[Xen-devel] [PATCH 4.0-testing 01/10] libxc: Do not use dom0 physmem as parameter to lzma decoder

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

From: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>

It's not clear why a userspace lzma decode would want to use that
particular value, what bearing it has on anything or why it would
assume it could use 1/3 of the total RAM in the system (potentially
quite a large amount of RAM) as opposed to any other limit number.

Instead, hardcode 32Mby.

This reverts 22830:c80960244942, removes the xc_get_physmem/physmem
function entirely, and replaces the expression at the call site with a
fixed constant.

Signed-off-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Acked-by: Ian Campbell <Ian.Campbell@xxxxxxxxxxxxx>
Cc: Christoph Egger <Christoph.Egger@xxxxxxx>
Committed-by: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
---
 tools/libxc/xc_dom_bzimageloader.c |   23 +----------------------
 1 files changed, 1 insertions(+), 22 deletions(-)

diff --git a/tools/libxc/xc_dom_bzimageloader.c 
b/tools/libxc/xc_dom_bzimageloader.c
index 398dbff..aa5abc7 100644
--- a/tools/libxc/xc_dom_bzimageloader.c
+++ b/tools/libxc/xc_dom_bzimageloader.c
@@ -149,27 +149,6 @@ static int xc_try_bzip2_decode(
 
 #include <lzma.h>
 
-static uint64_t physmem(void)
-{
-    uint64_t ret = 0;
-    const long pagesize = sysconf(_SC_PAGESIZE);
-    const long pages = sysconf(_SC_PHYS_PAGES);
-
-    if ( (pagesize != -1) || (pages != -1) )
-    {
-        /*
-         * According to docs, pagesize * pages can overflow.
-         * Simple case is 32-bit box with 4 GiB or more RAM,
-         * which may report exactly 4 GiB of RAM, and "long"
-         * being 32-bit will overflow. Casting to uint64_t
-         * hopefully avoids overflows in the near future.
-         */
-        ret = (uint64_t)(pagesize) * (uint64_t)(pages);
-    }
-
-    return ret;
-}
-
 static int xc_try_lzma_decode(
     struct xc_dom_image *dom, void **blob, size_t *size)
 {
@@ -182,7 +161,7 @@ static int xc_try_lzma_decode(
     int outsize;
     const char *msg;
 
-    ret = lzma_alone_decoder(&stream, physmem() / 3);
+    ret = lzma_alone_decoder(&stream, 32*1024*1024);
     if ( ret != LZMA_OK )
     {
         xc_dom_printf("LZMA: Failed to init stream decoder\n");
-- 
1.7.2.5


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