[xen stable-4.13] x86/dom0: improve PVH initrd and metadata placement

[patchbot@xxxxxxx]

commit a99de9de81c7f1c8af532a23b895806225eaf192
Author:     Roger Pau Monné <roger.pau@xxxxxxxxxx>
AuthorDate: Thu Apr 9 09:06:31 2020 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Apr 9 09:06:31 2020 +0200

    x86/dom0: improve PVH initrd and metadata placement
    
    Don't assume there's going to be enough space at the tail of the
    loaded kernel and instead try to find a suitable memory area where the
    initrd and metadata can be loaded.
    
    Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
    
    x86/dom0: Fix build with clang
    
    find_memory() isn't marked as __init, so if it isn't fully inlined, it ends 
up
    tripping:
    
      Error: size of dom0_build.o:.text is 0x0c1
    
    Fixes: 73b47eea21 "x86/dom0: improve PVH initrd and metadata placement"
    Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    master commit: 73b47eea21045556dc5334e4f17d0c05c23f3c16
    master date: 2020-03-05 10:43:15 +0100
    master commit: 40213cd8626bac712fa69c4978993e87b57a7d0c
    master date: 2020-03-05 18:11:51 +0000
---
 xen/arch/x86/hvm/dom0_build.c | 58 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/dom0_build.c b/xen/arch/x86/hvm/dom0_build.c
index 380412151b..9a46005494 100644
--- a/xen/arch/x86/hvm/dom0_build.c
+++ b/xen/arch/x86/hvm/dom0_build.c
@@ -491,6 +491,45 @@ static int __init pvh_populate_p2m(struct domain *d)
 #undef MB1_PAGES
 }
 
+static paddr_t __init find_memory(
+    const struct domain *d, const struct elf_binary *elf, size_t size)
+{
+    paddr_t kernel_start = (paddr_t)elf->dest_base & PAGE_MASK;
+    paddr_t kernel_end = ROUNDUP((paddr_t)elf->dest_base + elf->dest_size,
+                                 PAGE_SIZE);
+    unsigned int i;
+
+    /*
+     * The memory map is sorted and all RAM regions starts and sizes are
+     * aligned to page boundaries.
+     */
+    for ( i = 0; i < d->arch.nr_e820; i++ )
+    {
+        paddr_t start, end = d->arch.e820[i].addr + d->arch.e820[i].size;
+
+        /* Don't use memory below 1MB, as it could overwrite BDA/EBDA/IBFT. */
+        if ( end <= MB(1) || d->arch.e820[i].type != E820_RAM )
+            continue;
+
+        start = MAX(ROUNDUP(d->arch.e820[i].addr, PAGE_SIZE), MB(1));
+
+        ASSERT(IS_ALIGNED(start, PAGE_SIZE) && IS_ALIGNED(end, PAGE_SIZE));
+
+        if ( end <= kernel_start || start >= kernel_end )
+            ; /* No overlap, nothing to do. */
+        /* Deal with the kernel already being loaded in the region. */
+        else if ( kernel_start - start > end - kernel_end )
+            end = kernel_start;
+        else
+            start = kernel_end;
+
+        if ( end - start >= size )
+            return start;
+    }
+
+    return INVALID_PADDR;
+}
+
 static int __init pvh_load_kernel(struct domain *d, const module_t *image,
                                   unsigned long image_headroom,
                                   module_t *initrd, void *image_base,
@@ -547,7 +586,24 @@ static int __init pvh_load_kernel(struct domain *d, const 
module_t *image,
         return rc;
     }
 
-    last_addr = ROUNDUP(parms.virt_kend - parms.virt_base, PAGE_SIZE);
+    /*
+     * Find a RAM region big enough (and that doesn't overlap with the loaded
+     * kernel) in order to load the initrd and the metadata. Note it could be
+     * split into smaller allocations, done as a single region in order to
+     * simplify it.
+     */
+    last_addr = find_memory(d, &elf, sizeof(start_info) +
+                            (initrd ? ROUNDUP(initrd->mod_end, PAGE_SIZE) +
+                                      sizeof(mod)
+                                    : 0) +
+                            (cmdline ? ROUNDUP(strlen(cmdline) + 1,
+                                               elf_64bit(&elf) ? 8 : 4)
+                                     : 0));
+    if ( last_addr == INVALID_PADDR )
+    {
+        printk("Unable to find a memory region to load initrd and metadata\n");
+        return -ENOMEM;
+    }
 
     if ( initrd != NULL )
     {
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.13