From: Willy Tarreau <w@1wt.eu>
Date: Tue, 25 Apr 2023 17:01:48 +0000 (+0200)
Subject: DEBUG: crash using an invalid opcode on aarch64 instead of an invalid access
X-Git-Tag: v2.8-dev9~39
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=543e2544cabf9900af92d45658b122bc25011c3d;p=thirdparty%2Fhaproxy.git

DEBUG: crash using an invalid opcode on aarch64 instead of an invalid access

On aarch64 there's also a guaranted invalid instruction, called UDF, and
which even supports an optional 16-bit immediate operand:

   https://developer.arm.com/documentation/ddi0596/2021-12/Base-Instructions/UDF--Permanently-Undefined-?lang=en

It's conveniently encoded as 4 zeroes (when the operand is zero). It's
unclear when support for it was added into GAS, if at all; even a
not-so-old 2.27 doesn't know about it. Let's byte-encode it.

Tested on an A72 and works as expected.
---

diff --git a/include/haproxy/bug.h b/include/haproxy/bug.h
index a07a6c3a35..6ce2066d59 100644
--- a/include/haproxy/bug.h
+++ b/include/haproxy/bug.h
@@ -54,6 +54,13 @@
 		my_unreachable();					\
 	} while (0)
 
+#elif defined(__aarch64__)
+#define ha_crash_now() do {						\
+		/* udf#imm16: 4 bytes (), raises illegal instruction */	\
+		__asm__ volatile(".byte 0x00,0x00,0x00,0x00\n");	\
+		my_unreachable();					\
+	} while (0)
+
 #else // not x86
 
 /* generic implementation, causes a segfault */