initreg.o
aarch64_initreg.c: In function 'aarch64_set_initial_registers_tid':
aarch64_initreg.c:61:24: error: storage size of 'pac_mask' isn't known
struct user_pac_mask pac_mask;
^~~~~~~~
aarch64_initreg.c:61:24: warning: unused variable 'pac_mask' [-Wunused-variable]
make[4]: *** [Makefile:831: aarch64_initreg.o] Error 1
make[3]: *** [Makefile:547: all-recursive] Error 1
make[2]: *** [Makefile:463: all] Error 2
[1] https://docs.kernel.org/arch/arm64/pointer-authentication.html
Fixes: 64e3b451ad2c ("aarch64: extend dwfl_thread_state_registers to handle
PAC")
Signed-off-by: Markus Mayer <mma...@broadcom.com>
---
backends/aarch64_initreg.c | 21 +++++++++++++++++++++
configure.ac | 8 ++++++++
2 files changed, 29 insertions(+)
diff --git a/backends/aarch64_initreg.c b/backends/aarch64_initreg.c
index 5ec45ea60d8d..a6badbb45eb0 100644
--- a/backends/aarch64_initreg.c
+++ b/backends/aarch64_initreg.c
@@ -47,6 +47,27 @@
#define BACKEND aarch64_
#include "libebl_CPU.h"
+/*
+ * pointer authentication masks (NT_ARM_PAC_MASK)
+ *
+ * Defined by Linux kernel headers since Linux 5.0. Define it here if kernel
+ * headers are older than that, to ensure this file builds regardless.
+ */
+#if defined(__aarch64__) && defined(__linux__)
+
+#ifndef NT_ARM_PAC_MASK
+#define NT_ARM_PAC_MASK 0x406
+#endif
+
+#ifndef HAVE_USER_PACK_MASK
+struct user_pac_mask {
+ __u64 data_mask;
+ __u64 insn_mask;
+};
+#endif
+
+#endif /* __aarch64__ && __linux__ */
+
bool
aarch64_set_initial_registers_tid (pid_t tid __attribute__ ((unused)),
ebl_tid_registers_t *setfunc __attribute__ ((unused)),
diff --git a/configure.ac b/configure.ac
index e57d39275591..3298f7fc7761 100644
--- a/configure.ac
+++ b/configure.ac
@@ -777,6 +777,14 @@ if test "$sys_user_has_user_regs" = "yes"; then
[Define to 1 if <sys/user.h> defines struct user_regs_struct])
fi
+AC_CHECK_TYPE([struct user_pac_mask],
+ [has_user_pac_mask=yes], [has_user_pac_mask=no],
+ [[#include <asm/ptrace.h>]])
+if test "$has_user_pac_mask" = "yes"; then
+ AC_DEFINE(HAVE_USER_PACK_MASK, 1,
+ [Defined if struct user_pac_mask exists.])
+fi
+
# On a 64-bit host where can can use $CC -m32, we'll run two sets of tests.
utrace_BIARCH
CC_BIARCH="$CC $utrace_biarch"
--
2.48.1
