linux-kernel - [PATCH v2 06/10] riscv: Allow ptrace control of the tagged address ABI

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Message-ID: <20240625210933.1620802-7-samuel.holland@sifive.com>
Date: Tue, 25 Jun 2024 14:09:17 -0700
From: Samuel Holland <samuel.holland@...ive.com>
To: Palmer Dabbelt <palmer@...belt.com>,
	linux-riscv@...ts.infradead.org
Cc: devicetree@...r.kernel.org,
	Catalin Marinas <catalin.marinas@....com>,
	linux-kernel@...r.kernel.org,
	Anup Patel <anup@...infault.org>,
	Conor Dooley <conor@...nel.org>,
	kasan-dev@...glegroups.com,
	Atish Patra <atishp@...shpatra.org>,
	Evgenii Stepanov <eugenis@...gle.com>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
	Samuel Holland <samuel.holland@...ive.com>
Subject: [PATCH v2 06/10] riscv: Allow ptrace control of the tagged address ABI

This allows a tracer to control the ABI of the tracee, as on arm64.

Signed-off-by: Samuel Holland <samuel.holland@...ive.com>
---

(no changes since v1)

 arch/riscv/kernel/ptrace.c | 42 ++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/elf.h   |  1 +
 2 files changed, 43 insertions(+)

diff --git a/arch/riscv/kernel/ptrace.c b/arch/riscv/kernel/ptrace.c
index 92731ff8c79a..f8ceecc562fe 100644
--- a/arch/riscv/kernel/ptrace.c
+++ b/arch/riscv/kernel/ptrace.c
@@ -28,6 +28,9 @@ enum riscv_regset {
 #ifdef CONFIG_RISCV_ISA_V
 	REGSET_V,
 #endif
+#ifdef CONFIG_RISCV_ISA_POINTER_MASKING
+	REGSET_TAGGED_ADDR_CTRL,
+#endif
 };
 
 static int riscv_gpr_get(struct task_struct *target,
@@ -152,6 +155,35 @@ static int riscv_vr_set(struct task_struct *target,
 }
 #endif
 
+#ifdef CONFIG_RISCV_ISA_POINTER_MASKING
+static int tagged_addr_ctrl_get(struct task_struct *target,
+				const struct user_regset *regset,
+				struct membuf to)
+{
+	long ctrl = get_tagged_addr_ctrl(target);
+
+	if (IS_ERR_VALUE(ctrl))
+		return ctrl;
+
+	return membuf_write(&to, &ctrl, sizeof(ctrl));
+}
+
+static int tagged_addr_ctrl_set(struct task_struct *target,
+				const struct user_regset *regset,
+				unsigned int pos, unsigned int count,
+				const void *kbuf, const void __user *ubuf)
+{
+	int ret;
+	long ctrl;
+
+	ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &ctrl, 0, -1);
+	if (ret)
+		return ret;
+
+	return set_tagged_addr_ctrl(target, ctrl);
+}
+#endif
+
 static const struct user_regset riscv_user_regset[] = {
 	[REGSET_X] = {
 		.core_note_type = NT_PRSTATUS,
@@ -182,6 +214,16 @@ static const struct user_regset riscv_user_regset[] = {
 		.set = riscv_vr_set,
 	},
 #endif
+#ifdef CONFIG_RISCV_ISA_POINTER_MASKING
+	[REGSET_TAGGED_ADDR_CTRL] = {
+		.core_note_type = NT_RISCV_TAGGED_ADDR_CTRL,
+		.n = 1,
+		.size = sizeof(long),
+		.align = sizeof(long),
+		.regset_get = tagged_addr_ctrl_get,
+		.set = tagged_addr_ctrl_set,
+	},
+#endif
 };
 
 static const struct user_regset_view riscv_user_native_view = {
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index b54b313bcf07..9a32532d7264 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -448,6 +448,7 @@ typedef struct elf64_shdr {
 #define NT_MIPS_MSA	0x802		/* MIPS SIMD registers */
 #define NT_RISCV_CSR	0x900		/* RISC-V Control and Status Registers */
 #define NT_RISCV_VECTOR	0x901		/* RISC-V vector registers */
+#define NT_RISCV_TAGGED_ADDR_CTRL 0x902	/* RISC-V tagged address control (prctl()) */
 #define NT_LOONGARCH_CPUCFG	0xa00	/* LoongArch CPU config registers */
 #define NT_LOONGARCH_CSR	0xa01	/* LoongArch control and status registers */
 #define NT_LOONGARCH_LSX	0xa02	/* LoongArch Loongson SIMD Extension registers */
-- 
2.44.1