[PATCH v6 1/6] arm64: kprobe: add checks for ARMv8.3-PAuth combined instructions

[Amit Daniel Kachhap]

Currently the ARMv8.3-PAuth combined branch instructions (braa, retaa
etc.) are not simulated for out-of-line execution with a handler. Hence the
uprobe of such instructions leads to kernel warnings in a loop as they are
not explicitly checked and fall into INSN_GOOD categories. Other combined
instructions like LDRAA and LDRBB can be probed.

The issue of the combined branch instructions is fixed by adding
definitions of all such instructions and rejecting their probes.

Warning log:
 WARNING: CPU: 5 PID: 249 at arch/arm64/kernel/probes/uprobes.c:182 uprobe_single_step_handler+0x34/0x50
 Modules linked in:
 CPU: 5 PID: 249 Comm: func Tainted: G        W         5.8.0-rc4-00005-ge658591d66d1-dirty #160
 Hardware name: Foundation-v8A (DT)
 pstate: 204003c9 (nzCv DAIF +PAN -UAO BTYPE=--)
 pc : uprobe_single_step_handler+0x34/0x50
 lr : single_step_handler+0x70/0xf8
 sp : ffff800012afbe30
 x29: ffff800012afbe30 x28: ffff000879f00ec0
 x27: 0000000000000000 x26: 0000000000000000
 x25: 0000000000000000 x24: 0000000000000000
 x23: 0000000060001000 x22: 00000000cb000022
 x21: ffff800011fc5a68 x20: ffff800012afbec0
 x19: ffff800011fc86c0 x18: 0000000000000000
 x17: 0000000000000000 x16: 0000000000000000
 x15: 0000000000000000 x14: 0000000000000000
 x13: 0000000000000000 x12: 0000000000000000
 x11: 0000000000000000 x10: 0000000000000000
 x9 : ffff800010085d50 x8 : 0000000000000000
 x7 : 0000000000000000 x6 : ffff800011fba9c0
 x5 : ffff800011fba000 x4 : ffff800012283070
 x3 : ffff8000100a78e0 x2 : 00000000004005f0
 x1 : 0000fffffffff008 x0 : ffff800012afbec0
 Call trace:
  uprobe_single_step_handler+0x34/0x50
  single_step_handler+0x70/0xf8
  do_debug_exception+0xb8/0x130
  el0_sync_handler+0x7c/0x188
  el0_sync+0x158/0x180

Fixes: 74afda4016a7 ("arm64: compile the kernel with ptrauth return address signing")
Fixes: 04ca3204fa09 ("arm64: enable pointer authentication")
Signed-off-by: Amit Daniel Kachhap <amit.kachhap at arm.com>
Reviewed-by: Dave Martin <Dave.Martin at arm.com>
---
Changes since v5: 
* Slight change in commit log.
* Added Reviewed-by.

 arch/arm64/include/asm/insn.h          | 12 ++++++++++++
 arch/arm64/kernel/insn.c               | 14 ++++++++++++--
 arch/arm64/kernel/probes/decode-insn.c |  4 +++-
 3 files changed, 27 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h
index 0bc46149e491..324234068fee 100644
--- a/arch/arm64/include/asm/insn.h
+++ b/arch/arm64/include/asm/insn.h
@@ -359,9 +359,21 @@ __AARCH64_INSN_FUNCS(brk,	0xFFE0001F, 0xD4200000)
 __AARCH64_INSN_FUNCS(exception,	0xFF000000, 0xD4000000)
 __AARCH64_INSN_FUNCS(hint,	0xFFFFF01F, 0xD503201F)
 __AARCH64_INSN_FUNCS(br,	0xFFFFFC1F, 0xD61F0000)
+__AARCH64_INSN_FUNCS(braaz,	0xFFFFFC1F, 0xD61F081F)
+__AARCH64_INSN_FUNCS(brabz,	0xFFFFFC1F, 0xD61F0C1F)
+__AARCH64_INSN_FUNCS(braa,	0xFFFFFC00, 0xD71F0800)
+__AARCH64_INSN_FUNCS(brab,	0xFFFFFC00, 0xD71F0C00)
 __AARCH64_INSN_FUNCS(blr,	0xFFFFFC1F, 0xD63F0000)
+__AARCH64_INSN_FUNCS(blraaz,	0xFFFFFC1F, 0xD63F081F)
+__AARCH64_INSN_FUNCS(blrabz,	0xFFFFFC1F, 0xD63F0C1F)
+__AARCH64_INSN_FUNCS(blraa,	0xFFFFFC00, 0xD73F0800)
+__AARCH64_INSN_FUNCS(blrab,	0xFFFFFC00, 0xD73F0C00)
 __AARCH64_INSN_FUNCS(ret,	0xFFFFFC1F, 0xD65F0000)
+__AARCH64_INSN_FUNCS(retaa,	0xFFFFFFFF, 0xD65F0BFF)
+__AARCH64_INSN_FUNCS(retab,	0xFFFFFFFF, 0xD65F0FFF)
 __AARCH64_INSN_FUNCS(eret,	0xFFFFFFFF, 0xD69F03E0)
+__AARCH64_INSN_FUNCS(eretaa,	0xFFFFFFFF, 0xD69F0BFF)
+__AARCH64_INSN_FUNCS(eretab,	0xFFFFFFFF, 0xD69F0FFF)
 __AARCH64_INSN_FUNCS(mrs,	0xFFF00000, 0xD5300000)
 __AARCH64_INSN_FUNCS(msr_imm,	0xFFF8F01F, 0xD500401F)
 __AARCH64_INSN_FUNCS(msr_reg,	0xFFF00000, 0xD5100000)
diff --git a/arch/arm64/kernel/insn.c b/arch/arm64/kernel/insn.c
index a107375005bc..27d5a52d5058 100644
--- a/arch/arm64/kernel/insn.c
+++ b/arch/arm64/kernel/insn.c
@@ -176,7 +176,7 @@ bool __kprobes aarch64_insn_uses_literal(u32 insn)
 
 bool __kprobes aarch64_insn_is_branch(u32 insn)
 {
-	/* b, bl, cb*, tb*, b.cond, br, blr */
+	/* b, bl, cb*, tb*, ret*, b.cond, br*, blr* */
 
 	return aarch64_insn_is_b(insn) ||
 		aarch64_insn_is_bl(insn) ||
@@ -185,9 +185,19 @@ bool __kprobes aarch64_insn_is_branch(u32 insn)
 		aarch64_insn_is_tbz(insn) ||
 		aarch64_insn_is_tbnz(insn) ||
 		aarch64_insn_is_ret(insn) ||
+		aarch64_insn_is_retaa(insn) ||
+		aarch64_insn_is_retab(insn) ||
 		aarch64_insn_is_br(insn) ||
 		aarch64_insn_is_blr(insn) ||
-		aarch64_insn_is_bcond(insn);
+		aarch64_insn_is_bcond(insn) ||
+		aarch64_insn_is_braaz(insn) ||
+		aarch64_insn_is_brabz(insn) ||
+		aarch64_insn_is_braa(insn) ||
+		aarch64_insn_is_brab(insn) ||
+		aarch64_insn_is_blraaz(insn) ||
+		aarch64_insn_is_blrabz(insn) ||
+		aarch64_insn_is_blraa(insn) ||
+		aarch64_insn_is_blrab(insn);
 }
 
 int __kprobes aarch64_insn_patch_text_nosync(void *addr, u32 insn)
diff --git a/arch/arm64/kernel/probes/decode-insn.c b/arch/arm64/kernel/probes/decode-insn.c
index 263d5fba4c8a..f9eb8210d6d3 100644
--- a/arch/arm64/kernel/probes/decode-insn.c
+++ b/arch/arm64/kernel/probes/decode-insn.c
@@ -29,7 +29,9 @@ static bool __kprobes aarch64_insn_is_steppable(u32 insn)
 		    aarch64_insn_is_msr_imm(insn) ||
 		    aarch64_insn_is_msr_reg(insn) ||
 		    aarch64_insn_is_exception(insn) ||
-		    aarch64_insn_is_eret(insn))
+		    aarch64_insn_is_eret(insn) ||
+		    aarch64_insn_is_eretaa(insn) ||
+		    aarch64_insn_is_eretab(insn))
 			return false;
 
 		/*
-- 
2.17.1