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author | 0x4A6F <0x4A6F@users.noreply.github.com> | 2022-01-06 19:21:47 +0100 |
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committer | GitHub <noreply@github.com> | 2022-01-06 19:21:47 +0100 |
commit | 29acc14f0db8957855c1e629a105992a4c975100 (patch) | |
tree | 7980af52690dc26b93263efcfa53d18253cdf858 /pkgs/applications/virtualization/qemu | |
parent | 7a022212c83000b4d56d93df4cd5610caa74e4b9 (diff) | |
parent | c8d137961d29b7ad1e9470718802209b0e636776 (diff) |
Merge pull request #143060 from zhaofengli/binfmt-argv0
nixos/binfmt: Add QEMU wrapper to preserve argv[0]
Diffstat (limited to 'pkgs/applications/virtualization/qemu')
-rw-r--r-- | pkgs/applications/virtualization/qemu/binfmt-p-wrapper.c | 79 | ||||
-rw-r--r-- | pkgs/applications/virtualization/qemu/binfmt-p-wrapper.nix | 31 |
2 files changed, 110 insertions, 0 deletions
diff --git a/pkgs/applications/virtualization/qemu/binfmt-p-wrapper.c b/pkgs/applications/virtualization/qemu/binfmt-p-wrapper.c new file mode 100644 index 0000000000000..f956768862eca --- /dev/null +++ b/pkgs/applications/virtualization/qemu/binfmt-p-wrapper.c @@ -0,0 +1,79 @@ +// This is a tiny wrapper that converts the extra arv[0] argument +// from binfmt-misc with the P flag enabled to QEMU parameters. +// It also prevents LD_* environment variables from being applied +// to QEMU itself. + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#ifndef TARGET_QEMU +#error "Define TARGET_QEMU to be the path to the qemu-user binary (e.g., -DTARGET_QEMU=\"/full/path/to/qemu-riscv64\")" +#endif + +extern char **environ; + +int main(int argc, char *argv[]) { + if (argc < 3) { + fprintf(stderr, "%s: This should be run as the binfmt interpreter with the P flag\n", argv[0]); + fprintf(stderr, "%s: My preconfigured qemu-user binary: %s\n", argv[0], TARGET_QEMU); + return 1; + } + + size_t environ_count = 0; + for (char **cur = environ; *cur != NULL; ++cur) { + environ_count++; + } + + size_t new_argc = 3; + size_t new_argv_alloc = argc + 2 * environ_count + 2; // [ "-E", env ] for each LD_* env + [ "-0", argv0 ] + char **new_argv = (char**)malloc((new_argv_alloc + 1) * sizeof(char*)); + if (!new_argv) { + fprintf(stderr, "FATAL: Failed to allocate new argv array\n"); + abort(); + } + + new_argv[0] = TARGET_QEMU; + new_argv[1] = "-0"; + new_argv[2] = argv[2]; + + // Pass all LD_ env variables as -E and strip them in `new_environ` + size_t new_environc = 0; + char **new_environ = (char**)malloc((environ_count + 1) * sizeof(char*)); + if (!new_environ) { + fprintf(stderr, "FATAL: Failed to allocate new environ array\n"); + abort(); + } + + for (char **cur = environ; *cur != NULL; ++cur) { + if (strncmp("LD_", *cur, 3) == 0) { + new_argv[new_argc++] = "-E"; + new_argv[new_argc++] = *cur; + } else { + new_environ[new_environc++] = *cur; + } + } + new_environ[new_environc] = NULL; + + size_t new_arg_start = new_argc; + new_argc += argc - 3 + 2; // [ "--", full_binary_path ] + + if (argc > 3) { + memcpy(&new_argv[new_arg_start + 2], &argv[3], (argc - 3) * sizeof(char**)); + } + + new_argv[new_arg_start] = "--"; + new_argv[new_arg_start + 1] = argv[1]; + new_argv[new_argc] = NULL; + +#ifdef DEBUG + for (size_t i = 0; i < new_argc; ++i) { + fprintf(stderr, "argv[%zu] = %s\n", i, new_argv[i]); + } +#endif + + return execve(new_argv[0], new_argv, new_environ); +} + +// vim: et:ts=4:sw=4 diff --git a/pkgs/applications/virtualization/qemu/binfmt-p-wrapper.nix b/pkgs/applications/virtualization/qemu/binfmt-p-wrapper.nix new file mode 100644 index 0000000000000..fada14569299b --- /dev/null +++ b/pkgs/applications/virtualization/qemu/binfmt-p-wrapper.nix @@ -0,0 +1,31 @@ +# binfmt preserve-argv[0] wrapper +# +# More details in binfmt-p-wrapper.c +# +# The wrapper has to be static so LD_* environment variables +# cannot affect the execution of the wrapper itself. + +{ lib, stdenv, pkgsStatic, enableDebug ? false }: + +name: emulator: + +pkgsStatic.stdenv.mkDerivation { + inherit name; + + src = ./binfmt-p-wrapper.c; + + dontUnpack = true; + dontInstall = true; + + buildPhase = '' + runHook preBuild + + mkdir -p $out/bin + $CC -o $out/bin/${name} -static -std=c99 -O2 \ + -DTARGET_QEMU=\"${emulator}\" \ + ${lib.optionalString enableDebug "-DDEBUG"} \ + $src + + runHook postBuild + ''; +} |