[PATCH 2/3] arm: Add compile-time asserts for siginfo_t offsets

Marco Elver
2021-04-29T19:18:57Z

To help catch ABI breaks at compile-time, add compile-time assertions to
verify the siginfo_t layout.

This could have caught that we cannot portably add 64-bit integers to
siginfo_t on 32-bit architectures like Arm before reaching -next:
https://lkml.kernel.org/r/20210422191823.79012-1-elver@google.com

Signed-off-by: Marco Elver <elver@google.com>
---
arch/arm/kernel/signal.c | 36 ++++++++++++++++++++++++++++++++++++
1 file changed, 36 insertions(+)

diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index a3a38d0a4c85..2dac5d2c5cf6 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -725,3 +725,39 @@ asmlinkage void do_rseq_syscall(struct pt_regs *regs)
rseq_syscall(regs);
}
#endif
+
+/*
+ * Compile-time assertions for siginfo_t offsets. Check NSIG* as well, as
+ * changes likely come with new fields that should be added below.
+ */
+static_assert(NSIGILL == 11);
+static_assert(NSIGFPE == 15);
+static_assert(NSIGSEGV == 9);
+static_assert(NSIGBUS == 5);
+static_assert(NSIGTRAP == 6);
+static_assert(NSIGCHLD == 6);
+static_assert(NSIGSYS == 2);
+static_assert(offsetof(siginfo_t, si_signo) == 0x00);
+static_assert(offsetof(siginfo_t, si_errno) == 0x04);
+static_assert(offsetof(siginfo_t, si_code) == 0x08);
+static_assert(offsetof(siginfo_t, si_pid) == 0x0c);
+static_assert(offsetof(siginfo_t, si_uid) == 0x10);
+static_assert(offsetof(siginfo_t, si_tid) == 0x0c);
+static_assert(offsetof(siginfo_t, si_overrun) == 0x10);
+static_assert(offsetof(siginfo_t, si_status) == 0x14);
+static_assert(offsetof(siginfo_t, si_utime) == 0x18);
+static_assert(offsetof(siginfo_t, si_stime) == 0x1c);
+static_assert(offsetof(siginfo_t, si_value) == 0x14);
+static_assert(offsetof(siginfo_t, si_int) == 0x14);
+static_assert(offsetof(siginfo_t, si_ptr) == 0x14);
+static_assert(offsetof(siginfo_t, si_addr) == 0x0c);
+static_assert(offsetof(siginfo_t, si_addr_lsb) == 0x10);
+static_assert(offsetof(siginfo_t, si_lower) == 0x14);
+static_assert(offsetof(siginfo_t, si_upper) == 0x18);
+static_assert(offsetof(siginfo_t, si_pkey) == 0x14);
+static_assert(offsetof(siginfo_t, si_perf) == 0x10);
+static_assert(offsetof(siginfo_t, si_band) == 0x0c);
+static_assert(offsetof(siginfo_t, si_fd) == 0x10);
+static_assert(offsetof(siginfo_t, si_call_addr) == 0x0c);
+static_assert(offsetof(siginfo_t, si_syscall) == 0x10);
+static_assert(offsetof(siginfo_t, si_arch) == 0x14);
--
2.31.1.527.g47e6f16901-goog