[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH 03/10] tools/libxg: Fix uninitialised variable in meminit()

Hi Andrew,

On 12/02/2021 15:39, Andrew Cooper wrote:
Various version of gcc, when compiling with -Og, complain:

   xg_dom_arm.c: In function 'meminit':
   xg_dom_arm.c:420:19: error: 'p2m_size' may be used uninitialized in this 
function [-Werror=maybe-uninitialized]
     420 |     dom->p2m_size = p2m_size;
         |     ~~~~~~~~~~~~~~^~~~~~~~~~

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

This was reported nearly 3 years ago (see [1]) and it is pretty sad this was never merged :(.

CC: Ian Jackson <iwj@xxxxxxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>

Julien/Stefano: I can't work out how this variable is supposed to work, and
the fact that it isn't a straight accumulation across the RAM banks looks

It looks buggy, but the P2M is never used on Arm. In fact, you sent a patch a year ago to drop it (see [2]). It would be nice to revive it.

  tools/libs/guest/xg_dom_arm.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/libs/guest/xg_dom_arm.c b/tools/libs/guest/xg_dom_arm.c
index 94948d2b20..f1b8d06f75 100644
--- a/tools/libs/guest/xg_dom_arm.c
+++ b/tools/libs/guest/xg_dom_arm.c
@@ -373,7 +373,7 @@ static int meminit(struct xc_dom_image *dom)
      const uint64_t modsize = dtb_size + ramdisk_size;
      const uint64_t ram128mb = bankbase[0] + (128<<20);
- xen_pfn_t p2m_size;
+    xen_pfn_t p2m_size = 0;
      uint64_t bank0end;
assert(dom->rambase_pfn << XC_PAGE_SHIFT == bankbase[0]);

If your original series is too risky for 4.15, I would consider to remote p2m_size completely and always 0 dom->p2m_size.


[1] https://lore.kernel.org/xen-devel/20180314123203.30646-1-wei.liu2@xxxxxxxxxx/ [2] https://patchwork.kernel.org/project/xen-devel/patch/20191217201550.15864-3-andrew.cooper3@xxxxxxxxxx/

Julien Grall



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.