On Fri, 30 Aug 2019 23:03:43 +0200
Michal Suchanek <msucha...@suse.de> wrote:

> Building callchain.c with !COMPAT proved quite ugly with all the
> defines. Splitting out the 32bit and 64bit parts looks better.
> 
> No code change intended.

valid_user_sp is broken in compat. It needs to be ifdefed for the 32bit
case.
> 
> Signed-off-by: Michal Suchanek <msucha...@suse.de>
> Reviewed-by: Christophe Leroy <christophe.le...@c-s.fr>
> ---
> v6:
>  - move current_is_64bit consolidetaion to earlier patch
>  - move defines to the top of callchain_32.c
>  - Makefile cleanup
> ---
>  arch/powerpc/perf/Makefile       |   5 +-
>  arch/powerpc/perf/callchain.c    | 365 +------------------------------
>  arch/powerpc/perf/callchain.h    |  11 +
>  arch/powerpc/perf/callchain_32.c | 204 +++++++++++++++++
>  arch/powerpc/perf/callchain_64.c | 185 ++++++++++++++++
>  5 files changed, 405 insertions(+), 365 deletions(-)
>  create mode 100644 arch/powerpc/perf/callchain.h
>  create mode 100644 arch/powerpc/perf/callchain_32.c
>  create mode 100644 arch/powerpc/perf/callchain_64.c
> 
> diff --git a/arch/powerpc/perf/Makefile b/arch/powerpc/perf/Makefile
> index c155dcbb8691..53d614e98537 100644
> --- a/arch/powerpc/perf/Makefile
> +++ b/arch/powerpc/perf/Makefile
> @@ -1,6 +1,9 @@
>  # SPDX-License-Identifier: GPL-2.0
>  
> -obj-$(CONFIG_PERF_EVENTS)    += callchain.o perf_regs.o
> +obj-$(CONFIG_PERF_EVENTS)    += callchain.o callchain_$(BITS).o perf_regs.o
> +ifdef CONFIG_COMPAT
> +obj-$(CONFIG_PERF_EVENTS)    += callchain_32.o
> +endif
>  
>  obj-$(CONFIG_PPC_PERF_CTRS)  += core-book3s.o bhrb.o
>  obj64-$(CONFIG_PPC_PERF_CTRS)        += ppc970-pmu.o power5-pmu.o \
> diff --git a/arch/powerpc/perf/callchain.c b/arch/powerpc/perf/callchain.c
> index 9b8dc822f531..8f30f1b47c78 100644
> --- a/arch/powerpc/perf/callchain.c
> +++ b/arch/powerpc/perf/callchain.c
> @@ -15,11 +15,9 @@
>  #include <asm/sigcontext.h>
>  #include <asm/ucontext.h>
>  #include <asm/vdso.h>
> -#ifdef CONFIG_COMPAT
> -#include "../kernel/ppc32.h"
> -#endif
>  #include <asm/pte-walk.h>
>  
> +#include "callchain.h"
>  
>  /*
>   * Is sp valid as the address of the next kernel stack frame after prev_sp?
> @@ -102,367 +100,6 @@ perf_callchain_kernel(struct perf_callchain_entry_ctx 
> *entry, struct pt_regs *re
>       }
>  }
>  
> -#ifdef CONFIG_PPC64
> -/*
> - * On 64-bit we don't want to invoke hash_page on user addresses from
> - * interrupt context, so if the access faults, we read the page tables
> - * to find which page (if any) is mapped and access it directly.
> - */
> -static int read_user_stack_slow(void __user *ptr, void *buf, int nb)
> -{
> -     int ret = -EFAULT;
> -     pgd_t *pgdir;
> -     pte_t *ptep, pte;
> -     unsigned shift;
> -     unsigned long addr = (unsigned long) ptr;
> -     unsigned long offset;
> -     unsigned long pfn, flags;
> -     void *kaddr;
> -
> -     pgdir = current->mm->pgd;
> -     if (!pgdir)
> -             return -EFAULT;
> -
> -     local_irq_save(flags);
> -     ptep = find_current_mm_pte(pgdir, addr, NULL, &shift);
> -     if (!ptep)
> -             goto err_out;
> -     if (!shift)
> -             shift = PAGE_SHIFT;
> -
> -     /* align address to page boundary */
> -     offset = addr & ((1UL << shift) - 1);
> -
> -     pte = READ_ONCE(*ptep);
> -     if (!pte_present(pte) || !pte_user(pte))
> -             goto err_out;
> -     pfn = pte_pfn(pte);
> -     if (!page_is_ram(pfn))
> -             goto err_out;
> -
> -     /* no highmem to worry about here */
> -     kaddr = pfn_to_kaddr(pfn);
> -     memcpy(buf, kaddr + offset, nb);
> -     ret = 0;
> -err_out:
> -     local_irq_restore(flags);
> -     return ret;
> -}
> -
> -static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
> -{
> -     if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
> -         ((unsigned long)ptr & 7))
> -             return -EFAULT;
> -
> -     pagefault_disable();
> -     if (!__get_user_inatomic(*ret, ptr)) {
> -             pagefault_enable();
> -             return 0;
> -     }
> -     pagefault_enable();
> -
> -     return read_user_stack_slow(ptr, ret, 8);
> -}
> -
> -static inline int valid_user_sp(unsigned long sp, int is_64)
> -{
> -     if (!sp || (sp & 7) || sp > (is_64 ? TASK_SIZE : 0x100000000UL) - 32)
> -             return 0;
> -     return 1;
> -}
> -
> -/*
> - * 64-bit user processes use the same stack frame for RT and non-RT signals.
> - */
> -struct signal_frame_64 {
> -     char            dummy[__SIGNAL_FRAMESIZE];
> -     struct ucontext uc;
> -     unsigned long   unused[2];
> -     unsigned int    tramp[6];
> -     struct siginfo  *pinfo;
> -     void            *puc;
> -     struct siginfo  info;
> -     char            abigap[288];
> -};
> -
> -static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
> -{
> -     if (nip == fp + offsetof(struct signal_frame_64, tramp))
> -             return 1;
> -     if (vdso64_rt_sigtramp && current->mm->context.vdso_base &&
> -         nip == current->mm->context.vdso_base + vdso64_rt_sigtramp)
> -             return 1;
> -     return 0;
> -}
> -
> -/*
> - * Do some sanity checking on the signal frame pointed to by sp.
> - * We check the pinfo and puc pointers in the frame.
> - */
> -static int sane_signal_64_frame(unsigned long sp)
> -{
> -     struct signal_frame_64 __user *sf;
> -     unsigned long pinfo, puc;
> -
> -     sf = (struct signal_frame_64 __user *) sp;
> -     if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
> -         read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
> -             return 0;
> -     return pinfo == (unsigned long) &sf->info &&
> -             puc == (unsigned long) &sf->uc;
> -}
> -
> -static void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
> -                                struct pt_regs *regs)
> -{
> -     unsigned long sp, next_sp;
> -     unsigned long next_ip;
> -     unsigned long lr;
> -     long level = 0;
> -     struct signal_frame_64 __user *sigframe;
> -     unsigned long __user *fp, *uregs;
> -
> -     next_ip = perf_instruction_pointer(regs);
> -     lr = regs->link;
> -     sp = regs->gpr[1];
> -     perf_callchain_store(entry, next_ip);
> -
> -     while (entry->nr < entry->max_stack) {
> -             fp = (unsigned long __user *) sp;
> -             if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
> -                     return;
> -             if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
> -                     return;
> -
> -             /*
> -              * Note: the next_sp - sp >= signal frame size check
> -              * is true when next_sp < sp, which can happen when
> -              * transitioning from an alternate signal stack to the
> -              * normal stack.
> -              */
> -             if (next_sp - sp >= sizeof(struct signal_frame_64) &&
> -                 (is_sigreturn_64_address(next_ip, sp) ||
> -                  (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
> -                 sane_signal_64_frame(sp)) {
> -                     /*
> -                      * This looks like an signal frame
> -                      */
> -                     sigframe = (struct signal_frame_64 __user *) sp;
> -                     uregs = sigframe->uc.uc_mcontext.gp_regs;
> -                     if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
> -                         read_user_stack_64(&uregs[PT_LNK], &lr) ||
> -                         read_user_stack_64(&uregs[PT_R1], &sp))
> -                             return;
> -                     level = 0;
> -                     perf_callchain_store_context(entry, PERF_CONTEXT_USER);
> -                     perf_callchain_store(entry, next_ip);
> -                     continue;
> -             }
> -
> -             if (level == 0)
> -                     next_ip = lr;
> -             perf_callchain_store(entry, next_ip);
> -             ++level;
> -             sp = next_sp;
> -     }
> -}
> -
> -#else  /* CONFIG_PPC64 */
> -static int read_user_stack_slow(void __user *ptr, void *buf, int nb)
> -{
> -     return 0;
> -}
> -#endif /* 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();
> -
> -     if (IS_ENABLED(CONFIG_PPC64) && rc)
> -             return read_user_stack_slow(ptr, ret, 4);
> -     return rc;
> -}
> -
> -#ifndef CONFIG_PPC64
> -static inline void perf_callchain_user_64(struct perf_callchain_entry_ctx 
> *entry,
> -                                       struct pt_regs *regs)
> -{
> -}
> -
> -static inline int valid_user_sp(unsigned long sp, int is_64)
> -{
> -     if (!sp || (sp & 7) || sp > TASK_SIZE - 32)
> -             return 0;
> -     return 1;
> -}
> -
> -#define __SIGNAL_FRAMESIZE32 __SIGNAL_FRAMESIZE
> -#define sigcontext32         sigcontext
> -#define mcontext32           mcontext
> -#define ucontext32           ucontext
> -#define compat_siginfo_t     struct siginfo
> -
> -#endif /* CONFIG_PPC64 */
> -
> -#if defined(CONFIG_PPC32) || defined(CONFIG_COMPAT)
> -/*
> - * Layout for non-RT signal frames
> - */
> -struct signal_frame_32 {
> -     char                    dummy[__SIGNAL_FRAMESIZE32];
> -     struct sigcontext32     sctx;
> -     struct mcontext32       mctx;
> -     int                     abigap[56];
> -};
> -
> -/*
> - * Layout for RT signal frames
> - */
> -struct rt_signal_frame_32 {
> -     char                    dummy[__SIGNAL_FRAMESIZE32 + 16];
> -     compat_siginfo_t        info;
> -     struct ucontext32       uc;
> -     int                     abigap[56];
> -};
> -
> -static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
> -{
> -     if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
> -             return 1;
> -     if (vdso32_sigtramp && current->mm->context.vdso_base &&
> -         nip == current->mm->context.vdso_base + vdso32_sigtramp)
> -             return 1;
> -     return 0;
> -}
> -
> -static int is_rt_sigreturn_32_address(unsigned int nip, unsigned int fp)
> -{
> -     if (nip == fp + offsetof(struct rt_signal_frame_32,
> -                              uc.uc_mcontext.mc_pad))
> -             return 1;
> -     if (vdso32_rt_sigtramp && current->mm->context.vdso_base &&
> -         nip == current->mm->context.vdso_base + vdso32_rt_sigtramp)
> -             return 1;
> -     return 0;
> -}
> -
> -static int sane_signal_32_frame(unsigned int sp)
> -{
> -     struct signal_frame_32 __user *sf;
> -     unsigned int regs;
> -
> -     sf = (struct signal_frame_32 __user *) (unsigned long) sp;
> -     if (read_user_stack_32((unsigned int __user *) &sf->sctx.regs, &regs))
> -             return 0;
> -     return regs == (unsigned long) &sf->mctx;
> -}
> -
> -static int sane_rt_signal_32_frame(unsigned int sp)
> -{
> -     struct rt_signal_frame_32 __user *sf;
> -     unsigned int regs;
> -
> -     sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
> -     if (read_user_stack_32((unsigned int __user *) &sf->uc.uc_regs, &regs))
> -             return 0;
> -     return regs == (unsigned long) &sf->uc.uc_mcontext;
> -}
> -
> -static unsigned int __user *signal_frame_32_regs(unsigned int sp,
> -                             unsigned int next_sp, unsigned int next_ip)
> -{
> -     struct mcontext32 __user *mctx = NULL;
> -     struct signal_frame_32 __user *sf;
> -     struct rt_signal_frame_32 __user *rt_sf;
> -
> -     /*
> -      * Note: the next_sp - sp >= signal frame size check
> -      * is true when next_sp < sp, for example, when
> -      * transitioning from an alternate signal stack to the
> -      * normal stack.
> -      */
> -     if (next_sp - sp >= sizeof(struct signal_frame_32) &&
> -         is_sigreturn_32_address(next_ip, sp) &&
> -         sane_signal_32_frame(sp)) {
> -             sf = (struct signal_frame_32 __user *) (unsigned long) sp;
> -             mctx = &sf->mctx;
> -     }
> -
> -     if (!mctx && next_sp - sp >= sizeof(struct rt_signal_frame_32) &&
> -         is_rt_sigreturn_32_address(next_ip, sp) &&
> -         sane_rt_signal_32_frame(sp)) {
> -             rt_sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
> -             mctx = &rt_sf->uc.uc_mcontext;
> -     }
> -
> -     if (!mctx)
> -             return NULL;
> -     return mctx->mc_gregs;
> -}
> -
> -static void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
> -                                struct pt_regs *regs)
> -{
> -     unsigned int sp, next_sp;
> -     unsigned int next_ip;
> -     unsigned int lr;
> -     long level = 0;
> -     unsigned int __user *fp, *uregs;
> -
> -     next_ip = perf_instruction_pointer(regs);
> -     lr = regs->link;
> -     sp = regs->gpr[1];
> -     perf_callchain_store(entry, next_ip);
> -
> -     while (entry->nr < entry->max_stack) {
> -             fp = (unsigned int __user *) (unsigned long) sp;
> -             if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
> -                     return;
> -             if (level > 0 && read_user_stack_32(&fp[1], &next_ip))
> -                     return;
> -
> -             uregs = signal_frame_32_regs(sp, next_sp, next_ip);
> -             if (!uregs && level <= 1)
> -                     uregs = signal_frame_32_regs(sp, next_sp, lr);
> -             if (uregs) {
> -                     /*
> -                      * This looks like an signal frame, so restart
> -                      * the stack trace with the values in it.
> -                      */
> -                     if (read_user_stack_32(&uregs[PT_NIP], &next_ip) ||
> -                         read_user_stack_32(&uregs[PT_LNK], &lr) ||
> -                         read_user_stack_32(&uregs[PT_R1], &sp))
> -                             return;
> -                     level = 0;
> -                     perf_callchain_store_context(entry, PERF_CONTEXT_USER);
> -                     perf_callchain_store(entry, next_ip);
> -                     continue;
> -             }
> -
> -             if (level == 0)
> -                     next_ip = lr;
> -             perf_callchain_store(entry, next_ip);
> -             ++level;
> -             sp = next_sp;
> -     }
> -}
> -#endif /* 32bit */
> -
>  static inline int current_is_64bit(void)
>  {
>       if (!IS_ENABLED(CONFIG_COMPAT))
> diff --git a/arch/powerpc/perf/callchain.h b/arch/powerpc/perf/callchain.h
> new file mode 100644
> index 000000000000..63ffb43f3668
> --- /dev/null
> +++ b/arch/powerpc/perf/callchain.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#ifndef _POWERPC_PERF_CALLCHAIN_H
> +#define _POWERPC_PERF_CALLCHAIN_H
> +
> +int read_user_stack_slow(void __user *ptr, void *buf, int nb);
> +void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
> +                         struct pt_regs *regs);
> +void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
> +                         struct pt_regs *regs);
> +
> +#endif /* _POWERPC_PERF_CALLCHAIN_H */
> diff --git a/arch/powerpc/perf/callchain_32.c 
> b/arch/powerpc/perf/callchain_32.c
> new file mode 100644
> index 000000000000..01a38d929078
> --- /dev/null
> +++ b/arch/powerpc/perf/callchain_32.c
> @@ -0,0 +1,204 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Performance counter callchain support - powerpc architecture code
> + *
> + * Copyright © 2009 Paul Mackerras, IBM Corporation.
> + */
> +#include <linux/kernel.h>
> +#include <linux/sched.h>
> +#include <linux/perf_event.h>
> +#include <linux/percpu.h>
> +#include <linux/uaccess.h>
> +#include <linux/mm.h>
> +#include <asm/ptrace.h>
> +#include <asm/pgtable.h>
> +#include <asm/sigcontext.h>
> +#include <asm/ucontext.h>
> +#include <asm/vdso.h>
> +#include <asm/pte-walk.h>
> +
> +#include "callchain.h"
> +
> +#ifdef CONFIG_PPC64
> +#include "../kernel/ppc32.h"
> +#else  /* CONFIG_PPC64 */
> +
> +#define __SIGNAL_FRAMESIZE32 __SIGNAL_FRAMESIZE
> +#define sigcontext32         sigcontext
> +#define mcontext32           mcontext
> +#define ucontext32           ucontext
> +#define compat_siginfo_t     struct siginfo
> +
> +#endif /* 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();
> +
> +     if (IS_ENABLED(CONFIG_PPC64) && rc)
> +             return read_user_stack_slow(ptr, ret, 4);
> +     return rc;
> +}
> +
> +static inline int valid_user_sp(unsigned long sp, int is_64)
> +{
> +     if (!sp || (sp & 7) || sp > TASK_SIZE - 32)
> +             return 0;
> +     return 1;
> +}
> +
> +/*
> + * Layout for non-RT signal frames
> + */
> +struct signal_frame_32 {
> +     char                    dummy[__SIGNAL_FRAMESIZE32];
> +     struct sigcontext32     sctx;
> +     struct mcontext32       mctx;
> +     int                     abigap[56];
> +};
> +
> +/*
> + * Layout for RT signal frames
> + */
> +struct rt_signal_frame_32 {
> +     char                    dummy[__SIGNAL_FRAMESIZE32 + 16];
> +     compat_siginfo_t        info;
> +     struct ucontext32       uc;
> +     int                     abigap[56];
> +};
> +
> +static int is_sigreturn_32_address(unsigned int nip, unsigned int fp)
> +{
> +     if (nip == fp + offsetof(struct signal_frame_32, mctx.mc_pad))
> +             return 1;
> +     if (vdso32_sigtramp && current->mm->context.vdso_base &&
> +         nip == current->mm->context.vdso_base + vdso32_sigtramp)
> +             return 1;
> +     return 0;
> +}
> +
> +static int is_rt_sigreturn_32_address(unsigned int nip, unsigned int fp)
> +{
> +     if (nip == fp + offsetof(struct rt_signal_frame_32,
> +                              uc.uc_mcontext.mc_pad))
> +             return 1;
> +     if (vdso32_rt_sigtramp && current->mm->context.vdso_base &&
> +         nip == current->mm->context.vdso_base + vdso32_rt_sigtramp)
> +             return 1;
> +     return 0;
> +}
> +
> +static int sane_signal_32_frame(unsigned int sp)
> +{
> +     struct signal_frame_32 __user *sf;
> +     unsigned int regs;
> +
> +     sf = (struct signal_frame_32 __user *) (unsigned long) sp;
> +     if (read_user_stack_32((unsigned int __user *) &sf->sctx.regs, &regs))
> +             return 0;
> +     return regs == (unsigned long) &sf->mctx;
> +}
> +
> +static int sane_rt_signal_32_frame(unsigned int sp)
> +{
> +     struct rt_signal_frame_32 __user *sf;
> +     unsigned int regs;
> +
> +     sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
> +     if (read_user_stack_32((unsigned int __user *) &sf->uc.uc_regs, &regs))
> +             return 0;
> +     return regs == (unsigned long) &sf->uc.uc_mcontext;
> +}
> +
> +static unsigned int __user *signal_frame_32_regs(unsigned int sp,
> +                             unsigned int next_sp, unsigned int next_ip)
> +{
> +     struct mcontext32 __user *mctx = NULL;
> +     struct signal_frame_32 __user *sf;
> +     struct rt_signal_frame_32 __user *rt_sf;
> +
> +     /*
> +      * Note: the next_sp - sp >= signal frame size check
> +      * is true when next_sp < sp, for example, when
> +      * transitioning from an alternate signal stack to the
> +      * normal stack.
> +      */
> +     if (next_sp - sp >= sizeof(struct signal_frame_32) &&
> +         is_sigreturn_32_address(next_ip, sp) &&
> +         sane_signal_32_frame(sp)) {
> +             sf = (struct signal_frame_32 __user *) (unsigned long) sp;
> +             mctx = &sf->mctx;
> +     }
> +
> +     if (!mctx && next_sp - sp >= sizeof(struct rt_signal_frame_32) &&
> +         is_rt_sigreturn_32_address(next_ip, sp) &&
> +         sane_rt_signal_32_frame(sp)) {
> +             rt_sf = (struct rt_signal_frame_32 __user *) (unsigned long) sp;
> +             mctx = &rt_sf->uc.uc_mcontext;
> +     }
> +
> +     if (!mctx)
> +             return NULL;
> +     return mctx->mc_gregs;
> +}
> +
> +void perf_callchain_user_32(struct perf_callchain_entry_ctx *entry,
> +                         struct pt_regs *regs)
> +{
> +     unsigned int sp, next_sp;
> +     unsigned int next_ip;
> +     unsigned int lr;
> +     long level = 0;
> +     unsigned int __user *fp, *uregs;
> +
> +     next_ip = perf_instruction_pointer(regs);
> +     lr = regs->link;
> +     sp = regs->gpr[1];
> +     perf_callchain_store(entry, next_ip);
> +
> +     while (entry->nr < entry->max_stack) {
> +             fp = (unsigned int __user *) (unsigned long) sp;
> +             if (!valid_user_sp(sp, 0) || read_user_stack_32(fp, &next_sp))
> +                     return;
> +             if (level > 0 && read_user_stack_32(&fp[1], &next_ip))
> +                     return;
> +
> +             uregs = signal_frame_32_regs(sp, next_sp, next_ip);
> +             if (!uregs && level <= 1)
> +                     uregs = signal_frame_32_regs(sp, next_sp, lr);
> +             if (uregs) {
> +                     /*
> +                      * This looks like an signal frame, so restart
> +                      * the stack trace with the values in it.
> +                      */
> +                     if (read_user_stack_32(&uregs[PT_NIP], &next_ip) ||
> +                         read_user_stack_32(&uregs[PT_LNK], &lr) ||
> +                         read_user_stack_32(&uregs[PT_R1], &sp))
> +                             return;
> +                     level = 0;
> +                     perf_callchain_store_context(entry, PERF_CONTEXT_USER);
> +                     perf_callchain_store(entry, next_ip);
> +                     continue;
> +             }
> +
> +             if (level == 0)
> +                     next_ip = lr;
> +             perf_callchain_store(entry, next_ip);
> +             ++level;
> +             sp = next_sp;
> +     }
> +}
> diff --git a/arch/powerpc/perf/callchain_64.c 
> b/arch/powerpc/perf/callchain_64.c
> new file mode 100644
> index 000000000000..60308c2221a8
> --- /dev/null
> +++ b/arch/powerpc/perf/callchain_64.c
> @@ -0,0 +1,185 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Performance counter callchain support - powerpc architecture code
> + *
> + * Copyright © 2009 Paul Mackerras, IBM Corporation.
> + */
> +#include <linux/kernel.h>
> +#include <linux/sched.h>
> +#include <linux/perf_event.h>
> +#include <linux/percpu.h>
> +#include <linux/uaccess.h>
> +#include <linux/mm.h>
> +#include <asm/ptrace.h>
> +#include <asm/pgtable.h>
> +#include <asm/sigcontext.h>
> +#include <asm/ucontext.h>
> +#include <asm/vdso.h>
> +#include <asm/pte-walk.h>
> +
> +#include "callchain.h"
> +
> +/*
> + * On 64-bit we don't want to invoke hash_page on user addresses from
> + * interrupt context, so if the access faults, we read the page tables
> + * to find which page (if any) is mapped and access it directly.
> + */
> +int read_user_stack_slow(void __user *ptr, void *buf, int nb)
> +{
> +     int ret = -EFAULT;
> +     pgd_t *pgdir;
> +     pte_t *ptep, pte;
> +     unsigned int shift;
> +     unsigned long addr = (unsigned long) ptr;
> +     unsigned long offset;
> +     unsigned long pfn, flags;
> +     void *kaddr;
> +
> +     pgdir = current->mm->pgd;
> +     if (!pgdir)
> +             return -EFAULT;
> +
> +     local_irq_save(flags);
> +     ptep = find_current_mm_pte(pgdir, addr, NULL, &shift);
> +     if (!ptep)
> +             goto err_out;
> +     if (!shift)
> +             shift = PAGE_SHIFT;
> +
> +     /* align address to page boundary */
> +     offset = addr & ((1UL << shift) - 1);
> +
> +     pte = READ_ONCE(*ptep);
> +     if (!pte_present(pte) || !pte_user(pte))
> +             goto err_out;
> +     pfn = pte_pfn(pte);
> +     if (!page_is_ram(pfn))
> +             goto err_out;
> +
> +     /* no highmem to worry about here */
> +     kaddr = pfn_to_kaddr(pfn);
> +     memcpy(buf, kaddr + offset, nb);
> +     ret = 0;
> +err_out:
> +     local_irq_restore(flags);
> +     return ret;
> +}
> +
> +static int read_user_stack_64(unsigned long __user *ptr, unsigned long *ret)
> +{
> +     if ((unsigned long)ptr > TASK_SIZE - sizeof(unsigned long) ||
> +         ((unsigned long)ptr & 7))
> +             return -EFAULT;
> +
> +     pagefault_disable();
> +     if (!__get_user_inatomic(*ret, ptr)) {
> +             pagefault_enable();
> +             return 0;
> +     }
> +     pagefault_enable();
> +
> +     return read_user_stack_slow(ptr, ret, 8);
> +}
> +
> +static inline int valid_user_sp(unsigned long sp, int is_64)
> +{
> +     if (!sp || (sp & 7) || sp > (is_64 ? TASK_SIZE : 0x100000000UL) - 32)
> +             return 0;
> +     return 1;
> +}
> +
> +/*
> + * 64-bit user processes use the same stack frame for RT and non-RT signals.
> + */
> +struct signal_frame_64 {
> +     char            dummy[__SIGNAL_FRAMESIZE];
> +     struct ucontext uc;
> +     unsigned long   unused[2];
> +     unsigned int    tramp[6];
> +     struct siginfo  *pinfo;
> +     void            *puc;
> +     struct siginfo  info;
> +     char            abigap[288];
> +};
> +
> +static int is_sigreturn_64_address(unsigned long nip, unsigned long fp)
> +{
> +     if (nip == fp + offsetof(struct signal_frame_64, tramp))
> +             return 1;
> +     if (vdso64_rt_sigtramp && current->mm->context.vdso_base &&
> +         nip == current->mm->context.vdso_base + vdso64_rt_sigtramp)
> +             return 1;
> +     return 0;
> +}
> +
> +/*
> + * Do some sanity checking on the signal frame pointed to by sp.
> + * We check the pinfo and puc pointers in the frame.
> + */
> +static int sane_signal_64_frame(unsigned long sp)
> +{
> +     struct signal_frame_64 __user *sf;
> +     unsigned long pinfo, puc;
> +
> +     sf = (struct signal_frame_64 __user *) sp;
> +     if (read_user_stack_64((unsigned long __user *) &sf->pinfo, &pinfo) ||
> +         read_user_stack_64((unsigned long __user *) &sf->puc, &puc))
> +             return 0;
> +     return pinfo == (unsigned long) &sf->info &&
> +             puc == (unsigned long) &sf->uc;
> +}
> +
> +void perf_callchain_user_64(struct perf_callchain_entry_ctx *entry,
> +                         struct pt_regs *regs)
> +{
> +     unsigned long sp, next_sp;
> +     unsigned long next_ip;
> +     unsigned long lr;
> +     long level = 0;
> +     struct signal_frame_64 __user *sigframe;
> +     unsigned long __user *fp, *uregs;
> +
> +     next_ip = perf_instruction_pointer(regs);
> +     lr = regs->link;
> +     sp = regs->gpr[1];
> +     perf_callchain_store(entry, next_ip);
> +
> +     while (entry->nr < entry->max_stack) {
> +             fp = (unsigned long __user *) sp;
> +             if (!valid_user_sp(sp, 1) || read_user_stack_64(fp, &next_sp))
> +                     return;
> +             if (level > 0 && read_user_stack_64(&fp[2], &next_ip))
> +                     return;
> +
> +             /*
> +              * Note: the next_sp - sp >= signal frame size check
> +              * is true when next_sp < sp, which can happen when
> +              * transitioning from an alternate signal stack to the
> +              * normal stack.
> +              */
> +             if (next_sp - sp >= sizeof(struct signal_frame_64) &&
> +                 (is_sigreturn_64_address(next_ip, sp) ||
> +                  (level <= 1 && is_sigreturn_64_address(lr, sp))) &&
> +                 sane_signal_64_frame(sp)) {
> +                     /*
> +                      * This looks like an signal frame
> +                      */
> +                     sigframe = (struct signal_frame_64 __user *) sp;
> +                     uregs = sigframe->uc.uc_mcontext.gp_regs;
> +                     if (read_user_stack_64(&uregs[PT_NIP], &next_ip) ||
> +                         read_user_stack_64(&uregs[PT_LNK], &lr) ||
> +                         read_user_stack_64(&uregs[PT_R1], &sp))
> +                             return;
> +                     level = 0;
> +                     perf_callchain_store_context(entry, PERF_CONTEXT_USER);
> +                     perf_callchain_store(entry, next_ip);
> +                     continue;
> +             }
> +
> +             if (level == 0)
> +                     next_ip = lr;
> +             perf_callchain_store(entry, next_ip);
> +             ++level;
> +             sp = next_sp;
> +     }
> +}

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