Subject: [PATCH 2/2] powerpc/uprobes: Reject uprobe on a system call instruction

From: Nicholas Piggin <[email-masked]>
Date: Mon, 24 Jan 2022 15:57:41 +1000

Per the ISA, a Trace interrupt is not generated for a system call
[vectored] instruction. Reject uprobes on such instructions as we are
not emulating a system call [vectored] instruction anymore.

Signed-off-by: Naveen N. Rao <[email-masked]>
[np: Switch to pr_info_ratelimited]
Signed-off-by: Nicholas Piggin <[email-masked]>
---
 arch/powerpc/include/asm/ppc-opcode.h | 1 +
 arch/powerpc/kernel/uprobes.c         | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h
index 9675303b724e..8bbe16ce5173 100644
--- a/arch/powerpc/include/asm/ppc-opcode.h
+++ b/arch/powerpc/include/asm/ppc-opcode.h
@@ -411,6 +411,7 @@
 #define PPC_RAW_DCBFPS(a, b)		(0x7c0000ac | ___PPC_RA(a) | ___PPC_RB(b) | (4 << 21))
 #define PPC_RAW_DCBSTPS(a, b)		(0x7c0000ac | ___PPC_RA(a) | ___PPC_RB(b) | (6 << 21))
 #define PPC_RAW_SC()			(0x44000002)
+#define PPC_RAW_SCV()			(0x44000001)
 #define PPC_RAW_SYNC()			(0x7c0004ac)
 #define PPC_RAW_ISYNC()			(0x4c00012c)
 
diff --git a/arch/powerpc/kernel/uprobes.c b/arch/powerpc/kernel/uprobes.c
index c6975467d9ff..3779fde804bd 100644
--- a/arch/powerpc/kernel/uprobes.c
+++ b/arch/powerpc/kernel/uprobes.c
@@ -41,6 +41,12 @@ int arch_uprobe_analyze_insn(struct arch_uprobe *auprobe,
 	if (addr & 0x03)
 		return -EINVAL;
 
+	if (ppc_inst_val(ppc_inst_read(auprobe->insn)) == PPC_RAW_SC() ||
+	    ppc_inst_val(ppc_inst_read(auprobe->insn)) == PPC_RAW_SCV()) {
+		pr_info_ratelimited("Rejecting uprobe on system call instruction\n");
+		return -EINVAL;
+	}
+
 	if (cpu_has_feature(CPU_FTR_ARCH_31) &&
 	    ppc_inst_prefixed(ppc_inst_read(auprobe->insn)) &&
 	    (addr & 0x3f) == 60) {
-- 
2.23.0