From: Amit Daniel Kachhap amit.kachhap@arm.com
[ Upstream commit 93396936ed0ce2c6f44140bd14728611d0bb065e ]
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 group definitions of all such instructions and rejecting their probes. The instruction groups added are br_auth(braa, brab, braaz and brabz), blr_auth(blraa, blrab, blraaz and blrabz), ret_auth(retaa and retab) and eret_auth(eretaa and eretab).
Warning log: WARNING: CPU: 0 PID: 156 at arch/arm64/kernel/probes/uprobes.c:182 uprobe_single_step_handler+0x34/0x50 Modules linked in: CPU: 0 PID: 156 Comm: func Not tainted 5.9.0-rc3 #188 Hardware name: Foundation-v8A (DT) pstate: 804003c9 (Nzcv DAIF +PAN -UAO BTYPE=--) pc : uprobe_single_step_handler+0x34/0x50 lr : single_step_handler+0x70/0xf8 sp : ffff800012af3e30 x29: ffff800012af3e30 x28: ffff000878723b00 x27: 0000000000000000 x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000 x23: 0000000060001000 x22: 00000000cb000022 x21: ffff800012065ce8 x20: ffff800012af3ec0 x19: ffff800012068d50 x18: 0000000000000000 x17: 0000000000000000 x16: 0000000000000000 x15: 0000000000000000 x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000000 x10: 0000000000000000 x9 : ffff800010085c90 x8 : 0000000000000000 x7 : 0000000000000000 x6 : ffff80001205a9c8 x5 : ffff80001205a000 x4 : ffff80001233db80 x3 : ffff8000100a7a60 x2 : 0020000000000003 x1 : 0000fffffffff008 x0 : ffff800012af3ec0 Call trace: uprobe_single_step_handler+0x34/0x50 single_step_handler+0x70/0xf8 do_debug_exception+0xb8/0x130 el0_sync_handler+0x138/0x1b8 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@arm.com Reviewed-by: Dave Martin Dave.Martin@arm.com Link: https://lore.kernel.org/r/20200914083656.21428-2-amit.kachhap@arm.com Signed-off-by: Will Deacon will@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- arch/arm64/include/asm/insn.h | 4 ++++ arch/arm64/kernel/insn.c | 5 ++++- arch/arm64/kernel/probes/decode-insn.c | 3 ++- 3 files changed, 10 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/insn.h b/arch/arm64/include/asm/insn.h index 0bc46149e4917..4b39293d0f72d 100644 --- a/arch/arm64/include/asm/insn.h +++ b/arch/arm64/include/asm/insn.h @@ -359,9 +359,13 @@ __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(br_auth, 0xFEFFF800, 0xD61F0800) __AARCH64_INSN_FUNCS(blr, 0xFFFFFC1F, 0xD63F0000) +__AARCH64_INSN_FUNCS(blr_auth, 0xFEFFF800, 0xD63F0800) __AARCH64_INSN_FUNCS(ret, 0xFFFFFC1F, 0xD65F0000) +__AARCH64_INSN_FUNCS(ret_auth, 0xFFFFFBFF, 0xD65F0BFF) __AARCH64_INSN_FUNCS(eret, 0xFFFFFFFF, 0xD69F03E0) +__AARCH64_INSN_FUNCS(eret_auth, 0xFFFFFBFF, 0xD69F0BFF) __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 a107375005bc9..ccc8c9e22b258 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) || @@ -185,8 +185,11 @@ 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_ret_auth(insn) || aarch64_insn_is_br(insn) || + aarch64_insn_is_br_auth(insn) || aarch64_insn_is_blr(insn) || + aarch64_insn_is_blr_auth(insn) || aarch64_insn_is_bcond(insn); }
diff --git a/arch/arm64/kernel/probes/decode-insn.c b/arch/arm64/kernel/probes/decode-insn.c index 263d5fba4c8a3..c541fb48886e3 100644 --- a/arch/arm64/kernel/probes/decode-insn.c +++ b/arch/arm64/kernel/probes/decode-insn.c @@ -29,7 +29,8 @@ 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_eret_auth(insn)) return false;
/*