From 52a747a316042e70a22acb489df9e51bfc6bf2d5 Mon Sep 17 00:00:00 2001 From: Markus Mayer Date: Fri, 21 Feb 2025 11:19:34 -0800 Subject: [PATCH] aarch64: define struct user_pac_mask if needed 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 https://sourceware.org/bugzilla/show_bug.cgi?id=32684 Fixes: 64e3b451ad2c ("aarch64: extend dwfl_thread_state_registers to handle PAC") Signed-off-by: Markus Mayer Signed-off-by: Alex Bennée Upstream: https://sourceware.org/git/?p=elfutils.git;a=commit;h=52a747a316042e70a22acb489df9e51bfc6bf2d5 --- 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 5ec45ea60..a6badbb45 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 e57d39275..3298f7fc7 100644 --- a/configure.ac +++ b/configure.ac @@ -777,6 +777,14 @@ if test "$sys_user_has_user_regs" = "yes"; then [Define to 1 if defines struct user_regs_struct]) fi +AC_CHECK_TYPE([struct user_pac_mask], + [has_user_pac_mask=yes], [has_user_pac_mask=no], + [[#include ]]) +if test "$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" -- 2.43.5