diff options
Diffstat (limited to 'pkgs/development/tools/misc/saleae-logic/preload.c')
-rw-r--r-- | pkgs/development/tools/misc/saleae-logic/preload.c | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/pkgs/development/tools/misc/saleae-logic/preload.c b/pkgs/development/tools/misc/saleae-logic/preload.c new file mode 100644 index 00000000000..6b3632db97b --- /dev/null +++ b/pkgs/development/tools/misc/saleae-logic/preload.c @@ -0,0 +1,114 @@ +/* + * LD_PRELOAD trick to make Saleae Logic work from a read-only installation + * directory. + * + * Saleae Logic tries to write to the ./Settings/settings.xml file, relative to + * its installation directory. Because the nix store is read-only, we have to + * redirect access to this file somewhere else. Here's the map: + * + * $out/Settings/settings.xml => $HOME/.saleae-logic-settings.xml + * + * This also makes the software multi-user aware :-) + * + * NOTE: The next Logic version is supposed to have command line parameters for + * configuring where the Settings/ directory is located, but until then we have + * to use this. + * + * Usage: + * gcc -shared -fPIC -DOUT="$out" preload.c -o preload.so -ldl + * LD_PRELOAD=$PWD/preload.so ./result/Logic + * + * To see the paths that are modified at runtime, set the environment variable + * PRELOAD_DEBUG to 1 (or anything really; debugging is on as long as the + * variable exists). + */ + +#define _GNU_SOURCE +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <fcntl.h> +#include <dlfcn.h> +#include <limits.h> +#include <sys/stat.h> +#include <sys/types.h> + +#ifndef OUT +#error Missing OUT define - path to the installation directory. +#endif + +typedef FILE *(*fopen_func_t)(const char *path, const char *mode); +typedef FILE *(*fopen64_func_t)(const char *path, const char *mode); + +/* + * Redirect $out/Settings/settings.xml => $HOME/.saleae-logic-settings.xml. No + * other paths are changed. Path is truncated if bigger than PATH_MAX. + * + * @param pathname Original file path. + * @param buffer Pointer to a buffer of size PATH_MAX bytes that this function + * will write the new redirected path to (if needed). + * + * @return Pointer to the resulting path. It will either be equal to the + * pathname or buffer argument. + */ +static const char *redirect(const char *pathname, char *buffer) +{ + const char *homepath; + const char *new_path; + static char have_warned; + + homepath = getenv("HOME"); + if (!homepath) { + homepath = "/"; + if (!have_warned && getenv("PRELOAD_DEBUG")) { + fprintf(stderr, "preload_debug: WARNING: HOME is unset, using \"/\" (root) instead.\n"); + have_warned = 1; + } + } + + new_path = pathname; + if (strcmp(OUT "/Settings/settings.xml", pathname) == 0) { + snprintf(buffer, PATH_MAX, "%s/.saleae-logic-settings.xml", homepath); + buffer[PATH_MAX-1] = '\0'; + new_path = buffer; + } + + return new_path; +} + +FILE *fopen(const char *pathname, const char *mode) +{ + FILE *fp; + const char *path; + char buffer[PATH_MAX]; + fopen_func_t orig_fopen; + + orig_fopen = (fopen_func_t)dlsym(RTLD_NEXT, "fopen"); + path = redirect(pathname, buffer); + fp = orig_fopen(path, mode); + + if (path != pathname && getenv("PRELOAD_DEBUG")) { + fprintf(stderr, "preload_debug: fopen(\"%s\", \"%s\") => \"%s\": fp=%p\n", pathname, mode, path, fp); + } + + return fp; +} + +FILE *fopen64(const char *pathname, const char *mode) +{ + FILE *fp; + const char *path; + char buffer[PATH_MAX]; + fopen64_func_t orig_fopen64; + + orig_fopen64 = (fopen64_func_t)dlsym(RTLD_NEXT, "fopen64"); + path = redirect(pathname, buffer); + fp = orig_fopen64(path, mode); + + if (path != pathname && getenv("PRELOAD_DEBUG")) { + fprintf(stderr, "preload_debug: fopen64(\"%s\", \"%s\") => \"%s\": fp=%p\n", pathname, mode, path, fp); + } + + return fp; +} |