linux-kernel - [PATCH 1/4] arm64: expose orig_x0 in the user_pt

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Message-Id: <20210322225053.428615-2-avagin@gmail.com>
Date:   Mon, 22 Mar 2021 15:50:50 -0700
From:   Andrei Vagin <avagin@...il.com>
To:     Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>
Cc:     Oleg Nesterov <oleg@...hat.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Andrei Vagin <avagin@...il.com>,
        Dave Martin <Dave.Martin@....com>,
        Keno Fischer <keno@...iacomputing.com>
Subject: [PATCH 1/4] arm64: expose orig_x0 in the user_pt_regs structure

orig_x0 is recorded at the start of the syscall entry and then it is
used for resetting the argument back to its original value during
syscall restarts.

If orig_x0 isn't available from user-space, this makes it tricky to
manage arguments of restarted system calls.

Cc: Keno Fischer <keno@...iacomputing.com>
Signed-off-by: Andrei Vagin <avagin@...il.com>
---
 arch/arm64/include/asm/ptrace.h      | 2 +-
 arch/arm64/include/uapi/asm/ptrace.h | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
index e58bca832dff..d4cdf98ac003 100644
--- a/arch/arm64/include/asm/ptrace.h
+++ b/arch/arm64/include/asm/ptrace.h
@@ -183,9 +183,9 @@ struct pt_regs {
 			u64 sp;
 			u64 pc;
 			u64 pstate;
+			u64 orig_x0;
 		};
 	};
-	u64 orig_x0;
 #ifdef __AARCH64EB__
 	u32 unused2;
 	s32 syscallno;
diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h
index 758ae984ff97..3c118c5b0893 100644
--- a/arch/arm64/include/uapi/asm/ptrace.h
+++ b/arch/arm64/include/uapi/asm/ptrace.h
@@ -90,6 +90,7 @@ struct user_pt_regs {
 	__u64		sp;
 	__u64		pc;
 	__u64		pstate;
+	__u64		orig_x0;
 };
 
 struct user_fpsimd_state {
-- 
2.29.2