linux-kernel - [PATCH 1/3] arm64: ptrace: Add is_syscall

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Message-Id: <20210416075533.7720-1-zhe.he@windriver.com>
Date:   Fri, 16 Apr 2021 15:55:31 +0800
From:   He Zhe <zhe.he@...driver.com>
To:     oleg@...hat.com, catalin.marinas@....com, will@...nel.org,
        linux-arm-kernel@...ts.infradead.org, paul@...l-moore.com,
        eparis@...hat.com, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org, zhe.he@...driver.com
Subject: [PATCH 1/3] arm64: ptrace: Add is_syscall_success to handle compat

The general version of is_syscall_success does not handle 32-bit
compatible case, which would cause 32-bit negative return code to be
recoganized as a positive number later and seen as a "success".

Since is_compat_thread is defined in compat.h, implementing
is_syscall_success in ptrace.h would introduce build failure due to
recursive inclusion of some basic headers like mutex.h. We put the
implementation to ptrace.c

Signed-off-by: He Zhe <zhe.he@...driver.com>
---
 arch/arm64/include/asm/ptrace.h |  3 +++
 arch/arm64/kernel/ptrace.c      | 10 ++++++++++
 2 files changed, 13 insertions(+)

diff --git a/arch/arm64/include/asm/ptrace.h b/arch/arm64/include/asm/ptrace.h
index e58bca832dff..3c415e9e5d85 100644
--- a/arch/arm64/include/asm/ptrace.h
+++ b/arch/arm64/include/asm/ptrace.h
@@ -328,6 +328,9 @@ static inline void regs_set_return_value(struct pt_regs *regs, unsigned long rc)
 	regs->regs[0] = rc;
 }
 
+extern inline int is_syscall_success(struct pt_regs *regs);
+#define is_syscall_success(regs) is_syscall_success(regs)
+
 /**
  * regs_get_kernel_argument() - get Nth function argument in kernel
  * @regs:	pt_regs of that context
diff --git a/arch/arm64/kernel/ptrace.c b/arch/arm64/kernel/ptrace.c
index 170f42fd6101..3266201f8c60 100644
--- a/arch/arm64/kernel/ptrace.c
+++ b/arch/arm64/kernel/ptrace.c
@@ -1909,3 +1909,13 @@ int valid_user_regs(struct user_pt_regs *regs, struct task_struct *task)
 	else
 		return valid_native_regs(regs);
 }
+
+inline int is_syscall_success(struct pt_regs *regs)
+{
+	unsigned long val = regs->regs[0];
+
+	if (is_compat_thread(task_thread_info(current)))
+		val = sign_extend64(val, 31);
+
+	return !IS_ERR_VALUE(val);
+}
-- 
2.17.1