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a=openpgp; fpr=35CCFB63B283D6D3AEB783944CB5F6848BBC56EE X-Developer-Signature: v=1; a=openpgp-sha256; l=2005; i=samitolvanen@google.com; h=from:subject; bh=u2NAoGPKAPKT+TpiqoFdPon2GiyhMXZdDU3h7zflpd4=; b=owEB7QES/pANAwAKAUy19oSLvFbuAcsmYgBmvj06nYnAUNx8o66EBLX4cU2eInAJSpLP8qYpz sKtbF+ZNs+JAbMEAAEKAB0WIQQ1zPtjsoPW0663g5RMtfaEi7xW7gUCZr49OgAKCRBMtfaEi7xW 7h06DACM546WdYBdw7Q9mrV/mD1RWAUpswtCJqVQxJ1f5GKGao7eEcXupGQuIPnw5Ey1+gEthL/ zUx8fmz4IOOWvMPnn54qc/0OYW6/yOLHQwIOrDeJJf1hMUgHTEdAad87xgKJCve78B3TGIfh2nK 0yG7q7yEEOxwnfzUWqETFg86JLzNqDLEcF+Le7QPYIg1crSXxPSGj6Qiq+dIClVReWIE6CEXm6A jWmn1/KCkWAGpc279+B+yrNNeukRQIgxYLJ88G+cLlgO31F4vU6302m5gBkhobfa5+qVTq3iPBi l2Qpx22OOHSDBGGwUufoz7aw+kwon3jhDBACj7QQTb+EJlImWNzKGwUtNj/9Meh0Z3Xr4ZEiquw A0WEfBnHtAuLfLpMfn2gsfq/4/5XA4sjbgrBgGBx5xR+Oa1fZwoL0dsfPIBqAXw9LoxbFAMytxK plh5XkQf3fItnk4E4Zyj5I8eM3vUaUZ4Mr52o+5/5O182vI0Y8C1VVTNzQiI1HDbrRaK8= X-Mailer: git-send-email 2.46.0.184.g6999bdac58-goog Message-ID: <20240815173903.4172139-38-samitolvanen@google.com> Subject: [PATCH v2 17/19] export: Add __gendwarfksyms_ptr_ references to exported symbols From: Sami Tolvanen To: Masahiro Yamada , Luis Chamberlain , Miguel Ojeda , Greg Kroah-Hartman Cc: Matthew Maurer , Alex Gaynor , Wedson Almeida Filho , Gary Guo , Petr Pavlu , Neal Gompa , Hector Martin , Janne Grunau , Asahi Linux , linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, linux-modules@vger.kernel.org, rust-for-linux@vger.kernel.org, Sami Tolvanen With gendwarfksyms, we need each TU where the EXPORT_SYMBOL() macro is used to also contain DWARF type information for the symbols it exports. However, as a TU can also export external symbols and compilers may choose not to emit debugging information for symbols not defined in the current TU, the missing types will result in missing symbol versions. Stand-alone assembly code also doesn't contain type information for exported symbols, so we need to compile a temporary object file with asm-prototypes.h instead, and similarly need to ensure the DWARF in the temporary object file contains the necessary types. To always emit type information for external exports, add explicit __gendwarfksyms_ptr_ references to them in EXPORT_SYMBOL(). gendwarfksyms will use the type information for __gendwarfksyms_ptr_* if needed. Discard the pointers from the final binary to avoid further bloat. Signed-off-by: Sami Tolvanen --- include/linux/export.h | 15 +++++++++++++++ 1 file changed, 15 insertions(+) diff --git a/include/linux/export.h b/include/linux/export.h index 0bbd02fd351d..cf71d3202e5b 100644 --- a/include/linux/export.h +++ b/include/linux/export.h @@ -52,9 +52,24 @@ #else +#ifdef CONFIG_GENDWARFKSYMS +/* + * With CONFIG_GENDWARFKSYMS, ensure the compiler emits debugging + * information for all exported symbols, including those defined in + * different TUs, by adding a __gendwarfksyms_ptr_ pointer + * that's discarded during the final link. + */ +#define __GENDWARFKSYMS_EXPORT(sym) \ + static typeof(sym) *__gendwarfksyms_ptr_##sym __used \ + __section(".discard.gendwarfksyms") = &sym; +#else +#define __GENDWARFKSYMS_EXPORT(sym) +#endif + #define __EXPORT_SYMBOL(sym, license, ns) \ extern typeof(sym) sym; \ __ADDRESSABLE(sym) \ + __GENDWARFKSYMS_EXPORT(sym) \ asm(__stringify(___EXPORT_SYMBOL(sym, license, ns))) #endif