[v6,2/8] libcamera: ipa_module: Factor out ELF file handling

26030 diff mbox series

In the near future we will add support for layers/shoes on top of
libcamera, which will need to validate and load symbols from ELF files
similar to how IPAModule does. To avoid code duplication, move this code
out of IPAModule into internal utils.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
---
No change in v6

No change in v5

No change in v4

Changes in v3:
- add documentation for elfVerifyIdent

No change in v2
---
 include/libcamera/internal/utils.h |   6 ++
 src/libcamera/ipa_module.cpp       | 152 +--------------------------
 src/libcamera/utils.cpp            | 162 +++++++++++++++++++++++++++++
 3 files changed, 171 insertions(+), 149 deletions(-)

Hi Paul,

Looks good to me!

Quoting Paul Elder (2026-01-29 08:28:08)
> In the near future we will add support for layers/shoes on top of
> libcamera, which will need to validate and load symbols from ELF files
> similar to how IPAModule does. To avoid code duplication, move this code
> out of IPAModule into internal utils.
> 
> Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
> Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
> ---
> No change in v6
> 
> No change in v5
> 
> No change in v4
> 
> Changes in v3:
> - add documentation for elfVerifyIdent
> 
> No change in v2
> ---
>  include/libcamera/internal/utils.h |   6 ++
>  src/libcamera/ipa_module.cpp       | 152 +--------------------------
>  src/libcamera/utils.cpp            | 162 +++++++++++++++++++++++++++++
>  3 files changed, 171 insertions(+), 149 deletions(-)
> 
> diff --git a/include/libcamera/internal/utils.h b/include/libcamera/internal/utils.h
> index 5b7957b5d77e..7d69849b1c19 100644
> --- a/include/libcamera/internal/utils.h
> +++ b/include/libcamera/internal/utils.h
> @@ -8,9 +8,12 @@
>  #pragma once
>  
>  #include <functional>
> +#include <stdint.h>
>  #include <string>
>  #include <vector>
>  
> +#include <libcamera/base/span.h>
> +
>  namespace libcamera {
>  
>  namespace utils {
> @@ -18,6 +21,9 @@ namespace utils {
>  unsigned int findSharedObjects(const char *libDir, unsigned int maxDepth,
>                                std::function<int(const std::string &)> func);

Reviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>

Best wishes,
Isaac

>  
> +int elfVerifyIdent(Span<const uint8_t> elf);
> +Span<const uint8_t> elfLoadSymbol(Span<const uint8_t> elf, const char *symbol);
> +
>  } /* namespace utils */
>  
>  } /* namespace libcamera */
> diff --git a/src/libcamera/ipa_module.cpp b/src/libcamera/ipa_module.cpp
> index e6ea61e44829..c8559ec8b74c 100644
> --- a/src/libcamera/ipa_module.cpp
> +++ b/src/libcamera/ipa_module.cpp
> @@ -25,6 +25,7 @@
>  #include <libcamera/base/utils.h>
>  
>  #include "libcamera/internal/pipeline_handler.h"
> +#include "libcamera/internal/utils.h"
>  
>  /**
>   * \file ipa_module.h
> @@ -40,153 +41,6 @@ namespace libcamera {
>  
>  LOG_DEFINE_CATEGORY(IPAModule)
>  
> -namespace {
> -
> -template<typename T>
> -typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,
> -                                            off_t offset, size_t objSize)
> -{
> -       size_t size = offset + objSize;
> -       if (size > elf.size() || size < objSize)
> -               return nullptr;
> -
> -       return reinterpret_cast<typename std::remove_extent_t<T> *>(
> -               reinterpret_cast<const char *>(elf.data()) + offset);
> -}
> -
> -template<typename T>
> -typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,
> -                                            off_t offset)
> -{
> -       return elfPointer<T>(elf, offset, sizeof(T));
> -}
> -
> -int elfVerifyIdent(Span<const uint8_t> elf)
> -{
> -       const char *e_ident = elfPointer<const char[EI_NIDENT]>(elf, 0);
> -       if (!e_ident)
> -               return -ENOEXEC;
> -
> -       if (e_ident[EI_MAG0] != ELFMAG0 ||
> -           e_ident[EI_MAG1] != ELFMAG1 ||
> -           e_ident[EI_MAG2] != ELFMAG2 ||
> -           e_ident[EI_MAG3] != ELFMAG3 ||
> -           e_ident[EI_VERSION] != EV_CURRENT)
> -               return -ENOEXEC;
> -
> -       int bitClass = sizeof(unsigned long) == 4 ? ELFCLASS32 : ELFCLASS64;
> -       if (e_ident[EI_CLASS] != bitClass)
> -               return -ENOEXEC;
> -
> -       int a = 1;
> -       unsigned char endianness = *reinterpret_cast<char *>(&a) == 1
> -                                ? ELFDATA2LSB : ELFDATA2MSB;
> -       if (e_ident[EI_DATA] != endianness)
> -               return -ENOEXEC;
> -
> -       return 0;
> -}
> -
> -const ElfW(Shdr) *elfSection(Span<const uint8_t> elf, const ElfW(Ehdr) *eHdr,
> -                            ElfW(Half) idx)
> -{
> -       if (idx >= eHdr->e_shnum)
> -               return nullptr;
> -
> -       off_t offset = eHdr->e_shoff + idx *
> -                                      static_cast<uint32_t>(eHdr->e_shentsize);
> -       return elfPointer<const ElfW(Shdr)>(elf, offset);
> -}
> -
> -/**
> - * \brief Retrieve address and size of a symbol from an mmap'ed ELF file
> - * \param[in] elf Address and size of mmap'ed ELF file
> - * \param[in] symbol Symbol name
> - *
> - * \return The memory region storing the symbol on success, or an empty span
> - * otherwise
> - */
> -Span<const uint8_t> elfLoadSymbol(Span<const uint8_t> elf, const char *symbol)
> -{
> -       const ElfW(Ehdr) *eHdr = elfPointer<const ElfW(Ehdr)>(elf, 0);
> -       if (!eHdr)
> -               return {};
> -
> -       const ElfW(Shdr) *sHdr = elfSection(elf, eHdr, eHdr->e_shstrndx);
> -       if (!sHdr)
> -               return {};
> -       off_t shnameoff = sHdr->sh_offset;
> -
> -       /* Locate .dynsym section header. */
> -       const ElfW(Shdr) *dynsym = nullptr;
> -       for (unsigned int i = 0; i < eHdr->e_shnum; i++) {
> -               sHdr = elfSection(elf, eHdr, i);
> -               if (!sHdr)
> -                       return {};
> -
> -               off_t offset = shnameoff + sHdr->sh_name;
> -               const char *name = elfPointer<const char[8]>(elf, offset);
> -               if (!name)
> -                       return {};
> -
> -               if (sHdr->sh_type == SHT_DYNSYM && !strcmp(name, ".dynsym")) {
> -                       dynsym = sHdr;
> -                       break;
> -               }
> -       }
> -
> -       if (dynsym == nullptr) {
> -               LOG(IPAModule, Error) << "ELF has no .dynsym section";
> -               return {};
> -       }
> -
> -       sHdr = elfSection(elf, eHdr, dynsym->sh_link);
> -       if (!sHdr)
> -               return {};
> -       off_t dynsym_nameoff = sHdr->sh_offset;
> -
> -       /* Locate symbol in the .dynsym section. */
> -       const ElfW(Sym) *targetSymbol = nullptr;
> -       unsigned int dynsym_num = dynsym->sh_size / dynsym->sh_entsize;
> -       for (unsigned int i = 0; i < dynsym_num; i++) {
> -               off_t offset = dynsym->sh_offset + dynsym->sh_entsize * i;
> -               const ElfW(Sym) *sym = elfPointer<const ElfW(Sym)>(elf, offset);
> -               if (!sym)
> -                       return {};
> -
> -               offset = dynsym_nameoff + sym->st_name;
> -               const char *name = elfPointer<const char>(elf, offset,
> -                                                         strlen(symbol) + 1);
> -               if (!name)
> -                       return {};
> -
> -               if (!strcmp(name, symbol) &&
> -                   sym->st_info & STB_GLOBAL) {
> -                       targetSymbol = sym;
> -                       break;
> -               }
> -       }
> -
> -       if (targetSymbol == nullptr) {
> -               LOG(IPAModule, Error) << "Symbol " << symbol << " not found";
> -               return {};
> -       }
> -
> -       /* Locate and return data of symbol. */
> -       sHdr = elfSection(elf, eHdr, targetSymbol->st_shndx);
> -       if (!sHdr)
> -               return {};
> -       off_t offset = sHdr->sh_offset + (targetSymbol->st_value - sHdr->sh_addr);
> -       const uint8_t *data = elfPointer<const uint8_t>(elf, offset,
> -                                                       targetSymbol->st_size);
> -       if (!data)
> -               return {};
> -
> -       return { data, targetSymbol->st_size };
> -}
> -
> -} /* namespace */
> -
>  /**
>   * \def IPA_MODULE_API_VERSION
>   * \brief The IPA module API version
> @@ -280,13 +134,13 @@ int IPAModule::loadIPAModuleInfo()
>         }
>  
>         Span<const uint8_t> data = file.map();
> -       int ret = elfVerifyIdent(data);
> +       int ret = utils::elfVerifyIdent(data);
>         if (ret) {
>                 LOG(IPAModule, Error) << "IPA module is not an ELF file";
>                 return ret;
>         }
>  
> -       Span<const uint8_t> info = elfLoadSymbol(data, "ipaModuleInfo");
> +       Span<const uint8_t> info = utils::elfLoadSymbol(data, "ipaModuleInfo");
>         if (info.size() < sizeof(info_)) {
>                 LOG(IPAModule, Error) << "IPA module has no valid info";
>                 return -EINVAL;
> diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp
> index 2ce62f236cea..6894b489b557 100644
> --- a/src/libcamera/utils.cpp
> +++ b/src/libcamera/utils.cpp
> @@ -10,20 +10,63 @@
>  #include <algorithm>
>  #include <dirent.h>
>  #include <functional>
> +#include <link.h>
> +#include <stdint.h>
>  #include <string.h>
>  #include <string>
>  #include <sys/types.h>
>  #include <vector>
>  
> +#include <libcamera/base/log.h>
> +
>  /**
>   * \file internal/utils.h
>   * \brief Miscellaneous utility functions (internal)
>   */
>  
> +/* musl doesn't declare _DYNAMIC in link.h, declare it manually. */
> +extern ElfW(Dyn) _DYNAMIC[];
> +
>  namespace libcamera {
>  
> +namespace {
> +
> +template<typename T>
> +typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,
> +                                            off_t offset, size_t objSize)
> +{
> +       size_t size = offset + objSize;
> +       if (size > elf.size() || size < objSize)
> +               return nullptr;
> +
> +       return reinterpret_cast<typename std::remove_extent_t<T> *>(
> +               reinterpret_cast<const char *>(elf.data()) + offset);
> +}
> +
> +template<typename T>
> +typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,
> +                                            off_t offset)
> +{
> +       return elfPointer<T>(elf, offset, sizeof(T));
> +}
> +
> +const ElfW(Shdr) *elfSection(Span<const uint8_t> elf, const ElfW(Ehdr) *eHdr,
> +                            ElfW(Half) idx)
> +{
> +       if (idx >= eHdr->e_shnum)
> +               return nullptr;
> +
> +       off_t offset = eHdr->e_shoff + idx *
> +                                      static_cast<uint32_t>(eHdr->e_shentsize);
> +       return elfPointer<const ElfW(Shdr)>(elf, offset);
> +}
> +
> +} /* namespace */
> +
>  namespace utils {
>  
> +LOG_DEFINE_CATEGORY(Utils)
> +
>  /**
>   * \brief Identify shared library objects within a directory
>   * \param[in] libDir The directory to search for shared objects
> @@ -102,6 +145,125 @@ unsigned int findSharedObjects(const char *libDir, unsigned int maxDepth,
>         return count;
>  }
>  
> +/**
> + * \brief Verify that a binary blob is an ELF
> + * \param[in] elf The binary blob as a Span
> + *
> + * \return 0 for success, and -ENOEXEC otherwise
> + */
> +int elfVerifyIdent(Span<const uint8_t> elf)
> +{
> +       const char *e_ident = elfPointer<const char[EI_NIDENT]>(elf, 0);
> +       if (!e_ident)
> +               return -ENOEXEC;
> +
> +       if (e_ident[EI_MAG0] != ELFMAG0 ||
> +           e_ident[EI_MAG1] != ELFMAG1 ||
> +           e_ident[EI_MAG2] != ELFMAG2 ||
> +           e_ident[EI_MAG3] != ELFMAG3 ||
> +           e_ident[EI_VERSION] != EV_CURRENT)
> +               return -ENOEXEC;
> +
> +       int bitClass = sizeof(unsigned long) == 4 ? ELFCLASS32 : ELFCLASS64;
> +       if (e_ident[EI_CLASS] != bitClass)
> +               return -ENOEXEC;
> +
> +       int a = 1;
> +       unsigned char endianness = *reinterpret_cast<char *>(&a) == 1
> +                                ? ELFDATA2LSB : ELFDATA2MSB;
> +       if (e_ident[EI_DATA] != endianness)
> +               return -ENOEXEC;
> +
> +       return 0;
> +}
> +
> +/**
> + * \brief Retrieve address and size of a symbol from an mmap'ed ELF file
> + * \param[in] elf Address and size of mmap'ed ELF file
> + * \param[in] symbol Symbol name
> + *
> + * \return The memory region storing the symbol on success, or an empty span
> + * otherwise
> + */
> +Span<const uint8_t> elfLoadSymbol(Span<const uint8_t> elf, const char *symbol)
> +{
> +       const ElfW(Ehdr) *eHdr = elfPointer<const ElfW(Ehdr)>(elf, 0);
> +       if (!eHdr)
> +               return {};
> +
> +       const ElfW(Shdr) *sHdr = elfSection(elf, eHdr, eHdr->e_shstrndx);
> +       if (!sHdr)
> +               return {};
> +       off_t shnameoff = sHdr->sh_offset;
> +
> +       /* Locate .dynsym section header. */
> +       const ElfW(Shdr) *dynsym = nullptr;
> +       for (unsigned int i = 0; i < eHdr->e_shnum; i++) {
> +               sHdr = elfSection(elf, eHdr, i);
> +               if (!sHdr)
> +                       return {};
> +
> +               off_t offset = shnameoff + sHdr->sh_name;
> +               const char *name = elfPointer<const char[8]>(elf, offset);
> +               if (!name)
> +                       return {};
> +
> +               if (sHdr->sh_type == SHT_DYNSYM && !strcmp(name, ".dynsym")) {
> +                       dynsym = sHdr;
> +                       break;
> +               }
> +       }
> +
> +       if (dynsym == nullptr) {
> +               LOG(Utils, Error) << "ELF has no .dynsym section";
> +               return {};
> +       }
> +
> +       sHdr = elfSection(elf, eHdr, dynsym->sh_link);
> +       if (!sHdr)
> +               return {};
> +       off_t dynsym_nameoff = sHdr->sh_offset;
> +
> +       /* Locate symbol in the .dynsym section. */
> +       const ElfW(Sym) *targetSymbol = nullptr;
> +       unsigned int dynsym_num = dynsym->sh_size / dynsym->sh_entsize;
> +       for (unsigned int i = 0; i < dynsym_num; i++) {
> +               off_t offset = dynsym->sh_offset + dynsym->sh_entsize * i;
> +               const ElfW(Sym) *sym = elfPointer<const ElfW(Sym)>(elf, offset);
> +               if (!sym)
> +                       return {};
> +
> +               offset = dynsym_nameoff + sym->st_name;
> +               const char *name = elfPointer<const char>(elf, offset,
> +                                                         strlen(symbol) + 1);
> +               if (!name)
> +                       return {};
> +
> +               if (!strcmp(name, symbol) &&
> +                   sym->st_info & STB_GLOBAL) {
> +                       targetSymbol = sym;
> +                       break;
> +               }
> +       }
> +
> +       if (targetSymbol == nullptr) {
> +               LOG(Utils, Error) << "Symbol " << symbol << " not found";
> +               return {};
> +       }
> +
> +       /* Locate and return data of symbol. */
> +       sHdr = elfSection(elf, eHdr, targetSymbol->st_shndx);
> +       if (!sHdr)
> +               return {};
> +       off_t offset = sHdr->sh_offset + (targetSymbol->st_value - sHdr->sh_addr);
> +       const uint8_t *data = elfPointer<const uint8_t>(elf, offset,
> +                                                       targetSymbol->st_size);
> +       if (!data)
> +               return {};
> +
> +       return { data, targetSymbol->st_size };
> +}
> +
>  } /* namespace utils */
>  
>  } /* namespace libcamera */
> -- 
> 2.47.2
>