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Message-ID: <ab995c62-e537-a57e-062e-28aea2a4e6e5@kernel.org>
Date:   Wed, 29 Mar 2023 23:48:55 +1000
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Subject: Re: [PATCH 1/2] binfmt_elf_fdpic: support 64-bit systems
Content-Language: en-US
To:     Palmer Dabbelt <palmer@dabbelt.com>, viro@zeniv.linux.org.uk,
        brauner@kernel.org, ebiederm@xmission.com, keescook@chromium.org
Cc:     linux-riscv@lists.infradead.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
References: <mhng-fec49316-5da9-4cab-af79-6115f13668c1@palmer-ri-x1c9a>
From:   Greg Ungerer <gerg@kernel.org>
In-Reply-To: <mhng-fec49316-5da9-4cab-af79-6115f13668c1@palmer-ri-x1c9a>
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On 22/3/23 08:49, Palmer Dabbelt wrote:
> On Tue, 28 Feb 2023 05:51:25 PST (-0800), gerg@kernel.org 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@kernel.org>
>> ---
>>  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@rivosinc.com>
> 
> 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?

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 */
>