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From:   Max Filippov <jcmvbkbc@gmail.com>
To:     linux-xtensa@linux-xtensa.org
Cc:     Chris Zankel <chris@zankel.net>, linux-kernel@vger.kernel.org,
        bpf@vger.kernel.org, netdev@vger.kernel.org,
        linux-kselftest@vger.kernel.org, Max Filippov <jcmvbkbc@gmail.com>
Subject: [PATCH 1/3] xtensa: expose syscall through user_pt_regs
Date:   Sat, 18 Jul 2020 19:16:52 -0700
Message-Id: <20200719021654.25922-2-jcmvbkbc@gmail.com>
In-Reply-To: <20200719021654.25922-1-jcmvbkbc@gmail.com>
References: <20200719021654.25922-1-jcmvbkbc@gmail.com>
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Use one of the reserved slots in struct user_pt_regs to return syscall
number in the GPR regset. Update syscall number from the GPR regset only
when it's non-zero.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
---
 arch/xtensa/include/uapi/asm/ptrace.h | 3 ++-
 arch/xtensa/kernel/ptrace.c           | 4 ++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/arch/xtensa/include/uapi/asm/ptrace.h b/arch/xtensa/include/uapi/asm/ptrace.h
index 2ec0f9100a06..50db3e0a6341 100644
--- a/arch/xtensa/include/uapi/asm/ptrace.h
+++ b/arch/xtensa/include/uapi/asm/ptrace.h
@@ -50,7 +50,8 @@ struct user_pt_regs {
 	__u32 windowstart;
 	__u32 windowbase;
 	__u32 threadptr;
-	__u32 reserved[7 + 48];
+	__u32 syscall;
+	__u32 reserved[6 + 48];
 	__u32 a[64];
 };
 
diff --git a/arch/xtensa/kernel/ptrace.c b/arch/xtensa/kernel/ptrace.c
index 0278d7dfb4d6..437b4297948d 100644
--- a/arch/xtensa/kernel/ptrace.c
+++ b/arch/xtensa/kernel/ptrace.c
@@ -52,6 +52,7 @@ static int gpr_get(struct task_struct *target,
 		.threadptr = regs->threadptr,
 		.windowbase = regs->windowbase,
 		.windowstart = regs->windowstart,
+		.syscall = regs->syscall,
 	};
 
 	memcpy(newregs.a,
@@ -91,6 +92,9 @@ static int gpr_set(struct task_struct *target,
 	regs->sar = newregs.sar;
 	regs->threadptr = newregs.threadptr;
 
+	if (newregs.syscall)
+		regs->syscall = newregs.syscall;
+
 	if (newregs.windowbase != regs->windowbase ||
 	    newregs.windowstart != regs->windowstart) {
 		u32 rotws, wmask;
-- 
2.20.1