linux-kernel - [PATCH v5 16/25] powerpc: define syscall_get

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Message-ID: <20181210043026.GP6131@altlinux.org>
Date:   Mon, 10 Dec 2018 07:30:26 +0300
From:   "Dmitry V. Levin" <ldv@...linux.org>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Oleg Nesterov <oleg@...hat.com>,
        Andy Lutomirski <luto@...nel.org>
Cc:     Elvira Khabirova <lineprinter@...linux.org>,
        Eugene Syromyatnikov <esyr@...hat.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH v5 16/25] powerpc: define syscall_get_error()

syscall_get_error() is required to be implemented on this
architecture in addition to already implemented syscall_get_nr(),
syscall_get_arguments(), syscall_get_return_value(), and
syscall_get_arch() functions in order to extend the generic
ptrace API with PTRACE_GET_SYSCALL_INFO request.

Cc: Michael Ellerman <mpe@...erman.id.au>
Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Oleg Nesterov <oleg@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Elvira Khabirova <lineprinter@...linux.org>
Cc: Eugene Syromyatnikov <esyr@...hat.com>
Cc: linuxppc-dev@...ts.ozlabs.org
Signed-off-by: Dmitry V. Levin <ldv@...linux.org>
---

Notes:
    This change has been tested with
    tools/testing/selftests/ptrace/get_syscall_info.c and strace,
    so it's correct from PTRACE_GET_SYSCALL_INFO point of view.
    
    This cast doubts on commit v4.3-rc1~86^2~81 that changed
    syscall_set_return_value() in a way that doesn't quite match
    syscall_get_error(), but syscall_set_return_value() is out
    of scope of this series, so I just air my concerns.

 arch/powerpc/include/asm/syscall.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
index ab9f3f0a8637..1d03e753391d 100644
--- a/arch/powerpc/include/asm/syscall.h
+++ b/arch/powerpc/include/asm/syscall.h
@@ -39,6 +39,16 @@ static inline void syscall_rollback(struct task_struct *task,
 	regs->gpr[3] = regs->orig_gpr3;
 }
 
+static inline long syscall_get_error(struct task_struct *task,
+				     struct pt_regs *regs)
+{
+	/*
+	 * If the system call failed,
+	 * regs->gpr[3] contains a positive ERRORCODE.
+	 */
+	return (regs->ccr & 0x10000000UL) ? -regs->gpr[3] : 0;
+}
+
 static inline long syscall_get_return_value(struct task_struct *task,
 					    struct pt_regs *regs)
 {
-- 
ldv