Add NT_ARM_ADDR_MASK

This can be used by debuggers to find which bits in a virtual address
should be masked off to get a canonical address. This is currently used
by the Pointer Authentication Code support to get its mask. It could also
be used if we support Top Byte Ignore for the same purpose.

Reviewed by:	kib
Sponsored by:	The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D34302

sys/arm64/arm64/elf_machdep.c

@@ -59,6 +59,8 @@ __FBSDID("$FreeBSD$");
 u_long __read_frequently elf_hwcap;
 u_long __read_frequently elf_hwcap2;
 
+struct arm64_addr_mask elf64_addr_mask;
+
 static struct sysentvec elf64_freebsd_sysvec = {
 	.sv_size	= SYS_MAXSYSCALL,
 	.sv_table	= sysent,
@@ -119,11 +121,47 @@ static Elf64_Brandinfo freebsd_brand_info = {
 SYSINIT(elf64, SI_SUB_EXEC, SI_ORDER_FIRST,
     (sysinit_cfunc_t)elf64_insert_brand_entry, &freebsd_brand_info);
 
-void
-elf64_dump_thread(struct thread *td __unused, void *dst __unused,
-    size_t *off __unused)
+static bool
+get_arm64_addr_mask(struct regset *rs, struct thread *td, void *buf,
+    size_t *sizep)
 {
+	if (buf != NULL) {
+		KASSERT(*sizep == sizeof(elf64_addr_mask),
+		    ("%s: invalid size", __func__));
+		memcpy(buf, &elf64_addr_mask, sizeof(elf64_addr_mask));
+	}
+	*sizep = sizeof(elf64_addr_mask);
 
+	return (true);
+}
+
+static struct regset regset_arm64_addr_mask = {
+	.note = NT_ARM_ADDR_MASK,
+	.size = sizeof(struct arm64_addr_mask),
+	.get = get_arm64_addr_mask,
+};
+ELF_REGSET(regset_arm64_addr_mask);
+
+void
+elf64_dump_thread(struct thread *td, void *dst, size_t *off)
+{
+	struct arm64_addr_mask addr_mask;
+	size_t len, mask_size;
+
+	len = 0;
+	if (dst != NULL) {
+		mask_size = sizeof(addr_mask);
+		get_arm64_addr_mask(&regset_arm64_addr_mask, td, &addr_mask,
+		    &mask_size);
+
+		len += elf64_populate_note(NT_ARM_ADDR_MASK, &addr_mask, dst,
+		    sizeof(addr_mask), NULL);
+	} else {
+		len += elf64_populate_note(NT_ARM_ADDR_MASK, NULL, NULL,
+		    sizeof(addr_mask), NULL);
+	}
+
+	*off += len;
 }
 
 bool

sys/arm64/arm64/ptrauth.c

@@ -46,6 +46,8 @@ __FBSDID("$FreeBSD$");
 
 #include <machine/armreg.h>
 #include <machine/cpu.h>
+#include <machine/reg.h>
+#include <machine/vmparam.h>
 
 #define	SCTLR_PTRAUTH	(SCTLR_EnIA | SCTLR_EnIB | SCTLR_EnDA | SCTLR_EnDB)
 
@@ -82,8 +84,12 @@ ptrauth_init(void)
 	 * it will also be available on any non-boot CPUs. If this is ever
 	 * not the case we will have to add a quirk.
 	 */
-	if (ID_AA64ISAR1_APA_VAL(isar1) > 0 || ID_AA64ISAR1_API_VAL(isar1) > 0)
+	if (ID_AA64ISAR1_APA_VAL(isar1) > 0 ||
+	    ID_AA64ISAR1_API_VAL(isar1) > 0) {
 		enable_ptrauth = true;
+		elf64_addr_mask.code |= PAC_ADDR_MASK;
+		elf64_addr_mask.data |= PAC_ADDR_MASK;
+	}
 }
 
 /* Copy the keys when forking a new process */

sys/arm64/include/cpu.h

@@ -164,6 +164,9 @@ extern char etext[];
 
 extern uint64_t __cpu_affinity[];
 
+struct arm64_addr_mask;
+extern struct arm64_addr_mask elf64_addr_mask;
+
 void	cpu_halt(void) __dead2;
 void	cpu_reset(void) __dead2;
 void	fork_trampoline(void);

sys/arm64/include/reg.h

@@ -83,6 +83,11 @@ struct dbreg32 {
 	int dummy;
 };
 
+struct arm64_addr_mask {
+	__uint64_t	code;
+	__uint64_t	data;
+};
+
 #define	__HAVE_REG32
 
 #endif /* !_MACHINE_REG_H_ */

sys/arm64/include/vmparam.h

@@ -156,6 +156,9 @@
 #define	VM_MIN_KERNEL_ADDRESS	(0xffff000000000000UL)
 #define	VM_MAX_KERNEL_ADDRESS	(0xffff008000000000UL)
 
+/* The address bits that hold a pointer authentication code */
+#define	PAC_ADDR_MASK		(0xff7f000000000000UL)
+
 /* If true addr is in the kernel address space */
 #define	ADDR_IS_KERNEL(addr)	(((addr) & (1ul << 55)) == (1ul << 55))
 /* If true addr is in its canonical form (i.e. no TBI, PAC, etc.) */

sys/sys/elf_common.h

@@ -825,6 +825,7 @@ typedef struct {
 #define	NT_PPC_VSX	0x102	/* PowerPC VSX registers */
 #define	NT_X86_XSTATE	0x202	/* x86 XSAVE extended state. */
 #define	NT_ARM_VFP	0x400	/* ARM VFP registers */
+#define	NT_ARM_ADDR_MASK	0x406	/* arm64 address mask (e.g. for TBI) */
 
 /* GNU note types. */
 #define	NT_GNU_ABI_TAG		1

tests/sys/kern/ptrace_test.c

@@ -3204,6 +3204,9 @@ ATF_TC_BODY(ptrace__PT_CONTINUE_with_signal_thread_sigmask, tc)
 ATF_TC_WITHOUT_HEAD(ptrace__PT_REGSET);
 ATF_TC_BODY(ptrace__PT_REGSET, tc)
 {
+#if defined(__aarch64__)
+	struct arm64_addr_mask addr_mask;
+#endif
 	struct prstatus prstatus;
 	struct iovec vec;
 	pid_t child, wpid;
@@ -3242,6 +3245,16 @@ ATF_TC_BODY(ptrace__PT_REGSET, tc)
 	ATF_REQUIRE(ptrace(PT_SETREGSET, wpid, (caddr_t)&vec, NT_PRSTATUS) !=
 	    -1);
 
+#if defined(__aarch64__)
+	vec.iov_base = &addr_mask;
+	vec.iov_len = sizeof(addr_mask);
+	ATF_REQUIRE(ptrace(PT_GETREGSET, wpid, (caddr_t)&vec,
+	    NT_ARM_ADDR_MASK) != -1);
+	REQUIRE_EQ(addr_mask.code, addr_mask.data);
+	ATF_REQUIRE(addr_mask.code == 0 ||
+	    addr_mask.code == 0xff7f000000000000UL);
+#endif
+
 	REQUIRE_EQ(ptrace(PT_CONTINUE, child, (caddr_t)1, 0), 0);
 
 	/* The second wait() should report the exit status. */