Re: [Xen-devel] [PATCH 1 of 3 RESEND] libxl: Look for bootloader in libexec path

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2012-05-09 at 11:51 +0100, George Dunlap wrote:
> If the full path for a bootloader (such as pygrub or xenpvnetboot) is not
> given, look for it in the libexec path.

xend used to do something similar, see tools/python/xen/util/auxbin.py
where it searches in:
        SEARCHDIRS = [ BINDIR, SBINDIR, LIBEXEC, PRIVATE_BINDIR, XENFIRMWAREDIR 
]
where:
        SBINDIR="/usr/sbin"
        BINDIR="/usr/bin"
        LIBEXEC="/usr/lib/xen/bin"
        PRIVATE_BINDIR="/usr/lib/xen/bin"
        XENFIRMWAREDIR="/usr/lib/xen/boot"

I think since libxl uses execvp the first two are handled by path
expansion, the next two are what you are adding (so has priority over
$PATH in your patch, which I think is OK) and the last one is irrelevant
in this context (xend uses the same function for other contexts).

However in order to not differ on the first two execvp needs to be given
the opportunity to search the path, which means that you need to check
of your newly constructed bootloader exists, and if it doesn't then try
and continue with the relative path not the absolute one.

Also since this patch comes before the rename+symlink patch as it stands
this patch will temporarily break people who just have "pygrub" without
a path in their config.

Ian.

> Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxxxxx>
> 
> diff -r 8a86d841e6d4 -r e43157a86933 tools/libxl/libxl_bootloader.c
> --- a/tools/libxl/libxl_bootloader.c  Tue May 08 13:36:24 2012 +0200
> +++ b/tools/libxl/libxl_bootloader.c  Wed May 09 11:38:50 2012 +0100
> @@ -333,6 +333,7 @@ int libxl_run_bootloader(libxl_ctx *ctx,
>  
>      char tempdir_template[] = "/var/run/libxl/bl.XXXXXX";
>      char *tempdir;
> +    const char *bootloader = NULL;
>  
>      char *dom_console_xs_path;
>      char dom_console_slave_tty_path[PATH_MAX];
> @@ -397,6 +398,13 @@ int libxl_run_bootloader(libxl_ctx *ctx,
>          goto out_close;
>      }
>  
> +    bootloader = libxl__abs_path(gc, info->u.pv.bootloader,
> +                                 libxl__libexec_path());
> +    if ( bootloader == NULL ) {
> +        rc = ERROR_NOMEM;
> +        goto out_close;
> +    }
> +
>      /*
>       * We need to present the bootloader's tty as a pty slave that xenconsole
>       * can access.  Since the bootloader itself needs a pty slave,
> @@ -417,7 +425,7 @@ int libxl_run_bootloader(libxl_ctx *ctx,
>      dom_console_xs_path = libxl__sprintf(gc, "%s/console/tty", 
> libxl__xs_get_dompath(gc, domid));
>      libxl__xs_write(gc, XBT_NULL, dom_console_xs_path, "%s", 
> dom_console_slave_tty_path);
>  
> -    pid = fork_exec_bootloader(&bootloader_fd, info->u.pv.bootloader, args);
> +    pid = fork_exec_bootloader(&bootloader_fd, bootloader, args);
>      if (pid < 0) {
>          goto out_close;
>      }
> 
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> http://lists.xen.org/xen-devel



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