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SubjectRe: [PATCH v5 3/5] powerpc/64: make buildable without CONFIG_COMPAT
On Fri, 30 Aug 2019 06:35:13 +0000 (UTC)
Christophe Leroy <christophe.leroy@c-s.fr> 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 <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
> > 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;
> }
>
> 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.

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 */
>

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