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Re: [Qemu-devel] [PATCH] linux-user: Add generic env variable handling


From: Aurelien Jarno
Subject: Re: [Qemu-devel] [PATCH] linux-user: Add generic env variable handling
Date: Fri, 30 Jan 2009 20:52:15 +0100
User-agent: Mutt/1.5.18 (2008-05-17)

On Mon, Jan 19, 2009 at 05:30:15PM +0200, Riku Voipio wrote:
> Adds support for qemu to modify target process environment
> variables using -E and -U commandline switches. This replaces
> eventually the -drop-ld-preload flag.
> 
> From: Mika Westerberg
> 
> Signed-off-by: Riku Voipio <address@hidden>
> ---

Thanks, applied.

>  Makefile.target      |    2 +-
>  linux-user/envlist.c |  247 
> ++++++++++++++++++++++++++++++++++++++++++++++++++
>  linux-user/envlist.h |   22 +++++
>  linux-user/main.c    |   50 +++++++---
>  4 files changed, 304 insertions(+), 17 deletions(-)
>  create mode 100644 linux-user/envlist.c
>  create mode 100644 linux-user/envlist.h
> 
> diff --git a/Makefile.target b/Makefile.target
> index fcaf4ec..a736343 100644
> --- a/Makefile.target
> +++ b/Makefile.target
> @@ -373,7 +373,7 @@ CFLAGS+=-p
>  endif
>  
>  OBJS= main.o syscall.o strace.o mmap.o signal.o path.o thunk.o \
> -      elfload.o linuxload.o uaccess.o
> +      elfload.o linuxload.o uaccess.o envlist.o
>  LIBS+= $(AIOLIBS)
>  ifdef TARGET_HAS_BFLT
>  OBJS+= flatload.o
> diff --git a/linux-user/envlist.c b/linux-user/envlist.c
> new file mode 100644
> index 0000000..e13c2d3
> --- /dev/null
> +++ b/linux-user/envlist.c
> @@ -0,0 +1,247 @@
> +#include <sys/queue.h>
> +
> +#include <assert.h>
> +#include <errno.h>
> +#include <stdlib.h>
> +#include <string.h>
> +#include <unistd.h>
> +
> +#include "envlist.h"
> +
> +struct envlist_entry {
> +     const char *ev_var;                     /* actual env value */
> +     LIST_ENTRY(envlist_entry) ev_link;
> +};
> +
> +struct envlist {
> +     LIST_HEAD(, envlist_entry) el_entries;  /* actual entries */
> +     size_t el_count;                        /* number of entries */
> +};
> +
> +static int envlist_parse(envlist_t *envlist,
> +    const char *env, int (*)(envlist_t *, const char *));
> +
> +/*
> + * Allocates new envlist and returns pointer to that or
> + * NULL in case of error.
> + */
> +envlist_t *
> +envlist_create(void)
> +{
> +     envlist_t *envlist;
> +
> +     if ((envlist = malloc(sizeof (*envlist))) == NULL)
> +             return (NULL);
> +
> +     LIST_INIT(&envlist->el_entries);
> +     envlist->el_count = 0;
> +
> +     return (envlist);
> +}
> +
> +/*
> + * Releases given envlist and its entries.
> + */
> +void
> +envlist_free(envlist_t *envlist)
> +{
> +     struct envlist_entry *entry;
> +
> +     assert(envlist != NULL);
> +
> +     while (envlist->el_entries.lh_first != NULL) {
> +             entry = envlist->el_entries.lh_first;
> +             LIST_REMOVE(entry, ev_link);
> +
> +             free((char *)entry->ev_var);
> +             free(entry);
> +     }
> +     free(envlist);
> +}
> +
> +/*
> + * Parses comma separated list of set/modify environment
> + * variable entries and updates given enlist accordingly.
> + *
> + * For example:
> + *     envlist_parse(el, "HOME=foo,SHELL=/bin/sh");
> + *
> + * inserts/sets environment variables HOME and SHELL.
> + *
> + * Returns 0 on success, errno otherwise.
> + */
> +int
> +envlist_parse_set(envlist_t *envlist, const char *env)
> +{
> +     return (envlist_parse(envlist, env, &envlist_setenv));
> +}
> +
> +/*
> + * Parses comma separated list of unset environment variable
> + * entries and removes given variables from given envlist.
> + *
> + * Returns 0 on success, errno otherwise.
> + */
> +int
> +envlist_parse_unset(envlist_t *envlist, const char *env)
> +{
> +     return (envlist_parse(envlist, env, &envlist_unsetenv));
> +}
> +
> +/*
> + * Parses comma separated list of set, modify or unset entries
> + * and calls given callback for each entry.
> + *
> + * Returns 0 in case of success, errno otherwise.
> + */
> +static int
> +envlist_parse(envlist_t *envlist, const char *env,
> +    int (*callback)(envlist_t *, const char *))
> +{
> +     char *tmpenv, *envvar;
> +     char *envsave = NULL;
> +
> +     assert(callback != NULL);
> +
> +     if ((envlist == NULL) || (env == NULL))
> +             return (EINVAL);
> +
> +     /*
> +      * We need to make temporary copy of the env string
> +      * as strtok_r(3) modifies it while it tokenizes.
> +      */
> +     if ((tmpenv = strdup(env)) == NULL)
> +             return (errno);
> +
> +     envvar = strtok_r(tmpenv, ",", &envsave);
> +     while (envvar != NULL) {
> +             if ((*callback)(envlist, envvar) != 0) {
> +                     free(tmpenv);
> +                     return (errno);
> +             }
> +             envvar = strtok_r(NULL, ",", &envsave);
> +     }
> +
> +     free(tmpenv);
> +     return (0);
> +}
> +
> +/*
> + * Sets environment value to envlist in similar manner
> + * than putenv(3).
> + *
> + * Returns 0 in success, errno otherwise.
> + */
> +int
> +envlist_setenv(envlist_t *envlist, const char *env)
> +{
> +     struct envlist_entry *entry = NULL;
> +     const char *eq_sign;
> +     size_t envname_len;
> +
> +     if ((envlist == NULL) || (env == NULL))
> +             return (EINVAL);
> +
> +     /* find out first equals sign in given env */
> +     if ((eq_sign = strchr(env, '=')) == NULL)
> +             return (EINVAL);
> +     envname_len = eq_sign - env + 1;
> +
> +     /*
> +      * If there already exists variable with given name
> +      * we remove and release it before allocating a whole
> +      * new entry.
> +      */
> +     for (entry = envlist->el_entries.lh_first; entry != NULL;
> +         entry = entry->ev_link.le_next) {
> +             if (strncmp(entry->ev_var, env, envname_len) == 0)
> +                     break;
> +     }
> +
> +     if (entry != NULL) {
> +             LIST_REMOVE(entry, ev_link);
> +             free((char *)entry->ev_var);
> +             free(entry);
> +     } else {
> +             envlist->el_count++;
> +     }
> +
> +     if ((entry = malloc(sizeof (*entry))) == NULL)
> +             return (errno);
> +     if ((entry->ev_var = strdup(env)) == NULL) {
> +             free(entry);
> +             return (errno);
> +     }
> +     LIST_INSERT_HEAD(&envlist->el_entries, entry, ev_link);
> +
> +     return (0);
> +}
> +
> +/*
> + * Removes given env value from envlist in similar manner
> + * than unsetenv(3).  Returns 0 in success, errno otherwise.
> + */
> +int
> +envlist_unsetenv(envlist_t *envlist, const char *env)
> +{
> +     struct envlist_entry *entry;
> +     size_t envname_len;
> +
> +     if ((envlist == NULL) || (env == NULL))
> +             return (EINVAL);
> +
> +     /* env is not allowed to contain '=' */
> +     if (strchr(env, '=') != NULL)
> +             return (EINVAL);
> +
> +     /*
> +      * Find out the requested entry and remove
> +      * it from the list.
> +      */
> +     envname_len = strlen(env);
> +     for (entry = envlist->el_entries.lh_first; entry != NULL;
> +         entry = entry->ev_link.le_next) {
> +             if (strncmp(entry->ev_var, env, envname_len) == 0)
> +                     break;
> +     }
> +     if (entry != NULL) {
> +             LIST_REMOVE(entry, ev_link);
> +             free((char *)entry->ev_var);
> +             free(entry);
> +
> +             envlist->el_count--;
> +     }
> +     return (0);
> +}
> +
> +/*
> + * Returns given envlist as array of strings (in same form that
> + * global variable environ is).  Caller must free returned memory
> + * by calling free(3) for each element and for the array.  Returned
> + * array and given envlist are not related (no common references).
> + *
> + * If caller provides count pointer, number of items in array is
> + * stored there.  In case of error, NULL is returned and no memory
> + * is allocated.
> + */
> +char **
> +envlist_to_environ(const envlist_t *envlist, size_t *count)
> +{
> +     struct envlist_entry *entry;
> +     char **env, **penv;
> +
> +     penv = env = malloc((envlist->el_count + 1) * sizeof (char *));
> +     if (env == NULL)
> +             return (NULL);
> +
> +     for (entry = envlist->el_entries.lh_first; entry != NULL;
> +         entry = entry->ev_link.le_next) {
> +             *(penv++) = strdup(entry->ev_var);
> +     }
> +     *penv = NULL; /* NULL terminate the list */
> +
> +     if (count != NULL)
> +             *count = envlist->el_count;
> +
> +     return (env);
> +}
> diff --git a/linux-user/envlist.h b/linux-user/envlist.h
> new file mode 100644
> index 0000000..e76d4a1
> --- /dev/null
> +++ b/linux-user/envlist.h
> @@ -0,0 +1,22 @@
> +#ifndef ENVLIST_H
> +#define ENVLIST_H
> +
> +#ifdef __cplusplus
> +extern "C" {
> +#endif
> +
> +typedef struct envlist envlist_t;
> +
> +extern       envlist_t *envlist_create(void);
> +extern       void envlist_free(envlist_t *);
> +extern       int envlist_setenv(envlist_t *, const char *);
> +extern       int envlist_unsetenv(envlist_t *, const char *);
> +extern       int envlist_parse_set(envlist_t *, const char *);
> +extern       int envlist_parse_unset(envlist_t *, const char *);
> +extern       char **envlist_to_environ(const envlist_t *, size_t *);
> +
> +#ifdef __cplusplus
> +}
> +#endif
> +
> +#endif /* ENVLIST_H */
> diff --git a/linux-user/main.c b/linux-user/main.c
> index 2ffe244..21a0626 100644
> --- a/linux-user/main.c
> +++ b/linux-user/main.c
> @@ -32,6 +32,9 @@
>  /* For tb_lock */
>  #include "exec-all.h"
>  
> +
> +#include "envlist.h"
> +
>  #define DEBUG_LOGFILE "/tmp/qemu.log"
>  
>  char *exec_path;
> @@ -2190,6 +2193,8 @@ static void usage(void)
>             "-s size           set the stack size in bytes (default=%ld)\n"
>             "-cpu model        select CPU (-cpu ? for list)\n"
>             "-drop-ld-preload  drop LD_PRELOAD for target process\n"
> +           "-E var=value      sets/modifies targets environment 
> variable(s)\n"
> +           "-U var            unsets targets environment variable(s)\n"
>             "\n"
>             "Debug options:\n"
>             "-d options   activate log (logfile=%s)\n"
> @@ -2199,6 +2204,12 @@ static void usage(void)
>             "Environment variables:\n"
>             "QEMU_STRACE       Print system calls and arguments similar to 
> the\n"
>             "                  'strace' program.  Enable by setting to any 
> value.\n"
> +           "You can use -E and -U options to set/unset environment 
> variables\n"
> +           "for target process.  It is possible to provide several 
> variables\n"
> +           "by repeating the option.  For example:\n"
> +           "    -E var1=val2 -E var2=val2 -U LD_PRELOAD -U LD_DEBUG\n"
> +           "Note that if you provide several changes to single variable\n"
> +           "last change will stay in effect.\n"
>             ,
>             TARGET_ARCH,
>             interp_prefix,
> @@ -2233,8 +2244,8 @@ int main(int argc, char **argv, char **envp)
>      int optind;
>      const char *r;
>      int gdbstub_port = 0;
> -    int drop_ld_preload = 0, environ_count = 0;
> -    char **target_environ, **wrk, **dst;
> +    char **target_environ, **wrk;
> +    envlist_t *envlist = NULL;
>  
>      if (argc <= 1)
>          usage();
> @@ -2244,6 +2255,16 @@ int main(int argc, char **argv, char **envp)
>      /* init debug */
>      cpu_set_log_filename(DEBUG_LOGFILE);
>  
> +    if ((envlist = envlist_create()) == NULL) {
> +        (void) fprintf(stderr, "Unable to allocate envlist\n");
> +        exit(1);
> +    }
> +
> +    /* add current environment into the list */
> +    for (wrk = environ; *wrk != NULL; wrk++) {
> +        (void) envlist_setenv(envlist, *wrk);
> +    }
> +
>      cpu_model = NULL;
>      optind = 1;
>      for(;;) {
> @@ -2273,6 +2294,14 @@ int main(int argc, char **argv, char **envp)
>                  _exit(1);
>              }
>              cpu_set_log(mask);
> +        } else if (!strcmp(r, "E")) {
> +            r = argv[optind++];
> +            if (envlist_setenv(envlist, r) != 0)
> +                usage();
> +        } else if (!strcmp(r, "U")) {
> +            r = argv[optind++];
> +            if (envlist_unsetenv(envlist, r) != 0)
> +                usage();
>          } else if (!strcmp(r, "s")) {
>              r = argv[optind++];
>              x86_stack_size = strtol(r, (char **)&r, 0);
> @@ -2305,7 +2334,7 @@ int main(int argc, char **argv, char **envp)
>                  _exit(1);
>              }
>          } else if (!strcmp(r, "drop-ld-preload")) {
> -            drop_ld_preload = 1;
> +           (void) envlist_unsetenv(envlist, "LD_PRELOAD");
>          } else if (!strcmp(r, "strace")) {
>              do_strace = 1;
>          } else
> @@ -2374,19 +2403,8 @@ int main(int argc, char **argv, char **envp)
>          do_strace = 1;
>      }
>  
> -    wrk = environ;
> -    while (*(wrk++))
> -        environ_count++;
> -
> -    target_environ = malloc((environ_count + 1) * sizeof(char *));
> -    if (!target_environ)
> -        abort();
> -    for (wrk = environ, dst = target_environ; *wrk; wrk++) {
> -        if (drop_ld_preload && !strncmp(*wrk, "LD_PRELOAD=", 11))
> -            continue;
> -        *(dst++) = strdup(*wrk);
> -    }
> -    *dst = NULL; /* NULL terminate target_environ */
> +    target_environ = envlist_to_environ(envlist, NULL);
> +    envlist_free(envlist);
>  
>      if (loader_exec(filename, argv+optind, target_environ, regs, info) != 0) 
> {
>          printf("Error loading %s\n", filename);
> -- 
> 1.5.6.5
> 
> 
> -- 
> "rm -rf" only sounds scary if you don't have backups
> 
> 
> 

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net




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