On Fri, Jun 19, 2015 at 12:13:36PM +0200, Gerd Hoffmann wrote:
> This is what it takes to have a sorted fw_cfg file directory.
> Entries are inserted at the correct place instead of being
> appended to the end in case sorting is enabled.
On Mon, Jun 08, 2015 at 05:53:48PM +0200, Michael S. Tsirkin wrote:
> Unfortunately we have a bunch of code adding fw cfg entries
> after machine ready.
I'm not really clear about the relationship between "after machine
ready" and "after guest vcpu begins executing instructions", but as
long as we never insert new fw_cfg files after the *latter*, this
should work fine.
Otherwise, there's a chance that guest code might grab a selector
value which would become stale if the fw_cfg structures are re-sorted
due to a new blob being inserted.
Thanks,
--Gabriel
> Compatibility fluff (enable sorting for new machine types only)
> isn't there yet.
>
> Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
> ---
> hw/nvram/fw_cfg.c | 30 ++++++++++++++++++++++++------
> 1 file changed, 24 insertions(+), 6 deletions(-)
>
> diff --git a/hw/nvram/fw_cfg.c b/hw/nvram/fw_cfg.c
> index 0f35931..83205e0 100644
> --- a/hw/nvram/fw_cfg.c
> +++ b/hw/nvram/fw_cfg.c
> @@ -639,7 +639,7 @@ void fw_cfg_add_file_callback(FWCfgState *s, const char
> *filename,
> FWCfgReadCallback callback, void
> *callback_opaque,
> void *data, size_t len)
> {
> - int i, index;
> + int i, index, count;
> size_t dsize;
>
> if (!s->files) {
> @@ -648,13 +648,31 @@ void fw_cfg_add_file_callback(FWCfgState *s, const
> char *filename,
> fw_cfg_add_bytes(s, FW_CFG_FILE_DIR, s->files, dsize);
> }
>
> - index = be32_to_cpu(s->files->count);
> - assert(index < FW_CFG_FILE_SLOTS);
> + count = be32_to_cpu(s->files->count);
> + assert(count < FW_CFG_FILE_SLOTS);
> +
> + index = count;
> + if (1 /* sort entries */) {
> + while (index > 0 && strcmp(filename, s->files->f[index-1].name) < 0)
> {
> + s->files->f[index] =
> + s->files->f[index - 1];
> + s->files->f[index].select =
> + cpu_to_be16(FW_CFG_FILE_FIRST + index);
> + s->entries[0][FW_CFG_FILE_FIRST + index] =
> + s->entries[0][FW_CFG_FILE_FIRST + index - 1];
> + index--;
> + }
> + memset(&s->files->f[index],
> + 0, sizeof(FWCfgFile));
> + memset(&s->entries[0][FW_CFG_FILE_FIRST + index],
> + 0, sizeof(FWCfgEntry));
> + }
>
> pstrcpy(s->files->f[index].name, sizeof(s->files->f[index].name),
> filename);
> - for (i = 0; i < index; i++) {
> - if (strcmp(s->files->f[index].name, s->files->f[i].name) == 0) {
> + for (i = 0; i <= count; i++) {
> + if (i != index &&
> + strcmp(s->files->f[index].name, s->files->f[i].name) == 0) {
> error_report("duplicate fw_cfg file name: %s",
> s->files->f[index].name);
> exit(1);
> @@ -668,7 +686,7 @@ void fw_cfg_add_file_callback(FWCfgState *s, const char
> *filename,
> s->files->f[index].select = cpu_to_be16(FW_CFG_FILE_FIRST + index);
> trace_fw_cfg_add_file(s, index, s->files->f[index].name, len);
>
> - s->files->count = cpu_to_be32(index+1);
> + s->files->count = cpu_to_be32(count+1);
> }
>
> void fw_cfg_add_file(FWCfgState *s, const char *filename,
> --
> 1.8.3.1
>
