[Xen-devel] [PATCH] libxc: Have xc_translate_foreign_address() set errno properly

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

Currently it's possible for xc_translate_foreign_address() to fail
and errno still be set to success. This patch fixes the issue.
Based on the first half of Don Slutz' patch:
http://lists.xen.org/archives/html/xen-devel/2014-03/msg03720.html

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
---
 tools/libxc/xc_pagetab.c | 36 +++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/tools/libxc/xc_pagetab.c b/tools/libxc/xc_pagetab.c
index ec97890..f7dc30b 100644
--- a/tools/libxc/xc_pagetab.c
+++ b/tools/libxc/xc_pagetab.c
@@ -34,9 +34,14 @@ unsigned long xc_translate_foreign_address(xc_interface 
*xch, uint32_t dom,
     int size, level, pt_levels = 2;
     void *map;
 
-    if (xc_domain_getinfo(xch, dom, 1, &dominfo) != 1 
+    if (xc_domain_getinfo(xch, dom, 1, &dominfo) != 1
         || dominfo.domid != dom)
+    {
+        if (errno == 0)
+            errno = EINVAL;
+
         return 0;
+    }
 
     /* What kind of paging are we dealing with? */
     if (dominfo.hvm) {
@@ -44,7 +49,12 @@ unsigned long xc_translate_foreign_address(xc_interface 
*xch, uint32_t dom,
         if (xc_domain_hvm_getcontext_partial(xch, dom,
                                              HVM_SAVE_CODE(CPU), vcpu,
                                              &ctx, sizeof ctx) != 0)
+        {
+            if (errno == 0)
+                errno = EINVAL;
+
             return 0;
+        }
         if (!(ctx.cr0 & CR0_PG))
             return virt >> PAGE_SHIFT;
         pt_levels = (ctx.msr_efer&EFER_LMA) ? 4 : (ctx.cr4&CR4_PAE) ? 3 : 2;
@@ -53,9 +63,19 @@ unsigned long xc_translate_foreign_address(xc_interface 
*xch, uint32_t dom,
         unsigned int gwidth;
         vcpu_guest_context_any_t ctx;
         if (xc_vcpu_getcontext(xch, dom, vcpu, &ctx) != 0)
+        {
+            if (errno == 0)
+                errno = EINVAL;
+
             return 0;
+        }
         if (xc_domain_get_guest_width(xch, dom, &gwidth) != 0)
+        {
+            if (errno == 0)
+                errno = EINVAL;
+
             return 0;
+        }
         if (gwidth == 8) {
             pt_levels = 4;
             paddr = (uint64_t)xen_cr3_to_pfn_x86_64(ctx.x64.ctrlreg[3])
@@ -84,12 +104,22 @@ unsigned long xc_translate_foreign_address(xc_interface 
*xch, uint32_t dom,
         paddr += ((virt & mask) >> (xc_ffs64(mask) - 1)) * size;
         map = xc_map_foreign_range(xch, dom, PAGE_SIZE, PROT_READ, 
                                    paddr >>PAGE_SHIFT);
-        if (!map) 
+        if (!map)
+        {
+            if (errno == 0)
+                errno = EINVAL;
+
             return 0;
+        }
         memcpy(&pte, map + (paddr & (PAGE_SIZE - 1)), size);
         munmap(map, PAGE_SIZE);
-        if (!(pte & 1)) 
+        if (!(pte & 1))
+        {
+            if (errno == 0)
+                errno = EADDRNOTAVAIL;
+
             return 0;
+        }
         paddr = pte & 0x000ffffffffff000ull;
         if (level == 2 && (pte & PTE_PSE)) {
             mask = ((mask ^ ~-mask) >> 1); /* All bits below first set bit */
-- 
1.9.1


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