Re: [PATCH v2 16/15] syscall_get_arch: add "struct task_struct *" argument

Dmitry V. Levin
2018-11-21T19:00:16Z

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Hi Paul,

On Wed, Nov 21, 2018 at 06:40:06PM +0000, Paul Burton wrote:
> Hi Dmitry,
>
> On Wed, Nov 21, 2018 at 03:44:22AM +0300, Dmitry V. Levin wrote:
> > This argument is required to extend the generic ptrace API
> > with PTRACE_GET_SYSCALL_INFO request: syscall_get_arch() is going to be
> > called from ptrace_request() along with other syscall_get_* functions
> > with a tracee as their argument.
> >
> > This change partially reverts commit 5e937a9ae913 ("syscall_get_arch:
> > remove useless function arguments").
> >
> >%
> >
> > diff --git a/arch/mips/include/asm/syscall.h b/arch/mips/include/asm/syscall.h
> > index 0170602a1e4e..52b633f20abd 100644
> > --- a/arch/mips/include/asm/syscall.h
> > +++ b/arch/mips/include/asm/syscall.h
> > @@ -73,7 +73,7 @@ static inline unsigned long mips_get_syscall_arg(unsigned long *arg,
> > #ifdef CONFIG_64BIT
> > case 4: case 5: case 6: case 7:
> > #ifdef CONFIG_MIPS32_O32
> > - if (test_thread_flag(TIF_32BIT_REGS))
> > + if (test_ti_thread_flag(task_thread_info(task), TIF_32BIT_REGS))
> > return get_user(*arg, (int *)usp + n);
> > else
> > #endif
>
> This ought to be test_tsk_thread_flag(task, TIF_32BIT_REGS) instead of
> open-coding test_tsk_thread_flag.

This will be corrected, thanks for letting me know.

> More fundamentally though, this change doesn't seem to be (directly)
> related to the change you describe in the commit message - it's not
> syscall_get_arch being modified here. I suspect this should be a
> separate commit, or if not please explain in the commit message why this
> change is included.

Good point, this is a fix that should not have been included into this commit.
The bug was found while preparing the syscall_get_arch change, and this
hunk just slipped in. I'll send it as a separate commit.

> Compounding the lack of clarity is the fact that I only received this
> patch, not the whole series, so I can't view the change in the context
> of the rest of the series.
>
> > @@ -140,14 +140,14 @@ extern const unsigned long sys_call_table[];
> > extern const unsigned long sys32_call_table[];
> > extern const unsigned long sysn32_call_table[];
> >
> > -static inline int syscall_get_arch(void)
> > +static inline int syscall_get_arch(struct task_struct *task)
> > {
> > int arch = AUDIT_ARCH_MIPS;
> > #ifdef CONFIG_64BIT
> > - if (!test_thread_flag(TIF_32BIT_REGS)) {
> > + if (!test_ti_thread_flag(task_thread_info(task), TIF_32BIT_REGS)) {
> > arch |= __AUDIT_ARCH_64BIT;
> > /* N32 sets only TIF_32BIT_ADDR */
> > - if (test_thread_flag(TIF_32BIT_ADDR))
> > + if (test_ti_thread_flag(task_thread_info(task), TIF_32BIT_ADDR))
> > arch |= __AUDIT_ARCH_CONVENTION_MIPS64_N32;
> > }
> > #endif
>
> This does seem like the described change, but there are 2 more instances
> of open-coding test_tsk_thread_flag which ought to be cleaned up.

This will be cleaned up, thanks for letting me know.

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