Re: [PATCH V5 17/21] riscv: compat: vdso: Add setup additional pages implementation

Palmer Dabbelt
2022-02-23T01:43:27Z

On Tue, 01 Feb 2022 07:05:41 PST (-0800), guoren@kernel.org wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
>
> Reconstruct __setup_additional_pages() by appending vdso info
> pointer argument to meet compat_vdso_info requirement. And change
> vm_special_mapping *dm, *cm initialization into static.
>
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> Cc: Arnd Bergmann <arnd@arndb.de>
> Cc: Palmer Dabbelt <palmer@dabbelt.com>
> ---
> arch/riscv/include/asm/elf.h | 5 ++
> arch/riscv/include/asm/mmu.h | 1 +
> arch/riscv/kernel/vdso.c | 104 +++++++++++++++++++++++++----------
> 3 files changed, 81 insertions(+), 29 deletions(-)
>
> diff --git a/arch/riscv/include/asm/elf.h b/arch/riscv/include/asm/elf.h
> index 3a4293dc7229..d87d3bcc758d 100644
> --- a/arch/riscv/include/asm/elf.h
> +++ b/arch/riscv/include/asm/elf.h
> @@ -134,5 +134,10 @@ do { if ((ex).e_ident[EI_CLASS] == ELFCLASS32) \
> typedef compat_ulong_t compat_elf_greg_t;
> typedef compat_elf_greg_t compat_elf_gregset_t[ELF_NGREG];
>
> +extern int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
> + int uses_interp);
> +#define compat_arch_setup_additional_pages \
> + compat_arch_setup_additional_pages
> +
> #endif /* CONFIG_COMPAT */
> #endif /* _ASM_RISCV_ELF_H */
> diff --git a/arch/riscv/include/asm/mmu.h b/arch/riscv/include/asm/mmu.h
> index 0099dc116168..cedcf8ea3c76 100644
> --- a/arch/riscv/include/asm/mmu.h
> +++ b/arch/riscv/include/asm/mmu.h
> @@ -16,6 +16,7 @@ typedef struct {
> atomic_long_t id;
> #endif
> void *vdso;
> + void *vdso_info;
> #ifdef CONFIG_SMP
> /* A local icache flush is needed before user execution can resume. */
> cpumask_t icache_stale_mask;
> diff --git a/arch/riscv/kernel/vdso.c b/arch/riscv/kernel/vdso.c
> index a9436a65161a..deca69524799 100644
> --- a/arch/riscv/kernel/vdso.c
> +++ b/arch/riscv/kernel/vdso.c
> @@ -23,6 +23,9 @@ struct vdso_data {
> #endif
>
> extern char vdso_start[], vdso_end[];
> +#ifdef CONFIG_COMPAT
> +extern char compat_vdso_start[], compat_vdso_end[];
> +#endif
>
> enum vvar_pages {
> VVAR_DATA_PAGE_OFFSET,
> @@ -30,6 +33,11 @@ enum vvar_pages {
> VVAR_NR_PAGES,
> };
>
> +enum rv_vdso_map {
> + RV_VDSO_MAP_VVAR,
> + RV_VDSO_MAP_VDSO,
> +};
> +
> #define VVAR_SIZE (VVAR_NR_PAGES << PAGE_SHIFT)
>
> /*
> @@ -52,12 +60,6 @@ struct __vdso_info {
> struct vm_special_mapping *cm;
> };
>
> -static struct __vdso_info vdso_info __ro_after_init = {
> - .name = "vdso",
> - .vdso_code_start = vdso_start,
> - .vdso_code_end = vdso_end,
> -};
> -
> static int vdso_mremap(const struct vm_special_mapping *sm,
> struct vm_area_struct *new_vma)
> {
> @@ -66,35 +68,35 @@ static int vdso_mremap(const struct vm_special_mapping *sm,
> return 0;
> }
>
> -static int __init __vdso_init(void)
> +static int __init __vdso_init(struct __vdso_info *vdso_info)
> {
> unsigned int i;
> struct page **vdso_pagelist;
> unsigned long pfn;
>
> - if (memcmp(vdso_info.vdso_code_start, "\177ELF", 4)) {
> + if (memcmp(vdso_info->vdso_code_start, "\177ELF", 4)) {
> pr_err("vDSO is not a valid ELF object!\n");
> return -EINVAL;
> }
>
> - vdso_info.vdso_pages = (
> - vdso_info.vdso_code_end -
> - vdso_info.vdso_code_start) >>
> + vdso_info->vdso_pages = (
> + vdso_info->vdso_code_end -
> + vdso_info->vdso_code_start) >>
> PAGE_SHIFT;
>
> - vdso_pagelist = kcalloc(vdso_info.vdso_pages,
> + vdso_pagelist = kcalloc(vdso_info->vdso_pages,
> sizeof(struct page *),
> GFP_KERNEL);
> if (vdso_pagelist == NULL)
> return -ENOMEM;
>
> /* Grab the vDSO code pages. */
> - pfn = sym_to_pfn(vdso_info.vdso_code_start);
> + pfn = sym_to_pfn(vdso_info->vdso_code_start);
>
> - for (i = 0; i < vdso_info.vdso_pages; i++)
> + for (i = 0; i < vdso_info->vdso_pages; i++)
> vdso_pagelist[i] = pfn_to_page(pfn + i);
>
> - vdso_info.cm->pages = vdso_pagelist;
> + vdso_info->cm->pages = vdso_pagelist;
>
> return 0;
> }
> @@ -116,13 +118,14 @@ int vdso_join_timens(struct task_struct *task, struct time_namespace *ns)
> {
> struct mm_struct *mm = task->mm;
> struct vm_area_struct *vma;
> + struct __vdso_info *vdso_info = mm->context.vdso_info;

IIUC this is the only use for context.vdso_info? If that's the case,
can we just switch between VDSO targets based on __is_compat_task(task)?
That'd save an mm_struct pointer, which is always nice. It'd probably
be worth cleaning up the arm64 port too, which zaps both mappings.

>
> mmap_read_lock(mm);
>
> for (vma = mm->mmap; vma; vma = vma->vm_next) {
> unsigned long size = vma->vm_end - vma->vm_start;
>
> - if (vma_is_special_mapping(vma, vdso_info.dm))
> + if (vma_is_special_mapping(vma, vdso_info->dm))
> zap_page_range(vma, vma->vm_start, size);
> }
>
> @@ -187,11 +190,6 @@ static vm_fault_t vvar_fault(const struct vm_special_mapping *sm,
> return vmf_insert_pfn(vma, vmf->address, pfn);
> }
>
> -enum rv_vdso_map {
> - RV_VDSO_MAP_VVAR,
> - RV_VDSO_MAP_VDSO,
> -};
> -
> static struct vm_special_mapping rv_vdso_maps[] __ro_after_init = {
> [RV_VDSO_MAP_VVAR] = {
> .name = "[vvar]",
> @@ -203,25 +201,53 @@ static struct vm_special_mapping rv_vdso_maps[] __ro_after_init = {
> },
> };
>
> +static struct __vdso_info vdso_info __ro_after_init = {
> + .name = "vdso",
> + .vdso_code_start = vdso_start,
> + .vdso_code_end = vdso_end,
> + .dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR],
> + .cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO],
> +};
> +
> +#ifdef CONFIG_COMPAT
> +static struct __vdso_info compat_vdso_info __ro_after_init = {
> + .name = "compat_vdso",
> + .vdso_code_start = compat_vdso_start,
> + .vdso_code_end = compat_vdso_end,
> + .dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR],
> + .cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO],
> +};
> +#endif
> +
> static int __init vdso_init(void)
> {
> - vdso_info.dm = &rv_vdso_maps[RV_VDSO_MAP_VVAR];
> - vdso_info.cm = &rv_vdso_maps[RV_VDSO_MAP_VDSO];
> + int ret;
> +
> + ret = __vdso_init(&vdso_info);
> + if (ret)
> + goto out;
>
> - return __vdso_init();
> +#ifdef CONFIG_COMPAT
> + ret = __vdso_init(&compat_vdso_info);
> + if (ret)
> + goto out;

It's a bit pedantic (we're just going to crash anyway), but this is
mising the cleanup for the first __vdso_init().

> +#endif
> +out:
> + return ret;
> }
> arch_initcall(vdso_init);
>
> static int __setup_additional_pages(struct mm_struct *mm,
> struct linux_binprm *bprm,
> - int uses_interp)
> + int uses_interp,
> + struct __vdso_info *vdso_info)
> {
> unsigned long vdso_base, vdso_text_len, vdso_mapping_len;
> void *ret;
>
> BUILD_BUG_ON(VVAR_NR_PAGES != __VVAR_PAGES);
>
> - vdso_text_len = vdso_info.vdso_pages << PAGE_SHIFT;
> + vdso_text_len = vdso_info->vdso_pages << PAGE_SHIFT;
> /* Be sure to map the data page */
> vdso_mapping_len = vdso_text_len + VVAR_SIZE;
>
> @@ -232,16 +258,18 @@ static int __setup_additional_pages(struct mm_struct *mm,
> }
>
> ret = _install_special_mapping(mm, vdso_base, VVAR_SIZE,
> - (VM_READ | VM_MAYREAD | VM_PFNMAP), vdso_info.dm);
> + (VM_READ | VM_MAYREAD | VM_PFNMAP), vdso_info->dm);
> if (IS_ERR(ret))
> goto up_fail;
>
> vdso_base += VVAR_SIZE;
> mm->context.vdso = (void *)vdso_base;
> + mm->context.vdso_info = (void *)vdso_info;
> +
> ret =
> _install_special_mapping(mm, vdso_base, vdso_text_len,
> (VM_READ | VM_EXEC | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC),
> - vdso_info.cm);
> + vdso_info->cm);
>
> if (IS_ERR(ret))
> goto up_fail;
> @@ -253,6 +281,24 @@ static int __setup_additional_pages(struct mm_struct *mm,
> return PTR_ERR(ret);
> }
>
> +#ifdef CONFIG_COMPAT
> +int compat_arch_setup_additional_pages(struct linux_binprm *bprm,
> + int uses_interp)
> +{
> + struct mm_struct *mm = current->mm;
> + int ret;
> +
> + if (mmap_write_lock_killable(mm))
> + return -EINTR;
> +
> + ret = __setup_additional_pages(mm, bprm, uses_interp,
> + &compat_vdso_info);
> + mmap_write_unlock(mm);
> +
> + return ret;
> +}
> +#endif
> +
> int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
> {
> struct mm_struct *mm = current->mm;
> @@ -261,7 +307,7 @@ int arch_setup_additional_pages(struct linux_binprm *bprm, int uses_interp)
> if (mmap_write_lock_killable(mm))
> return -EINTR;
>
> - ret = __setup_additional_pages(mm, bprm, uses_interp);
> + ret = __setup_additional_pages(mm, bprm, uses_interp, &vdso_info);
> mmap_write_unlock(mm);
>
> return ret;

Reviewed-by: Palmer Dabbelt <palmer@rivosinc.com>

As I don't think either of these are big enough of a deal to keep from merging
this.