Re: [PATCH v4 3/4] powerpc/64: make buildable without CONFIG_COMPAT

From: Michal SuchÃnek
Date: Thu Aug 29 2019 - 14:56:15 EST

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In reply to: Christophe Leroy: "Re: [PATCH v4 3/4] powerpc/64: make buildable without CONFIG_COMPAT"
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On Thu, 29 Aug 2019 19:40:55 +0200
Christophe Leroy <christophe.leroy@xxxxxx> wrote:

> Le 29/08/2019 Ã 12:23, Michal Suchanek a ÃcritÂ:
> > There are numerous references to 32bit functions in generic and 64bit
> > code so ifdef them out.
> >
> > Signed-off-by: Michal Suchanek <msuchanek@xxxxxxx>
> > ---
> > v2:
> > - fix 32bit ifdef condition in signal.c
> > - simplify the compat ifdef condition in vdso.c - 64bit is redundant
> > - simplify the compat ifdef condition in callchain.c - 64bit is redundant
> > v3:
> > - use IS_ENABLED and maybe_unused where possible
> > - do not ifdef declarations
> > - clean up Makefile
> > v4:
> > - further makefile cleanup
> > - simplify is_32bit_task conditions
> > - avoid ifdef in condition by using return
> > ---
> > arch/powerpc/include/asm/thread_info.h | 4 ++--
> > arch/powerpc/kernel/Makefile | 7 +++----
> > arch/powerpc/kernel/entry_64.S | 2 ++
> > arch/powerpc/kernel/signal.c | 3 +--
> > arch/powerpc/kernel/syscall_64.c | 6 ++----
> > arch/powerpc/kernel/vdso.c | 5 ++---
> > arch/powerpc/perf/callchain.c | 14 ++++++++++----
> > 7 files changed, 22 insertions(+), 19 deletions(-)
> >
> > diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
> > index 8e1d0195ac36..c128d8a48ea3 100644
> > --- a/arch/powerpc/include/asm/thread_info.h
> > +++ b/arch/powerpc/include/asm/thread_info.h
> > @@ -144,10 +144,10 @@ static inline bool test_thread_local_flags(unsigned int flags)
> > return (ti->local_flags & flags) != 0;
> > }
> >
> > -#ifdef CONFIG_PPC64
> > +#ifdef CONFIG_COMPAT
> > #define is_32bit_task() (test_thread_flag(TIF_32BIT))
> > #else
> > -#define is_32bit_task() (1)
> > +#define is_32bit_task() (IS_ENABLED(CONFIG_PPC32))
> > #endif
> >
> > #if defined(CONFIG_PPC64)
> > diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> > index 1d646a94d96c..9d8772e863b9 100644
> > --- a/arch/powerpc/kernel/Makefile
> > +++ b/arch/powerpc/kernel/Makefile
> > @@ -44,16 +44,15 @@ CFLAGS_btext.o += -DDISABLE_BRANCH_PROFILING
> > endif
> >
> > obj-y := cputable.o ptrace.o syscalls.o \
> > - irq.o align.o signal_32.o pmc.o vdso.o \
> > + irq.o align.o signal_$(BITS).o pmc.o vdso.o \
> > process.o systbl.o idle.o \
> > signal.o sysfs.o cacheinfo.o time.o \
> > prom.o traps.o setup-common.o \
> > udbg.o misc.o io.o misc_$(BITS).o \
> > of_platform.o prom_parse.o
> > -obj-$(CONFIG_PPC64) += setup_64.o sys_ppc32.o \
> > - signal_64.o ptrace32.o \
> > - paca.o nvram_64.o firmware.o \
> > +obj-$(CONFIG_PPC64) += setup_64.o paca.o nvram_64.o firmware.o \
> > syscall_64.o
> > +obj-$(CONFIG_COMPAT) += sys_ppc32.o ptrace32.o signal_32.o
> > obj-$(CONFIG_VDSO32) += vdso32/
> > obj-$(CONFIG_PPC_WATCHDOG) += watchdog.o
> > obj-$(CONFIG_HAVE_HW_BREAKPOINT) += hw_breakpoint.o
> > diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
> > index 2ec825a85f5b..a2dbf216f607 100644
> > --- a/arch/powerpc/kernel/entry_64.S
> > +++ b/arch/powerpc/kernel/entry_64.S
> > @@ -51,8 +51,10 @@
> > SYS_CALL_TABLE:
> > .tc sys_call_table[TC],sys_call_table
> >
> > +#ifdef CONFIG_COMPAT
> > COMPAT_SYS_CALL_TABLE:
> > .tc compat_sys_call_table[TC],compat_sys_call_table
> > +#endif
> >
> > /* This value is used to mark exception frames on the stack. */
> > exception_marker:
> > diff --git a/arch/powerpc/kernel/signal.c b/arch/powerpc/kernel/signal.c
> > index 60436432399f..61678cb0e6a1 100644
> > --- a/arch/powerpc/kernel/signal.c
> > +++ b/arch/powerpc/kernel/signal.c
> > @@ -247,7 +247,6 @@ static void do_signal(struct task_struct *tsk)
> > sigset_t *oldset = sigmask_to_save();
> > struct ksignal ksig = { .sig = 0 };
> > int ret;
> > - int is32 = is_32bit_task();
> >
> > BUG_ON(tsk != current);
> >
> > @@ -277,7 +276,7 @@ static void do_signal(struct task_struct *tsk)
> >
> > rseq_signal_deliver(&ksig, tsk->thread.regs);
> >
> > - if (is32) {
> > + if (is_32bit_task()) {
> > if (ksig.ka.sa.sa_flags & SA_SIGINFO)
> > ret = handle_rt_signal32(&ksig, oldset, tsk);
> > else
> > diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
> > index 98ed970796d5..0d5cbbe54cf1 100644
> > --- a/arch/powerpc/kernel/syscall_64.c
> > +++ b/arch/powerpc/kernel/syscall_64.c
> > @@ -38,7 +38,6 @@ typedef long (*syscall_fn)(long, long, long, long, long, long);
> >
> > long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8, unsigned long r0, struct pt_regs *regs)
> > {
> > - unsigned long ti_flags;
> > syscall_fn f;
> >
> > BUG_ON(!(regs->msr & MSR_PR));
> > @@ -83,8 +82,7 @@ long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
> > */
> > regs->softe = IRQS_ENABLED;
> >
> > - ti_flags = current_thread_info()->flags;
> > - if (unlikely(ti_flags & _TIF_SYSCALL_DOTRACE)) {
> > + if (unlikely(current_thread_info()->flags & _TIF_SYSCALL_DOTRACE)) {
> > /*
> > * We use the return value of do_syscall_trace_enter() as the
> > * syscall number. If the syscall was rejected for any reason
> > @@ -100,7 +98,7 @@ long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
> > /* May be faster to do array_index_nospec? */
> > barrier_nospec();
> >
> > - if (unlikely(ti_flags & _TIF_32BIT)) {
> > + if (unlikely(is_32bit_task())) {
> > f = (void *)compat_sys_call_table[r0];
> >
> > r3 &= 0x00000000ffffffffULL;
> > diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
> > index d60598113a9f..6d4a077f74d6 100644
> > --- a/arch/powerpc/kernel/vdso.c
> > +++ b/arch/powerpc/kernel/vdso.c
> > @@ -667,9 +667,7 @@ static void __init vdso_setup_syscall_map(void)
> > {
> > unsigned int i;
> > extern unsigned long *sys_call_table;
> > -#ifdef CONFIG_PPC64
> > extern unsigned long *compat_sys_call_table;
> > -#endif
> > extern unsigned long sys_ni_syscall;
> >
> >
> > @@ -678,7 +676,8 @@ static void __init vdso_setup_syscall_map(void)
> > if (sys_call_table[i] != sys_ni_syscall)
> > vdso_data->syscall_map_64[i >> 5] |=
> > 0x80000000UL >> (i & 0x1f);
> > - if (compat_sys_call_table[i] != sys_ni_syscall)
> > + if (IS_ENABLED(CONFIG_COMPAT) &&
> > + compat_sys_call_table[i] != sys_ni_syscall)
> > vdso_data->syscall_map_32[i >> 5] |=
> > 0x80000000UL >> (i & 0x1f);
> > #else /* CONFIG_PPC64 */
> > diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
> > index c84bbd4298a0..aef8c750d242 100644
> > --- a/arch/powerpc/perf/callchain.c
> > +++ b/arch/powerpc/perf/callchain.c
> > @@ -15,7 +15,7 @@
> > #include <asm/sigcontext.h>
> > #include <asm/ucontext.h>
> > #include <asm/vdso.h>
> > -#ifdef CONFIG_PPC64
> > +#ifdef CONFIG_COMPAT
>
> Is this ifdef needed at all ? Is it a problem to include it all the time ?

Yes, it is a problem. Some 32bit structures are not defined giving an
error.

>
> > #include "../kernel/ppc32.h"
> > #endif
> > #include <asm/pte-walk.h>
> > @@ -165,6 +165,7 @@ static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
> > return read_user_stack_slow(ptr, ret, 8);
> > }
> >
> > +__maybe_unused
>
> I don't like that too much. I see this function is almost identical
> between PPC64 and PPC32. It should be possible to have only one, using
> IS_ENABLED(CONFIG_PPC64) inside it to call read_user_stack_slow().
> An define a dummy read_user_stack_slow() for PPC32 as already done for
> perf_callchain_user_64().

We need to #ifdef the block below anyway because it needs 32bit
structures defined which aren't. So can add usage there.

>
> > static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
> > {
> > if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
> > @@ -341,6 +342,7 @@ static inline int valid_user_sp(unsigned long sp, int is_64)
> >
> > #endif /* CONFIG_PPC64 */
> >
> > +#if defined(CONFIG_PPC32) || defined(CONFIG_COMPAT)
> > /*
> > * Layout for non-RT signal frames
> > */
> > @@ -482,12 +484,16 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
> > sp = next_sp;
> > }
> > }
> > +#endif /* 32bit */
> >
> > void
> > perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
> > {
> > - if (current_is_64bit())
> > - perf_callchain_user_64(entry, regs);
> > - else
> > +#if defined(CONFIG_PPC32) || defined(CONFIG_COMPAT)
> > + if (!current_is_64bit()) {
> > perf_callchain_user_32(entry, regs);
> > + return;
> > + }
> > +#endif
> > + perf_callchain_user_64(entry, regs);
> > }
> >
>
> Instead of that it could just be:
>
> if (current_is_64bit())
> perf_callchain_user_64(entry, regs);
> else
> perf_callchain_user_32(entry, regs);
>
>
> By adding a dummy perf_callchain_user_32() when needed as already done
> for perf_callchain_user_64()

and it can do a dummy use of the function above as well.

> And by making sure current_is_64bit() returns IS_ENABLED(CONFIG_PPC64)
> when CONFIG_COMPAT is not set, on the same principle as you did for
> is_32bit_task()
Yes, that would make it constant for the !COMPAT cases.
>
> And maybe you could think about spliting callchain.c out in a
> callchain_32.c and a callchain_64.c that gets selected by the Makefiles
> based on the same principle as you did for ptrace_32.c etc...

I actually did not split those. Can look how splitting is done there
and if it can be applied to the callchain situation.

Thanks

Michal

Next message: Ingo Molnar: "Re: [GIT PULL] perf/core improvements and fixes"
Previous message: tip-bot2 for Thomas Gleixner: "[tip: x86/urgent] x86/mm/cpa: Prevent large page split when ftrace flips RW on kernel text"
In reply to: Christophe Leroy: "Re: [PATCH v4 3/4] powerpc/64: make buildable without CONFIG_COMPAT"
Next in thread: Michal Suchanek: "[PATCH v4 2/4] powerpc: move common register copy functions from signal_32.c to signal.c"
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