From 39f39b5568c34b2b40681cdb021c04cd6ae3bbef Mon Sep 17 00:00:00 2001 From: Robert Scott Date: Wed, 5 Jun 2024 23:09:12 +0100 Subject: [PATCH] doc/stdenv: hardening flags: add section on zerocallusedregs --- doc/stdenv/stdenv.chapter.md | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/doc/stdenv/stdenv.chapter.md b/doc/stdenv/stdenv.chapter.md index a331ceb689ec..93ddeff7d016 100644 --- a/doc/stdenv/stdenv.chapter.md +++ b/doc/stdenv/stdenv.chapter.md @@ -1667,6 +1667,10 @@ Adds the `-fPIE` compiler and `-pie` linker options. Position Independent Execut Static libraries need to be compiled with `-fPIE` so that executables can link them in with the `-pie` linker option. If the libraries lack `-fPIE`, you will get the error `recompile with -fPIE`. +#### `zerocallusedregs` {#zerocallusedregs} + +Adds the `-fzero-call-used-regs=used-gpr` compiler option. This causes the general-purpose registers that an architecture's calling convention considers "call-used" to be zeroed on return from the function. This can make it harder for attackers to construct useful ROP gadgets and also reduces the chance of data leakage from a function call. + [^footnote-stdenv-ignored-build-platform]: The build platform is ignored because it is a mere implementation detail of the package satisfying the dependency: As a general programming principle, dependencies are always *specified* as interfaces, not concrete implementation. [^footnote-stdenv-native-dependencies-in-path]: Currently, this means for native builds all dependencies are put on the `PATH`. But in the future that may not be the case for sake of matching cross: the platforms would be assumed to be unique for native and cross builds alike, so only the `depsBuild*` and `nativeBuildInputs` would be added to the `PATH`. [^footnote-stdenv-propagated-dependencies]: Nix itself already takes a package’s transitive dependencies into account, but this propagation ensures nixpkgs-specific infrastructure like [setup hooks](#ssec-setup-hooks) also are run as if it were a propagated dependency.