[Xen-devel] [PATCH v20 01/13] common/symbols: Export hypervisor symbols to privileged guest

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Export Xen's symbols as {<address><type><name>} triplet via new XENPF_get_symbol
hypercall

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Acked-by: Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Reviewed-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
Tested-by: Dietmar Hahn <dietmar.hahn@xxxxxxxxxxxxxx>
---
 xen/arch/x86/platform_hypercall.c   | 28 +++++++++++++++++++
 xen/common/symbols.c                | 54 +++++++++++++++++++++++++++++++++++++
 xen/include/public/platform.h       | 19 +++++++++++++
 xen/include/xen/symbols.h           |  3 +++
 xen/include/xlat.lst                |  1 +
 xen/xsm/flask/hooks.c               |  4 +++
 xen/xsm/flask/policy/access_vectors |  2 ++
 7 files changed, 111 insertions(+)

diff --git a/xen/arch/x86/platform_hypercall.c 
b/xen/arch/x86/platform_hypercall.c
index 334d474..7626261 100644
--- a/xen/arch/x86/platform_hypercall.c
+++ b/xen/arch/x86/platform_hypercall.c
@@ -23,6 +23,7 @@
 #include <xen/cpu.h>
 #include <xen/pmstat.h>
 #include <xen/irq.h>
+#include <xen/symbols.h>
 #include <asm/current.h>
 #include <public/platform.h>
 #include <acpi/cpufreq/processor_perf.h>
@@ -798,6 +799,33 @@ ret_t 
do_platform_op(XEN_GUEST_HANDLE_PARAM(xen_platform_op_t) u_xenpf_op)
     }
     break;
 
+    case XENPF_get_symbol:
+    {
+        static char name[KSYM_NAME_LEN + 1]; /* protected by xenpf_lock */
+        XEN_GUEST_HANDLE(char) nameh;
+        uint32_t namelen, copylen;
+
+        guest_from_compat_handle(nameh, op->u.symdata.name);
+
+        ret = xensyms_read(&op->u.symdata.symnum, &op->u.symdata.type,
+                           &op->u.symdata.address, name);
+
+        namelen = strlen(name) + 1;
+
+        if ( namelen > op->u.symdata.namelen )
+            copylen = op->u.symdata.namelen;
+        else
+            copylen = namelen;
+
+        op->u.symdata.namelen = namelen;
+
+        if ( !ret && copy_to_guest(nameh, name, copylen) )
+            ret = -EFAULT;
+        if ( !ret && __copy_field_to_guest(u_xenpf_op, op, u.symdata) )
+            ret = -EFAULT;
+    }
+    break;
+
     default:
         ret = -ENOSYS;
         break;
diff --git a/xen/common/symbols.c b/xen/common/symbols.c
index fc7c9e7..a2276da 100644
--- a/xen/common/symbols.c
+++ b/xen/common/symbols.c
@@ -17,6 +17,8 @@
 #include <xen/lib.h>
 #include <xen/string.h>
 #include <xen/spinlock.h>
+#include <public/platform.h>
+#include <xen/guest_access.h>
 
 #ifdef SYMBOLS_ORIGIN
 extern const unsigned int symbols_offsets[];
@@ -148,3 +150,55 @@ const char *symbols_lookup(unsigned long addr,
     *offset = addr - symbols_address(low);
     return namebuf;
 }
+
+/*
+ * Get symbol type information. This is encoded as a single char at the
+ * beginning of the symbol name.
+ */
+static char symbols_get_symbol_type(unsigned int off)
+{
+    /*
+     * Get just the first code, look it up in the token table,
+     * and return the first char from this token.
+     */
+    return symbols_token_table[symbols_token_index[symbols_names[off + 1]]];
+}
+
+int xensyms_read(uint32_t *symnum, char *type,
+                 uint64_t *address, char *name)
+{
+    /*
+     * Symbols are most likely accessed sequentially so we remember position
+     * from previous read. This can help us avoid the extra call to
+     * get_symbol_offset().
+     */
+    static uint64_t next_symbol, next_offset;
+    static DEFINE_SPINLOCK(symbols_mutex);
+
+    if ( *symnum > symbols_num_syms )
+        return -ERANGE;
+    if ( *symnum == symbols_num_syms )
+    {
+        /* No more symbols */
+        name[0] = '\0';
+        return 0;
+    }
+
+    spin_lock(&symbols_mutex);
+
+    if ( *symnum == 0 )
+        next_offset = next_symbol = 0;
+    if ( next_symbol != *symnum )
+        /* Non-sequential access */
+        next_offset = get_symbol_offset(*symnum);
+
+    *type = symbols_get_symbol_type(next_offset);
+    next_offset = symbols_expand_symbol(next_offset, name);
+    *address = symbols_offsets[*symnum] + SYMBOLS_ORIGIN;
+
+    next_symbol = ++*symnum;
+
+    spin_unlock(&symbols_mutex);
+
+    return 0;
+}
diff --git a/xen/include/public/platform.h b/xen/include/public/platform.h
index 82ec84e..1e6a6ce 100644
--- a/xen/include/public/platform.h
+++ b/xen/include/public/platform.h
@@ -590,6 +590,24 @@ struct xenpf_resource_op {
 typedef struct xenpf_resource_op xenpf_resource_op_t;
 DEFINE_XEN_GUEST_HANDLE(xenpf_resource_op_t);
 
+#define XENPF_get_symbol   63
+struct xenpf_symdata {
+    /* IN/OUT variables */
+    uint32_t namelen; /* IN:  size of name buffer                       */
+                      /* OUT: strlen(name) of hypervisor symbol (may be */
+                      /*      larger than what's been copied to guest)  */
+    uint32_t symnum;  /* IN:  Symbol to read                            */
+                      /* OUT: Next available symbol. If same as IN then */
+                      /*      we reached the end                        */
+
+    /* OUT variables */
+    XEN_GUEST_HANDLE(char) name;
+    uint64_t address;
+    char type;
+};
+typedef struct xenpf_symdata xenpf_symdata_t;
+DEFINE_XEN_GUEST_HANDLE(xenpf_symdata_t);
+
 /*
  * ` enum neg_errnoval
  * ` HYPERVISOR_platform_op(const struct xen_platform_op*);
@@ -619,6 +637,7 @@ struct xen_platform_op {
         struct xenpf_mem_hotadd        mem_add;
         struct xenpf_core_parking      core_parking;
         struct xenpf_resource_op       resource_op;
+        struct xenpf_symdata           symdata;
         uint8_t                        pad[128];
     } u;
 };
diff --git a/xen/include/xen/symbols.h b/xen/include/xen/symbols.h
index 87cd77d..1fa0537 100644
--- a/xen/include/xen/symbols.h
+++ b/xen/include/xen/symbols.h
@@ -11,4 +11,7 @@ const char *symbols_lookup(unsigned long addr,
                            unsigned long *offset,
                            char *namebuf);
 
+int xensyms_read(uint32_t *symnum, char *type,
+                 uint64_t *address, char *name);
+
 #endif /*_XEN_SYMBOLS_H*/
diff --git a/xen/include/xlat.lst b/xen/include/xlat.lst
index 9c9fd9a..906e6fc 100644
--- a/xen/include/xlat.lst
+++ b/xen/include/xlat.lst
@@ -89,6 +89,7 @@
 ?      processor_px                    platform.h
 !      psd_package                     platform.h
 ?      xenpf_enter_acpi_sleep          platform.h
+!      xenpf_symdata                   platform.h
 ?      xenpf_pcpuinfo                  platform.h
 ?      xenpf_pcpu_version              platform.h
 ?      xenpf_resource_entry            platform.h
diff --git a/xen/xsm/flask/hooks.c b/xen/xsm/flask/hooks.c
index 34e5ab4..77026f1 100644
--- a/xen/xsm/flask/hooks.c
+++ b/xen/xsm/flask/hooks.c
@@ -1408,6 +1408,10 @@ static int flask_platform_op(uint32_t op)
         return avc_current_has_perm(SECINITSID_XEN, SECCLASS_XEN2,
                                     XEN2__RESOURCE_OP, NULL);
 
+    case XENPF_get_symbol:
+        return avc_has_perm(domain_sid(current->domain), SECINITSID_XEN,
+                            SECCLASS_XEN2, XEN2__GET_SYMBOL, NULL);
+
     default:
         printk("flask_platform_op: Unknown op %d\n", op);
         return -EPERM;
diff --git a/xen/xsm/flask/policy/access_vectors 
b/xen/xsm/flask/policy/access_vectors
index f89825c..649b3d4 100644
--- a/xen/xsm/flask/policy/access_vectors
+++ b/xen/xsm/flask/policy/access_vectors
@@ -84,6 +84,8 @@ class xen2
     resource_op
 # XEN_SYSCTL_psr_cmt_op
     psr_cmt_op
+# XENPF_get_symbol
+    get_symbol
 }
 
 # Classes domain and domain2 consist of operations that a domain performs on
-- 
1.8.1.4


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