by Christophe Leroy

[permalink] [raw]

Subject: Re: [PATCH v5 3/5] powerpc/64: make buildable without CONFIG_COMPAT

Le 30/08/2019 à 09:54, Michal Suchánek a écrit :
> On Fri, 30 Aug 2019 06:35:13 +0000 (UTC)
> Christophe Leroy <[email protected]> wrote:
>
>> On 08/29/2019 10:28 PM, Michal Suchanek wrote:
>>> There are numerous references to 32bit functions in generic and 64bit
>>> code so ifdef them out.
>>>
>>> Signed-off-by: Michal Suchanek <[email protected]>
>>> ---
>>> 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
>>> v5:
>>> - avoid unreachable code on 32bit
>>> - make is_current_64bit constant on !COMPAT
>>> - add stub perf_callchain_user_32 to avoid some ifdefs
>>> ---
>>> 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 | 13 +++++++++++--
>>> 7 files changed, 23 insertions(+), 17 deletions(-)
>>>
>> [...]
>>
>>> diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
>>> index c84bbd4298a0..881be5c4e9bb 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>
>>> @@ -291,7 +291,8 @@ static inline int current_is_64bit(void)
>>> * interrupt stack, and the thread flags don't get copied over
>>> * from the thread_info on the main stack to the interrupt stack.
>>> */
>>> - return !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
>>> + return !IS_ENABLED(CONFIG_COMPAT) ||
>>> + !test_ti_thread_flag(task_thread_info(current), TIF_32BIT);
>>> }
>>>
>>> #else /* CONFIG_PPC64 */
>>> @@ -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
>>> */
>>> @@ -482,6 +484,13 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
>>> sp = next_sp;
>>> }
>>> }
>>> +#else /* 32bit */
>>> +static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
>>> + struct pt_regs *regs)
>>> +{
>>> + (void)&read_user_stack_32; /* unused if !COMPAT */
>>
>> That looks pretty much like a hack.
>>
>> See possible alternative below.
>>
>>> +}
>>> +#endif /* 32bit */
>>>
>>> void
>>> perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs)
>>>
>>
>> ---
>> arch/powerpc/perf/callchain.c | 62 +++++++++++++++++++------------------------
>> 1 file changed, 27 insertions(+), 35 deletions(-)
>>
>> diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
>> index 881be5c4e9bb..1b169b32776a 100644
>> --- a/arch/powerpc/perf/callchain.c
>> +++ b/arch/powerpc/perf/callchain.c
>> @@ -165,22 +165,6 @@ static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
>> return read_user_stack_slow(ptr, ret, 8);
>> }
>>
>> -static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
>> -{
>> - if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
>> - ((unsigned long)ptr & 3))
>> - return -EFAULT;
>> -
>> - pagefault_disable();
>> - if (!__get_user_inatomic(*ret, ptr)) {
>> - pagefault_enable();
>> - return 0;
>> - }
>> - pagefault_enable();
>> -
>> - return read_user_stack_slow(ptr, ret, 4);
>> -}
>> -
>> static inline int valid_user_sp(unsigned long sp, int is_64)
>> {
>> if (!sp || (sp & 7) || sp > (is_64 ? TASK_SIZE : 0x100000000UL) - 32)
>> @@ -296,25 +280,10 @@ static inline int current_is_64bit(void)
>> }
>>
>> #else /* CONFIG_PPC64 */
>> -/*
>> - * On 32-bit we just access the address and let hash_page create a
>> - * HPTE if necessary, so there is no need to fall back to reading
>> - * the page tables. Since this is called at interrupt level,
>> - * do_page_fault() won't treat a DSI as a page fault.
>> - */
>> -static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
>> -{
>> - int rc;
>> -
>> - if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
>> - ((unsigned long)ptr & 3))
>> - return -EFAULT;
>>
>> - pagefault_disable();
>> - rc = __get_user_inatomic(*ret, ptr);
>> - pagefault_enable();
>> -
>> - return rc;
>> +static int read_user_stack_slow(void __user *ptr, void *buf, int nb)
>> +{
>> + return 0;

Here it is

>> }
>>
>> static inline void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
>> @@ -344,6 +313,30 @@ static inline int valid_user_sp(unsigned long sp, int is_64)
>>
>> #if defined(CONFIG_PPC32) || defined(CONFIG_COMPAT)
>> /*
>> + * On 32-bit we just access the address and let hash_page create a
>> + * HPTE if necessary, so there is no need to fall back to reading
>> + * the page tables. Since this is called at interrupt level,
>> + * do_page_fault() won't treat a DSI as a page fault.
>> + */
>> +static int read_user_stack_32(unsigned int __user *ptr, unsigned int *ret)
>> +{
>> + int rc;
>> +
>> + if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned int) ||
>> + ((unsigned long)ptr & 3))
>> + return -EFAULT;
>> +
>> + pagefault_disable();
>> + rc = __get_user_inatomic(*ret, ptr);
>> + pagefault_enable();
>> +
>> + if (IS_ENABLED(CONFIG_PPC32) || !rc)
>> + return rc;
>> +
>> + return read_user_stack_slow(ptr, ret, 4);
> Which is not declared here. This is not intended to be the final state,
> anyway.

Yes it is declared here, see above

Christophe

>
> Thanks
>
> Michal
>> +}
>> +
>> +/*
>> * Layout for non-RT signal frames
>> */
>> struct signal_frame_32 {
>> @@ -488,7 +481,6 @@ static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
>> static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
>> struct pt_regs *regs)
>> {
>> - (void)&read_user_stack_32; /* unused if !COMPAT */
>> }
>> #endif /* 32bit */
>>