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    Subject[PATCH 5.19 171/365] nios2: add force_successful_syscall_return()
    Date
    From: Al Viro <viro@zeniv.linux.org.uk>

    commit fd0c153daad135d0ec1a53c5dbe6936a724d6ae1 upstream.

    If we use the ancient SysV syscall ABI, we'd better have tell the
    kernel how to claim that a negative return value is a success.
    Use ->orig_r2 for that - it's inaccessible via ptrace, so it's
    a fair game for changes and it's normally[*] non-negative on return
    from syscall. Set to -1; syscall is not going to be restart-worthy
    by definition, so we won't interfere with that use either.

    [*] the only exception is rt_sigreturn(), where we skip the entire
    messing with r1/r2 anyway.

    Fixes: 82ed08dd1b0e ("nios2: Exception handling")
    Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    arch/nios2/include/asm/ptrace.h | 2 ++
    arch/nios2/kernel/entry.S | 6 ++++++
    2 files changed, 8 insertions(+)

    --- a/arch/nios2/include/asm/ptrace.h
    +++ b/arch/nios2/include/asm/ptrace.h
    @@ -74,6 +74,8 @@ extern void show_regs(struct pt_regs *);
    ((struct pt_regs *)((unsigned long)current_thread_info() + THREAD_SIZE)\
    - 1)

    +#define force_successful_syscall_return() (current_pt_regs()->orig_r2 = -1)
    +
    int do_syscall_trace_enter(void);
    void do_syscall_trace_exit(void);
    #endif /* __ASSEMBLY__ */
    --- a/arch/nios2/kernel/entry.S
    +++ b/arch/nios2/kernel/entry.S
    @@ -213,6 +213,9 @@ local_restart:
    translate_rc_and_ret:
    movi r1, 0
    bge r2, zero, 3f
    + ldw r1, PT_ORIG_R2(sp)
    + addi r1, r1, 1
    + beq r1, zero, 3f
    sub r2, zero, r2
    movi r1, 1
    3:
    @@ -276,6 +279,9 @@ traced_system_call:
    translate_rc_and_ret2:
    movi r1, 0
    bge r2, zero, 4f
    + ldw r1, PT_ORIG_R2(sp)
    + addi r1, r1, 1
    + beq r1, zero, 4f
    sub r2, zero, r2
    movi r1, 1
    4:

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