Re: [PATCH v2 3/4] powerpc/64: make buildable without CONFIG_COMPAT

Christophe Leroy
2019-08-28T12:49:20Z

Le 28/08/2019 à 12:30, Michal Suchanek a écrit :
> There are numerous references to 32bit functions in generic and 64bit
> code so ifdef them out.

As far as possible, avoid opting things out with ifdefs. Ref
https://www.kernel.org/doc/html/latest/process/coding-style.html#conditional-compilation

See comment below.

>
> Signed-off-by: Michal Suchanek <msuchanek@suse.de>
> ---
> 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
> ---
> arch/powerpc/include/asm/syscall.h | 2 ++
> arch/powerpc/kernel/Makefile | 15 ++++++++++++---
> arch/powerpc/kernel/entry_64.S | 2 ++
> arch/powerpc/kernel/signal.c | 5 +++--
> arch/powerpc/kernel/syscall_64.c | 5 +++--
> arch/powerpc/kernel/vdso.c | 4 +++-
> arch/powerpc/perf/callchain.c | 14 ++++++++++----
> 7 files changed, 35 insertions(+), 12 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/syscall.h b/arch/powerpc/include/asm/syscall.h
> index 38d62acfdce7..3ed3b75541a1 100644
> --- a/arch/powerpc/include/asm/syscall.h
> +++ b/arch/powerpc/include/asm/syscall.h
> @@ -16,7 +16,9 @@
>
> /* ftrace syscalls requires exporting the sys_call_table */
> extern const unsigned long sys_call_table[];
> +#ifdef CONFIG_COMPAT
> extern const unsigned long compat_sys_call_table[];
> +#endif

Leaving the declaration should be harmless.

>
> static inline int syscall_get_nr(struct task_struct *task, struct pt_regs *regs)
> {
> diff --git a/arch/powerpc/kernel/Makefile b/arch/powerpc/kernel/Makefile
> index 1d646a94d96c..b0db365b83d8 100644
> --- a/arch/powerpc/kernel/Makefile
> +++ b/arch/powerpc/kernel/Makefile
> @@ -44,16 +44,25 @@ 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 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 \
> +ifndef CONFIG_PPC64
> +obj-y += signal_32.o
> +else
> +ifdef CONFIG_COMPAT
> +obj-y += signal_32.o
> +endif
> +endif
> +obj-$(CONFIG_PPC64) += setup_64.o signal_64.o \
> paca.o nvram_64.o firmware.o \
> syscall_64.o

That's still a bit messy. You could have:

obj-y = +=signal_$(BITS).o
obj-$(CONFIG_COMPAT) += signal_32.o

> +ifdef CONFIG_COMPAT
> +obj-$(CONFIG_PPC64) += sys_ppc32.o ptrace32.o
> +endif

AFAIK, CONFIG_COMPAT is only defined when CONFIG_PP64 is defined, so
could be:

obj-$(CONFIG_COMPAT) += sys_ppc32.o ptrace32.o

And could be grouped with the above 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

Can we avoid this ifdef ?

>
> /* 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..ffd045e9fb57 100644
> --- a/arch/powerpc/kernel/signal.c
> +++ b/arch/powerpc/kernel/signal.c
> @@ -277,14 +277,15 @@ static void do_signal(struct task_struct *tsk)
>
> rseq_signal_deliver(&ksig, tsk->thread.regs);
>
> +#if !defined(CONFIG_PPC64) || defined(CONFIG_COMPAT)
> if (is32) {
> if (ksig.ka.sa.sa_flags & SA_SIGINFO)
> ret = handle_rt_signal32(&ksig, oldset, tsk);
> else
> ret = handle_signal32(&ksig, oldset, tsk);
> - } else {
> + } else

" if only one branch of a conditional statement is a single statement
[...] use braces in both branches"

Ref
https://www.kernel.org/doc/html/latest/process/coding-style.html#placing-braces-and-spaces

> +#endif /* 32bit */

Having an #ifdef in a middle of a if/else is gross.

Check what are the possible values for is32. It will be always true
which CONFIG_PPC32.
If you can make sure it is always false without CONFIG_COMPAT, you are
done. If not, then combine the if(is32) with something involving
IS_ENABLED(CONFIG_COMPAT).

> ret = handle_rt_signal64(&ksig, oldset, tsk);
> - }
>
> tsk->thread.regs->trap = 0;
> signal_setup_done(ret, &ksig, test_thread_flag(TIF_SINGLESTEP));
> diff --git a/arch/powerpc/kernel/syscall_64.c b/arch/powerpc/kernel/syscall_64.c
> index 98ed970796d5..3f48262b512d 100644
> --- a/arch/powerpc/kernel/syscall_64.c
> +++ b/arch/powerpc/kernel/syscall_64.c
> @@ -100,6 +100,7 @@ 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();
>
> +#ifdef CONFIG_COMPAT
> if (unlikely(ti_flags & _TIF_32BIT)) {
> f = (void *)compat_sys_call_table[r0];

Don't opt out compat_sys_call_table[] declaration in .h file, and use:

if (IS_ENABLED(CONFIG_COMPAT) && unlikely(ti_flags & _TIF_32BIT)) {

>
> @@ -110,9 +111,9 @@ long system_call_exception(long r3, long r4, long r5, long r6, long r7, long r8,
> r7 &= 0x00000000ffffffffULL;
> r8 &= 0x00000000ffffffffULL;
>
> - } else {
> + } else
> +#endif /* CONFIG_COMPAT */

Same comment above braces and #ifdefs in the middle of an if/else

> f = (void *)sys_call_table[r0];
> - }
>
> return f(r3, r4, r5, r6, r7, r8);
> }
> diff --git a/arch/powerpc/kernel/vdso.c b/arch/powerpc/kernel/vdso.c
> index d60598113a9f..a991b5d69010 100644
> --- a/arch/powerpc/kernel/vdso.c
> +++ b/arch/powerpc/kernel/vdso.c
> @@ -667,7 +667,7 @@ static void __init vdso_setup_syscall_map(void)
> {
> unsigned int i;
> extern unsigned long *sys_call_table;
> -#ifdef CONFIG_PPC64
> +#ifdef CONFIG_COMPAT

It should be possible to get rid of that #ifdef completely.

> extern unsigned long *compat_sys_call_table;
> #endif
> extern unsigned long sys_ni_syscall;
> @@ -678,9 +678,11 @@ 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);
> +#ifdef CONFIG_COMPAT

Use if (IS_ENABLED(CONFIG_COMPAT && compat_sys_call_table[i] !=
sys_ni_syscall)

> if (compat_sys_call_table[i] != sys_ni_syscall)
> vdso_data->syscall_map_32[i >> 5] |=
> 0x80000000UL >> (i & 0x1f);
> +#endif /* CONFIG_COMPAT */
> #else /* CONFIG_PPC64 */
> if (sys_call_table[i] != sys_ni_syscall)
> vdso_data->syscall_map_32[i >> 5] |=
> diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
> index c84bbd4298a0..b3dacc8bc98d 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
> #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);
> }
>
> +#ifdef CONFIG_COMPAT

Unneeded #ifdef

> static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
> {
> if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
> @@ -180,6 +181,7 @@ static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
>
> return read_user_stack_slow(ptr, ret, 4);
> }
> +#endif
>
> static inline int valid_user_sp(unsigned long sp, int is_64)
> {
> @@ -341,6 +343,7 @@ static inline int valid_user_sp(unsigned long sp, int is_64)
>
> #endif /* CONFIG_PPC64 */
>
> +#if !defined(CONFIG_PPC64) || defined(CONFIG_COMPAT)

You don't need to opt that out.

> /*
> * Layout for non-RT signal frames
> */
> @@ -482,12 +485,15 @@ 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_PPC64) || defined(CONFIG_COMPAT)
> + if (!current_is_64bit())
> perf_callchain_user_32(entry, regs);
> + else
> +#endif
> + perf_callchain_user_64(entry, regs);

Please rewrite using IS_ENABLED() instead of #ifdefs.

Christophe