[{"id":38284,"web_url":"https://patchwork.libcamera.org/comment/38284/","msgid":"<177193158251.1513537.11582418644740584362@t16>","date":"2026-02-24T11:13:02","subject":"Re: [PATCH v6 2/8] libcamera: ipa_module: Factor out ELF file\n\thandling","submitter":{"id":215,"url":"https://patchwork.libcamera.org/api/people/215/","name":"Isaac Scott","email":"isaac.scott@ideasonboard.com"},"content":"Hi Paul,\n\nLooks good to me!\n\nQuoting Paul Elder (2026-01-29 08:28:08)\n> In the near future we will add support for layers/shoes on top of\n> libcamera, which will need to validate and load symbols from ELF files\n> similar to how IPAModule does. To avoid code duplication, move this code\n> out of IPAModule into internal utils.\n> \n> Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>\n> Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>\n> ---\n> No change in v6\n> \n> No change in v5\n> \n> No change in v4\n> \n> Changes in v3:\n> - add documentation for elfVerifyIdent\n> \n> No change in v2\n> ---\n>  include/libcamera/internal/utils.h |   6 ++\n>  src/libcamera/ipa_module.cpp       | 152 +--------------------------\n>  src/libcamera/utils.cpp            | 162 +++++++++++++++++++++++++++++\n>  3 files changed, 171 insertions(+), 149 deletions(-)\n> \n> diff --git a/include/libcamera/internal/utils.h b/include/libcamera/internal/utils.h\n> index 5b7957b5d77e..7d69849b1c19 100644\n> --- a/include/libcamera/internal/utils.h\n> +++ b/include/libcamera/internal/utils.h\n> @@ -8,9 +8,12 @@\n>  #pragma once\n>  \n>  #include <functional>\n> +#include <stdint.h>\n>  #include <string>\n>  #include <vector>\n>  \n> +#include <libcamera/base/span.h>\n> +\n>  namespace libcamera {\n>  \n>  namespace utils {\n> @@ -18,6 +21,9 @@ namespace utils {\n>  unsigned int findSharedObjects(const char *libDir, unsigned int maxDepth,\n>                                std::function<int(const std::string &)> func);\n\nReviewed-by: Isaac Scott <isaac.scott@ideasonboard.com>\n\nBest wishes,\nIsaac\n\n>  \n> +int elfVerifyIdent(Span<const uint8_t> elf);\n> +Span<const uint8_t> elfLoadSymbol(Span<const uint8_t> elf, const char *symbol);\n> +\n>  } /* namespace utils */\n>  \n>  } /* namespace libcamera */\n> diff --git a/src/libcamera/ipa_module.cpp b/src/libcamera/ipa_module.cpp\n> index e6ea61e44829..c8559ec8b74c 100644\n> --- a/src/libcamera/ipa_module.cpp\n> +++ b/src/libcamera/ipa_module.cpp\n> @@ -25,6 +25,7 @@\n>  #include <libcamera/base/utils.h>\n>  \n>  #include \"libcamera/internal/pipeline_handler.h\"\n> +#include \"libcamera/internal/utils.h\"\n>  \n>  /**\n>   * \\file ipa_module.h\n> @@ -40,153 +41,6 @@ namespace libcamera {\n>  \n>  LOG_DEFINE_CATEGORY(IPAModule)\n>  \n> -namespace {\n> -\n> -template<typename T>\n> -typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,\n> -                                            off_t offset, size_t objSize)\n> -{\n> -       size_t size = offset + objSize;\n> -       if (size > elf.size() || size < objSize)\n> -               return nullptr;\n> -\n> -       return reinterpret_cast<typename std::remove_extent_t<T> *>(\n> -               reinterpret_cast<const char *>(elf.data()) + offset);\n> -}\n> -\n> -template<typename T>\n> -typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,\n> -                                            off_t offset)\n> -{\n> -       return elfPointer<T>(elf, offset, sizeof(T));\n> -}\n> -\n> -int elfVerifyIdent(Span<const uint8_t> elf)\n> -{\n> -       const char *e_ident = elfPointer<const char[EI_NIDENT]>(elf, 0);\n> -       if (!e_ident)\n> -               return -ENOEXEC;\n> -\n> -       if (e_ident[EI_MAG0] != ELFMAG0 ||\n> -           e_ident[EI_MAG1] != ELFMAG1 ||\n> -           e_ident[EI_MAG2] != ELFMAG2 ||\n> -           e_ident[EI_MAG3] != ELFMAG3 ||\n> -           e_ident[EI_VERSION] != EV_CURRENT)\n> -               return -ENOEXEC;\n> -\n> -       int bitClass = sizeof(unsigned long) == 4 ? ELFCLASS32 : ELFCLASS64;\n> -       if (e_ident[EI_CLASS] != bitClass)\n> -               return -ENOEXEC;\n> -\n> -       int a = 1;\n> -       unsigned char endianness = *reinterpret_cast<char *>(&a) == 1\n> -                                ? ELFDATA2LSB : ELFDATA2MSB;\n> -       if (e_ident[EI_DATA] != endianness)\n> -               return -ENOEXEC;\n> -\n> -       return 0;\n> -}\n> -\n> -const ElfW(Shdr) *elfSection(Span<const uint8_t> elf, const ElfW(Ehdr) *eHdr,\n> -                            ElfW(Half) idx)\n> -{\n> -       if (idx >= eHdr->e_shnum)\n> -               return nullptr;\n> -\n> -       off_t offset = eHdr->e_shoff + idx *\n> -                                      static_cast<uint32_t>(eHdr->e_shentsize);\n> -       return elfPointer<const ElfW(Shdr)>(elf, offset);\n> -}\n> -\n> -/**\n> - * \\brief Retrieve address and size of a symbol from an mmap'ed ELF file\n> - * \\param[in] elf Address and size of mmap'ed ELF file\n> - * \\param[in] symbol Symbol name\n> - *\n> - * \\return The memory region storing the symbol on success, or an empty span\n> - * otherwise\n> - */\n> -Span<const uint8_t> elfLoadSymbol(Span<const uint8_t> elf, const char *symbol)\n> -{\n> -       const ElfW(Ehdr) *eHdr = elfPointer<const ElfW(Ehdr)>(elf, 0);\n> -       if (!eHdr)\n> -               return {};\n> -\n> -       const ElfW(Shdr) *sHdr = elfSection(elf, eHdr, eHdr->e_shstrndx);\n> -       if (!sHdr)\n> -               return {};\n> -       off_t shnameoff = sHdr->sh_offset;\n> -\n> -       /* Locate .dynsym section header. */\n> -       const ElfW(Shdr) *dynsym = nullptr;\n> -       for (unsigned int i = 0; i < eHdr->e_shnum; i++) {\n> -               sHdr = elfSection(elf, eHdr, i);\n> -               if (!sHdr)\n> -                       return {};\n> -\n> -               off_t offset = shnameoff + sHdr->sh_name;\n> -               const char *name = elfPointer<const char[8]>(elf, offset);\n> -               if (!name)\n> -                       return {};\n> -\n> -               if (sHdr->sh_type == SHT_DYNSYM && !strcmp(name, \".dynsym\")) {\n> -                       dynsym = sHdr;\n> -                       break;\n> -               }\n> -       }\n> -\n> -       if (dynsym == nullptr) {\n> -               LOG(IPAModule, Error) << \"ELF has no .dynsym section\";\n> -               return {};\n> -       }\n> -\n> -       sHdr = elfSection(elf, eHdr, dynsym->sh_link);\n> -       if (!sHdr)\n> -               return {};\n> -       off_t dynsym_nameoff = sHdr->sh_offset;\n> -\n> -       /* Locate symbol in the .dynsym section. */\n> -       const ElfW(Sym) *targetSymbol = nullptr;\n> -       unsigned int dynsym_num = dynsym->sh_size / dynsym->sh_entsize;\n> -       for (unsigned int i = 0; i < dynsym_num; i++) {\n> -               off_t offset = dynsym->sh_offset + dynsym->sh_entsize * i;\n> -               const ElfW(Sym) *sym = elfPointer<const ElfW(Sym)>(elf, offset);\n> -               if (!sym)\n> -                       return {};\n> -\n> -               offset = dynsym_nameoff + sym->st_name;\n> -               const char *name = elfPointer<const char>(elf, offset,\n> -                                                         strlen(symbol) + 1);\n> -               if (!name)\n> -                       return {};\n> -\n> -               if (!strcmp(name, symbol) &&\n> -                   sym->st_info & STB_GLOBAL) {\n> -                       targetSymbol = sym;\n> -                       break;\n> -               }\n> -       }\n> -\n> -       if (targetSymbol == nullptr) {\n> -               LOG(IPAModule, Error) << \"Symbol \" << symbol << \" not found\";\n> -               return {};\n> -       }\n> -\n> -       /* Locate and return data of symbol. */\n> -       sHdr = elfSection(elf, eHdr, targetSymbol->st_shndx);\n> -       if (!sHdr)\n> -               return {};\n> -       off_t offset = sHdr->sh_offset + (targetSymbol->st_value - sHdr->sh_addr);\n> -       const uint8_t *data = elfPointer<const uint8_t>(elf, offset,\n> -                                                       targetSymbol->st_size);\n> -       if (!data)\n> -               return {};\n> -\n> -       return { data, targetSymbol->st_size };\n> -}\n> -\n> -} /* namespace */\n> -\n>  /**\n>   * \\def IPA_MODULE_API_VERSION\n>   * \\brief The IPA module API version\n> @@ -280,13 +134,13 @@ int IPAModule::loadIPAModuleInfo()\n>         }\n>  \n>         Span<const uint8_t> data = file.map();\n> -       int ret = elfVerifyIdent(data);\n> +       int ret = utils::elfVerifyIdent(data);\n>         if (ret) {\n>                 LOG(IPAModule, Error) << \"IPA module is not an ELF file\";\n>                 return ret;\n>         }\n>  \n> -       Span<const uint8_t> info = elfLoadSymbol(data, \"ipaModuleInfo\");\n> +       Span<const uint8_t> info = utils::elfLoadSymbol(data, \"ipaModuleInfo\");\n>         if (info.size() < sizeof(info_)) {\n>                 LOG(IPAModule, Error) << \"IPA module has no valid info\";\n>                 return -EINVAL;\n> diff --git a/src/libcamera/utils.cpp b/src/libcamera/utils.cpp\n> index 2ce62f236cea..6894b489b557 100644\n> --- a/src/libcamera/utils.cpp\n> +++ b/src/libcamera/utils.cpp\n> @@ -10,20 +10,63 @@\n>  #include <algorithm>\n>  #include <dirent.h>\n>  #include <functional>\n> +#include <link.h>\n> +#include <stdint.h>\n>  #include <string.h>\n>  #include <string>\n>  #include <sys/types.h>\n>  #include <vector>\n>  \n> +#include <libcamera/base/log.h>\n> +\n>  /**\n>   * \\file internal/utils.h\n>   * \\brief Miscellaneous utility functions (internal)\n>   */\n>  \n> +/* musl doesn't declare _DYNAMIC in link.h, declare it manually. */\n> +extern ElfW(Dyn) _DYNAMIC[];\n> +\n>  namespace libcamera {\n>  \n> +namespace {\n> +\n> +template<typename T>\n> +typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,\n> +                                            off_t offset, size_t objSize)\n> +{\n> +       size_t size = offset + objSize;\n> +       if (size > elf.size() || size < objSize)\n> +               return nullptr;\n> +\n> +       return reinterpret_cast<typename std::remove_extent_t<T> *>(\n> +               reinterpret_cast<const char *>(elf.data()) + offset);\n> +}\n> +\n> +template<typename T>\n> +typename std::remove_extent_t<T> *elfPointer(Span<const uint8_t> elf,\n> +                                            off_t offset)\n> +{\n> +       return elfPointer<T>(elf, offset, sizeof(T));\n> +}\n> +\n> +const ElfW(Shdr) *elfSection(Span<const uint8_t> elf, const ElfW(Ehdr) *eHdr,\n> +                            ElfW(Half) idx)\n> +{\n> +       if (idx >= eHdr->e_shnum)\n> +               return nullptr;\n> +\n> +       off_t offset = eHdr->e_shoff + idx *\n> +                                      static_cast<uint32_t>(eHdr->e_shentsize);\n> +       return elfPointer<const ElfW(Shdr)>(elf, offset);\n> +}\n> +\n> +} /* namespace */\n> +\n>  namespace utils {\n>  \n> +LOG_DEFINE_CATEGORY(Utils)\n> +\n>  /**\n>   * \\brief Identify shared library objects within a directory\n>   * \\param[in] libDir The directory to search for shared objects\n> @@ -102,6 +145,125 @@ unsigned int findSharedObjects(const char *libDir, unsigned int maxDepth,\n>         return count;\n>  }\n>  \n> +/**\n> + * \\brief Verify that a binary blob is an ELF\n> + * \\param[in] elf The binary blob as a Span\n> + *\n> + * \\return 0 for success, and -ENOEXEC otherwise\n> + */\n> +int elfVerifyIdent(Span<const uint8_t> elf)\n> +{\n> +       const char *e_ident = elfPointer<const char[EI_NIDENT]>(elf, 0);\n> +       if (!e_ident)\n> +               return -ENOEXEC;\n> +\n> +       if (e_ident[EI_MAG0] != ELFMAG0 ||\n> +           e_ident[EI_MAG1] != ELFMAG1 ||\n> +           e_ident[EI_MAG2] != ELFMAG2 ||\n> +           e_ident[EI_MAG3] != ELFMAG3 ||\n> +           e_ident[EI_VERSION] != EV_CURRENT)\n> +               return -ENOEXEC;\n> +\n> +       int bitClass = sizeof(unsigned long) == 4 ? ELFCLASS32 : ELFCLASS64;\n> +       if (e_ident[EI_CLASS] != bitClass)\n> +               return -ENOEXEC;\n> +\n> +       int a = 1;\n> +       unsigned char endianness = *reinterpret_cast<char *>(&a) == 1\n> +                                ? ELFDATA2LSB : ELFDATA2MSB;\n> +       if (e_ident[EI_DATA] != endianness)\n> +               return -ENOEXEC;\n> +\n> +       return 0;\n> +}\n> +\n> +/**\n> + * \\brief Retrieve address and size of a symbol from an mmap'ed ELF file\n> + * \\param[in] elf Address and size of mmap'ed ELF file\n> + * \\param[in] symbol Symbol name\n> + *\n> + * \\return The memory region storing the symbol on success, or an empty span\n> + * otherwise\n> + */\n> +Span<const uint8_t> elfLoadSymbol(Span<const uint8_t> elf, const char *symbol)\n> +{\n> +       const ElfW(Ehdr) *eHdr = elfPointer<const ElfW(Ehdr)>(elf, 0);\n> +       if (!eHdr)\n> +               return {};\n> +\n> +       const ElfW(Shdr) *sHdr = elfSection(elf, eHdr, eHdr->e_shstrndx);\n> +       if (!sHdr)\n> +               return {};\n> +       off_t shnameoff = sHdr->sh_offset;\n> +\n> +       /* Locate .dynsym section header. */\n> +       const ElfW(Shdr) *dynsym = nullptr;\n> +       for (unsigned int i = 0; i < eHdr->e_shnum; i++) {\n> +               sHdr = elfSection(elf, eHdr, i);\n> +               if (!sHdr)\n> +                       return {};\n> +\n> +               off_t offset = shnameoff + sHdr->sh_name;\n> +               const char *name = elfPointer<const char[8]>(elf, offset);\n> +               if (!name)\n> +                       return {};\n> +\n> +               if (sHdr->sh_type == SHT_DYNSYM && !strcmp(name, \".dynsym\")) {\n> +                       dynsym = sHdr;\n> +                       break;\n> +               }\n> +       }\n> +\n> +       if (dynsym == nullptr) {\n> +               LOG(Utils, Error) << \"ELF has no .dynsym section\";\n> +               return {};\n> +       }\n> +\n> +       sHdr = elfSection(elf, eHdr, dynsym->sh_link);\n> +       if (!sHdr)\n> +               return {};\n> +       off_t dynsym_nameoff = sHdr->sh_offset;\n> +\n> +       /* Locate symbol in the .dynsym section. */\n> +       const ElfW(Sym) *targetSymbol = nullptr;\n> +       unsigned int dynsym_num = dynsym->sh_size / dynsym->sh_entsize;\n> +       for (unsigned int i = 0; i < dynsym_num; i++) {\n> +               off_t offset = dynsym->sh_offset + dynsym->sh_entsize * i;\n> +               const ElfW(Sym) *sym = elfPointer<const ElfW(Sym)>(elf, offset);\n> +               if (!sym)\n> +                       return {};\n> +\n> +               offset = dynsym_nameoff + sym->st_name;\n> +               const char *name = elfPointer<const char>(elf, offset,\n> +                                                         strlen(symbol) + 1);\n> +               if (!name)\n> +                       return {};\n> +\n> +               if (!strcmp(name, symbol) &&\n> +                   sym->st_info & STB_GLOBAL) {\n> +                       targetSymbol = sym;\n> +                       break;\n> +               }\n> +       }\n> +\n> +       if (targetSymbol == nullptr) {\n> +               LOG(Utils, Error) << \"Symbol \" << symbol << \" not found\";\n> +               return {};\n> +       }\n> +\n> +       /* Locate and return data of symbol. */\n> +       sHdr = elfSection(elf, eHdr, targetSymbol->st_shndx);\n> +       if (!sHdr)\n> +               return {};\n> +       off_t offset = sHdr->sh_offset + (targetSymbol->st_value - sHdr->sh_addr);\n> +       const uint8_t *data = elfPointer<const uint8_t>(elf, offset,\n> +                                                       targetSymbol->st_size);\n> +       if (!data)\n> +               return {};\n> +\n> +       return { data, targetSymbol->st_size };\n> +}\n> +\n>  } /* namespace utils */\n>  \n>  } /* namespace libcamera */\n> -- \n> 2.47.2\n>","headers":{"Return-Path":"<libcamera-devel-bounces@lists.libcamera.org>","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 8DE77BE175\n\tfor <parsemail@patchwork.libcamera.org>;\n\tTue, 24 Feb 2026 11:13:08 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id BA95562294;\n\tTue, 24 Feb 2026 12:13:07 +0100 (CET)","from perceval.ideasonboard.com (perceval.ideasonboard.com\n\t[IPv6:2001:4b98:dc2:55:216:3eff:fef7:d647])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id E2C3562080\n\tfor <libcamera-devel@lists.libcamera.org>;\n\tTue, 24 Feb 2026 12:13:05 +0100 (CET)","from thinkpad.ideasonboard.com\n\t(cpc89244-aztw30-2-0-cust6594.18-1.cable.virginm.net [86.31.185.195])\n\tby perceval.ideasonboard.com (Postfix) with ESMTPSA id F3C75AB4;\n\tTue, 24 Feb 2026 12:12:08 +0100 (CET)"],"Authentication-Results":"lancelot.ideasonboard.com; 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