[PATCH v5 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. However the uprobe of such instructions leads
to kernel warnings in a loop as they are not explicitly checked.

This 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>
---
Changes since v4:
* New patch.

 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