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From:   Andrei Vagin <avagin@gmail.com>
To:     Will Deacon <will@kernel.org>,
        Catalin Marinas <catalin.marinas@arm.com>
Cc:     Oleg Nesterov <oleg@redhat.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Andrei Vagin <avagin@gmail.com>
Subject: [PATCH 2/3] arm64/ptrace: introduce NT_ARM_PRSTATUS to get a full set of registers
Date:   Tue, 19 Jan 2021 14:06:36 -0800
Message-Id: <20210119220637.494476-3-avagin@gmail.com>
In-Reply-To: <20210119220637.494476-1-avagin@gmail.com>
References: <20210119220637.494476-1-avagin@gmail.com>
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This is an alternative to NT_PRSTATUS that clobbers ip/r12 on AArch32,
x7 on AArch64 when a tracee is stopped in syscall entry or syscall exit
traps.

Signed-off-by: Andrei Vagin <avagin@gmail.com>
---
 arch/arm64/kernel/ptrace.c | 39 ++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/elf.h   |  1 +
 2 files changed, 40 insertions(+)

diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 1863f080cb07..b8e4c2ddf636 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -591,6 +591,15 @@ static int gpr_get(struct task_struct *target,
 	return ret;
 }
 
+static int gpr_get_full(struct task_struct *target,
+		   const struct user_regset *regset,
+		   struct membuf to)
+{
+	struct user_pt_regs *uregs = &task_pt_regs(target)->user_regs;
+
+	return membuf_write(&to, uregs, sizeof(*uregs));
+}
+
 static int gpr_set(struct task_struct *target, const struct user_regset *regset,
 		   unsigned int pos, unsigned int count,
 		   const void *kbuf, const void __user *ubuf)
@@ -1088,6 +1097,7 @@ static int tagged_addr_ctrl_set(struct task_struct *target, const struct
 
 enum aarch64_regset {
 	REGSET_GPR,
+	REGSET_GPR_FULL,
 	REGSET_FPR,
 	REGSET_TLS,
 #ifdef CONFIG_HAVE_HW_BREAKPOINT
@@ -1119,6 +1129,14 @@ static const struct user_regset aarch64_regsets[] = {
 		.regset_get = gpr_get,
 		.set = gpr_set
 	},
+	[REGSET_GPR_FULL] = {
+		.core_note_type = NT_ARM_PRSTATUS,
+		.n = sizeof(struct user_pt_regs) / sizeof(u64),
+		.size = sizeof(u64),
+		.align = sizeof(u64),
+		.regset_get = gpr_get_full,
+		.set = gpr_set
+	},
 	[REGSET_FPR] = {
 		.core_note_type = NT_PRFPREG,
 		.n = sizeof(struct user_fpsimd_state) / sizeof(u32),
@@ -1225,6 +1243,7 @@ static const struct user_regset_view user_aarch64_view = {
 #ifdef CONFIG_COMPAT
 enum compat_regset {
 	REGSET_COMPAT_GPR,
+	REGSET_COMPAT_GPR_FULL,
 	REGSET_COMPAT_VFP,
 };
 
@@ -1285,6 +1304,18 @@ static int compat_gpr_get(struct task_struct *target,
 	return 0;
 }
 
+/* compat_gpr_get_full doesn't  overwrite x12 like compat_gpr_get. */
+static int compat_gpr_get_full(struct task_struct *target,
+			  const struct user_regset *regset,
+			  struct membuf to)
+{
+	int i = 0;
+
+	while (to.left)
+		membuf_store(&to, compat_get_user_reg(target, i++));
+	return 0;
+}
+
 static int compat_gpr_set(struct task_struct *target,
 			  const struct user_regset *regset,
 			  unsigned int pos, unsigned int count,
@@ -1435,6 +1466,14 @@ static const struct user_regset aarch32_regsets[] = {
 		.regset_get = compat_gpr_get,
 		.set = compat_gpr_set
 	},
+	[REGSET_COMPAT_GPR_FULL] = {
+		.core_note_type = NT_ARM_PRSTATUS,
+		.n = COMPAT_ELF_NGREG,
+		.size = sizeof(compat_elf_greg_t),
+		.align = sizeof(compat_elf_greg_t),
+		.regset_get = compat_gpr_get_full,
+		.set = compat_gpr_set
+	},
 	[REGSET_COMPAT_VFP] = {
 		.core_note_type = NT_ARM_VFP,
 		.n = VFP_STATE_SIZE / sizeof(compat_ulong_t),
diff --git a/include/uapi/linux/elf.h b/include/uapi/linux/elf.h
index 30f68b42eeb5..a2086d19263a 100644
--- a/include/uapi/linux/elf.h
+++ b/include/uapi/linux/elf.h
@@ -426,6 +426,7 @@ typedef struct elf64_shdr {
 #define NT_ARM_PACA_KEYS	0x407	/* ARM pointer authentication address keys */
 #define NT_ARM_PACG_KEYS	0x408	/* ARM pointer authentication generic key */
 #define NT_ARM_TAGGED_ADDR_CTRL	0x409	/* arm64 tagged address control (prctl()) */
+#define NT_ARM_PRSTATUS		0x410   /* ARM general-purpose registers */
 #define NT_ARC_V2	0x600		/* ARCv2 accumulator/extra registers */
 #define NT_VMCOREDD	0x700		/* Vmcore Device Dump Note */
 #define NT_MIPS_DSP	0x800		/* MIPS DSP ASE registers */
-- 
2.29.2