Re: [PATCH 1/2] binfmt_elf_fdpic: support 64-bit systems

[Greg Ungerer <gerg@xxxxxxxxxx>]

Hi Palmer,

On 19/4/23 13:27, Palmer Dabbelt wrote:
> On Wed, 29 Mar 2023 06:48:55 PDT (-0700), gerg@xxxxxxxxxx wrote:
> > On 22/3/23 08:49, Palmer Dabbelt wrote:
> > > On Tue, 28 Feb 2023 05:51:25 PST (-0800), gerg@xxxxxxxxxx wrote:
> > > > The binfmt_flat_fdpic code has a number of 32-bit specific data
> > > > structures associated with it. Extend it to be able to support and
> > > > be used on 64-bit systems as well.
> > > >
> > > > The new code defines a number of key 64-bit variants of the core
> > > > elf-fdpic data structures - along side the existing 32-bit sized ones.
> > > > A common set of generic named structures are defined to be either
> > > > the 32-bit or 64-bit ones as required at compile time. This is a
> > > > similar technique to that used in the ELF binfmt loader.
> > > >
> > > > For example:
> > > >
> > > >   elf_fdpic_loadseg is either elf32_fdpic_loadseg or elf64_fdpic_loadseg
> > > >   elf_fdpic_loadmap is either elf32_fdpic_loadmap or elf64_fdpic_loadmap
> > > >
> > > > the choice based on ELFCLASS32 or ELFCLASS64.
> > > >
> > > > Signed-off-by: Greg Ungerer <gerg@xxxxxxxxxx>
> > > > ---
> > > >  fs/binfmt_elf_fdpic.c          | 38 +++++++++++++++++-----------------
> > > >  include/linux/elf-fdpic.h      | 14 ++++++++++++-
> > > >  include/uapi/linux/elf-fdpic.h | 15 ++++++++++++++
> > > >  3 files changed, 47 insertions(+), 20 deletions(-)
> > >
> > > Adding some of the binfmt/fs folks, who weren't directly on the mail. It's looking like we're generally OK with this in RISC-V land, though there's still no userspace posted.  I don't think there's any rush here and it might be prudent to wait for userspace to start going through a bit of a review, but figured I'd at least poke everyone to see if there's any thoughts.
> > >
> > > I'm fine either way, so
> > > Acked-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> > >
> > > if that helps any.  Also happy to take this through the RISC-V tree along with the other if that's easier, but again no rush.
> >
> > Just following up. I haven't seen any feedback on this - did I miss any?
>
> If you did then I did too.  I'm not really sure what to do here: it looks fine to me, but it's not really my area so I'd prefer to have someone who understands this stuff a bit better chime in.
>
> It looks like some Arm patches recently went in through that tree, though, so maybe that's how things are supposed to go here?

There doesn't seem to be anyone who is clearly the designated maintainer
for binfmt_elf_fdpic, or even just sheparding fixes for it. It mostly seems
to be tree-wide changes and cleanups that are getting done to it.

So I have no idea... I have at least one fix inside binfmt_elf_fdpic.c for
ARM architecture that I am preparing now too, not sure how that is going to
go either.

Regards
Greg



> > > > diff --git a/fs/binfmt_elf_fdpic.c b/fs/binfmt_elf_fdpic.c
> > > > index a05eafcacfb27..2eea6dd429fd6 100644
> > > > --- a/fs/binfmt_elf_fdpic.c
> > > > +++ b/fs/binfmt_elf_fdpic.c
> > > > @@ -138,7 +138,7 @@ static int is_constdisp(struct elfhdr *hdr)
> > > >  static int elf_fdpic_fetch_phdrs(struct elf_fdpic_params *params,
> > > >                   struct file *file)
> > > >  {
> > > > -    struct elf32_phdr *phdr;
> > > > +    struct elf_phdr *phdr;
> > > >      unsigned long size;
> > > >      int retval, loop;
> > > >      loff_t pos = params->hdr.e_phoff;
> > > > @@ -560,8 +560,8 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
> > > >      sp &= ~7UL;
> > > >
> > > >      /* stack the load map(s) */
> > > > -    len = sizeof(struct elf32_fdpic_loadmap);
> > > > -    len += sizeof(struct elf32_fdpic_loadseg) * exec_params->loadmap->nsegs;
> > > > +    len = sizeof(struct elf_fdpic_loadmap);
> > > > +    len += sizeof(struct elf_fdpic_loadseg) * exec_params->loadmap->nsegs;
> > > >      sp = (sp - len) & ~7UL;
> > > >      exec_params->map_addr = sp;
> > > >
> > > > @@ -571,8 +571,8 @@ static int create_elf_fdpic_tables(struct linux_binprm *bprm,
> > > >      current->mm->context.exec_fdpic_loadmap = (unsigned long) sp;
> > > >
> > > >      if (interp_params->loadmap) {
> > > > -        len = sizeof(struct elf32_fdpic_loadmap);
> > > > -        len += sizeof(struct elf32_fdpic_loadseg) *
> > > > +        len = sizeof(struct elf_fdpic_loadmap);
> > > > +        len += sizeof(struct elf_fdpic_loadseg) *
> > > >              interp_params->loadmap->nsegs;
> > > >          sp = (sp - len) & ~7UL;
> > > >          interp_params->map_addr = sp;
> > > > @@ -740,12 +740,12 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
> > > >                    struct mm_struct *mm,
> > > >                    const char *what)
> > > >  {
> > > > -    struct elf32_fdpic_loadmap *loadmap;
> > > > +    struct elf_fdpic_loadmap *loadmap;
> > > >  #ifdef CONFIG_MMU
> > > > -    struct elf32_fdpic_loadseg *mseg;
> > > > +    struct elf_fdpic_loadseg *mseg;
> > > >  #endif
> > > > -    struct elf32_fdpic_loadseg *seg;
> > > > -    struct elf32_phdr *phdr;
> > > > +    struct elf_fdpic_loadseg *seg;
> > > > +    struct elf_phdr *phdr;
> > > >      unsigned long load_addr, stop;
> > > >      unsigned nloads, tmp;
> > > >      size_t size;
> > > > @@ -767,7 +767,7 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
> > > >
> > > >      params->loadmap = loadmap;
> > > >
> > > > -    loadmap->version = ELF32_FDPIC_LOADMAP_VERSION;
> > > > +    loadmap->version = ELF_FDPIC_LOADMAP_VERSION;
> > > >      loadmap->nsegs = nloads;
> > > >
> > > >      load_addr = params->load_addr;
> > > > @@ -843,8 +843,8 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
> > > >              if (phdr->p_vaddr >= seg->p_vaddr &&
> > > >                  phdr->p_vaddr + phdr->p_memsz <=
> > > >                  seg->p_vaddr + seg->p_memsz) {
> > > > -                Elf32_Dyn __user *dyn;
> > > > -                Elf32_Sword d_tag;
> > > > +                Elf_Dyn __user *dyn;
> > > > +                Elf_Sword d_tag;
> > > >
> > > >                  params->dynamic_addr =
> > > >                      (phdr->p_vaddr - seg->p_vaddr) +
> > > > @@ -854,11 +854,11 @@ static int elf_fdpic_map_file(struct elf_fdpic_params *params,
> > > >                   * one item, and that the last item is a NULL
> > > >                   * entry */
> > > >                  if (phdr->p_memsz == 0 ||
> > > > -                    phdr->p_memsz % sizeof(Elf32_Dyn) != 0)
> > > > +                    phdr->p_memsz % sizeof(Elf_Dyn) != 0)
> > > >                      goto dynamic_error;
> > > >
> > > > -                tmp = phdr->p_memsz / sizeof(Elf32_Dyn);
> > > > -                dyn = (Elf32_Dyn __user *)params->dynamic_addr;
> > > > +                tmp = phdr->p_memsz / sizeof(Elf_Dyn);
> > > > +                dyn = (Elf_Dyn __user *)params->dynamic_addr;
> > > >                  if (get_user(d_tag, &dyn[tmp - 1].d_tag) ||
> > > >                      d_tag != 0)
> > > >                      goto dynamic_error;
> > > > @@ -927,8 +927,8 @@ static int elf_fdpic_map_file_constdisp_on_uclinux(
> > > >      struct file *file,
> > > >      struct mm_struct *mm)
> > > >  {
> > > > -    struct elf32_fdpic_loadseg *seg;
> > > > -    struct elf32_phdr *phdr;
> > > > +    struct elf_fdpic_loadseg *seg;
> > > > +    struct elf_phdr *phdr;
> > > >      unsigned long load_addr, base = ULONG_MAX, top = 0, maddr = 0;
> > > >      int loop, ret;
> > > >
> > > > @@ -1011,8 +1011,8 @@ static int elf_fdpic_map_file_by_direct_mmap(struct elf_fdpic_params *params,
> > > >                           struct file *file,
> > > >                           struct mm_struct *mm)
> > > >  {
> > > > -    struct elf32_fdpic_loadseg *seg;
> > > > -    struct elf32_phdr *phdr;
> > > > +    struct elf_fdpic_loadseg *seg;
> > > > +    struct elf_phdr *phdr;
> > > >      unsigned long load_addr, delta_vaddr;
> > > >      int loop, dvset;
> > > >
> > > > diff --git a/include/linux/elf-fdpic.h b/include/linux/elf-fdpic.h
> > > > index 3bea95a1af537..e533f45131945 100644
> > > > --- a/include/linux/elf-fdpic.h
> > > > +++ b/include/linux/elf-fdpic.h
> > > > @@ -10,13 +10,25 @@
> > > >
> > > >  #include <uapi/linux/elf-fdpic.h>
> > > >
> > > > +#if ELF_CLASS == ELFCLASS32
> > > > +#define Elf_Sword            Elf32_Sword
> > > > +#define elf_fdpic_loadseg        elf32_fdpic_loadseg
> > > > +#define elf_fdpic_loadmap        elf32_fdpic_loadmap
> > > > +#define ELF_FDPIC_LOADMAP_VERSION    ELF32_FDPIC_LOADMAP_VERSION
> > > > +#else
> > > > +#define Elf_Sword            Elf64_Sxword
> > > > +#define elf_fdpic_loadmap        elf64_fdpic_loadmap
> > > > +#define elf_fdpic_loadseg        elf64_fdpic_loadseg
> > > > +#define ELF_FDPIC_LOADMAP_VERSION    ELF64_FDPIC_LOADMAP_VERSION
> > > > +#endif
> > > > +
> > > >  /*
> > > >   * binfmt binary parameters structure
> > > >   */
> > > >  struct elf_fdpic_params {
> > > >      struct elfhdr            hdr;        /* ref copy of ELF header */
> > > >      struct elf_phdr            *phdrs;        /* ref copy of PT_PHDR table */
> > > > -    struct elf32_fdpic_loadmap    *loadmap;    /* loadmap to be passed to userspace */
> > > > +    struct elf_fdpic_loadmap    *loadmap;    /* loadmap to be passed to userspace */
> > > >      unsigned long            elfhdr_addr;    /* mapped ELF header user address */
> > > >      unsigned long            ph_addr;    /* mapped PT_PHDR user address */
> > > >      unsigned long            map_addr;    /* mapped loadmap user address */
> > > > diff --git a/include/uapi/linux/elf-fdpic.h b/include/uapi/linux/elf-fdpic.h
> > > > index 4fcc6cfebe185..ec23f08711292 100644
> > > > --- a/include/uapi/linux/elf-fdpic.h
> > > > +++ b/include/uapi/linux/elf-fdpic.h
> > > > @@ -32,4 +32,19 @@ struct elf32_fdpic_loadmap {
> > > >
> > > >  #define ELF32_FDPIC_LOADMAP_VERSION    0x0000
> > > >
> > > > +/* segment mappings for ELF FDPIC libraries/executables/interpreters */
> > > > +struct elf64_fdpic_loadseg {
> > > > +    Elf64_Addr    addr;        /* core address to which mapped */
> > > > +    Elf64_Addr    p_vaddr;    /* VMA recorded in file */
> > > > +    Elf64_Word    p_memsz;    /* allocation size recorded in file */
> > > > +};
> > > > +
> > > > +struct elf64_fdpic_loadmap {
> > > > +    Elf64_Half    version;    /* version of these structures, just in case... */
> > > > +    Elf64_Half    nsegs;        /* number of segments */
> > > > +    struct elf64_fdpic_loadseg segs[];
> > > > +};
> > > > +
> > > > +#define ELF64_FDPIC_LOADMAP_VERSION    0x0000
> > > > +
> > > >  #endif /* _UAPI_LINUX_ELF_FDPIC_H */