driver: Avoid dependency on additional kernel symbol exports

If CONFIG_KALLSYMS_ALL is enabled, we can get symbol addresses that the
upstream kernel does not export via kallsyms_lookup_name. We can use
this to avoid a number of kernel patches. Specifically, x86 can become
patch-free once all guest-side support is merged and ivshmem-net is
built as external module (or merged as well).

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

1 files changed, 42 insertions, 9 deletions

diff --git a/driver/main.c b/driver/main.c
index af4930f3..ee585848 100644
--- a/driver/main.c
+++ b/driver/main.c
@@ -22,6 +22,7 @@
 #include <linux/miscdevice.h>
 #include <linux/firmware.h>
 #include <linux/mm.h>
+#include <linux/kallsyms.h>
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(4,11,0)
 #include <linux/sched/signal.h>
 #endif
@@ -75,9 +76,7 @@ MODULE_FIRMWARE(JAILHOUSE_FW_NAME);
 #endif
 MODULE_VERSION(JAILHOUSE_VERSION);
 
-#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
 extern unsigned int __hyp_stub_vectors[];
-#endif
 
 struct console_state {
         unsigned int head;
@@ -96,6 +95,17 @@ static struct jailhouse_console* volatile console_page;
 static bool console_available;
 static struct resource *hypervisor_mem_res;
 
+static typeof(ioremap_page_range) *ioremap_page_range_sym;
+#ifdef CONFIG_X86
+static typeof(lapic_timer_frequency) *lapic_timer_frequency_sym;
+#endif
+#ifdef CONFIG_ARM
+static typeof(__boot_cpu_mode) *__boot_cpu_mode_sym;
+#endif
+#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
+static typeof(__hyp_stub_vectors) *__hyp_stub_vectors_sym;
+#endif
+
 /* last_console contains three members:
  *   - valid: indicates if content in the page member is present
  *   - id:    hint for the consumer if it already consumed the content
@@ -191,9 +201,9 @@ void *jailhouse_ioremap(phys_addr_t phys, unsigned long virt,
                 return NULL;
         vma->phys_addr = phys;
 
-        if (ioremap_page_range((unsigned long)vma->addr,
-                               (unsigned long)vma->addr + size, phys,
-                               PAGE_KERNEL_EXEC)) {
+        if (ioremap_page_range_sym((unsigned long)vma->addr,
+                                   (unsigned long)vma->addr + size, phys,
+                                   PAGE_KERNEL_EXEC)) {
                 vunmap(vma->addr);
                 return NULL;
         }
@@ -374,7 +384,9 @@ static int jailhouse_cmd_enable(struct jailhouse_system __user *arg)
                 goto error_unlock;
 
 #ifdef CONFIG_ARM
-        if (!is_hyp_mode_available()) {
+        /* open-coded is_hyp_mode_available to use __boot_cpu_mode_sym */
+        if ((*__boot_cpu_mode_sym & MODE_MASK) != HYP_MODE ||
+            (*__boot_cpu_mode_sym) & BOOT_CPU_MODE_MISMATCH) {
                 pr_err("jailhouse: HYP mode not available\n");
                 err = -ENODEV;
                 goto error_put_module;
@@ -444,7 +456,7 @@ static int jailhouse_cmd_enable(struct jailhouse_system __user *arg)
         header->max_cpus = max_cpus;
 
 #if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
-        header->arm_linux_hyp_vectors = virt_to_phys(__hyp_stub_vectors);
+        header->arm_linux_hyp_vectors = virt_to_phys(*__hyp_stub_vectors_sym);
 #if LINUX_VERSION_CODE < KERNEL_VERSION(4,12,0)
         header->arm_linux_hyp_abi = HYP_STUB_ABI_LEGACY;
 #else
@@ -511,7 +523,7 @@ static int jailhouse_cmd_enable(struct jailhouse_system __user *arg)
                 config->platform_info.x86.tsc_khz = tsc_khz;
         if (config->platform_info.x86.apic_khz == 0)
                 config->platform_info.x86.apic_khz =
-                        lapic_timer_frequency / (1000 / HZ);
+                        *lapic_timer_frequency_sym / (1000 / HZ);
 #endif
 
         err = jailhouse_cell_prepare_root(&config->root_cell);
@@ -649,7 +661,7 @@ static int jailhouse_cmd_disable(void)
          * This flag has been set when onlining a CPU under Jailhouse
          * supervision into SVC instead of HYP mode.
          */
-        __boot_cpu_mode &= ~BOOT_CPU_MODE_MISMATCH;
+        *__boot_cpu_mode_sym &= ~BOOT_CPU_MODE_MISMATCH;
 #endif
 
         atomic_set(&call_done, 0);
@@ -850,6 +862,27 @@ static int __init jailhouse_init(void)
 {
         int err;
 
+#ifdef CONFIG_KALLSYMS_ALL
+#define RESOLVE_EXTERNAL_SYMBOL(symbol)                         \
+        symbol##_sym = (void *)kallsyms_lookup_name(#symbol);   \
+        if (!symbol##_sym)                                      \
+                return -EINVAL
+#else
+#define RESOLVE_EXTERNAL_SYMBOL(symbol)                         \
+        symbol##_sym = &symbol
+#endif
+
+        RESOLVE_EXTERNAL_SYMBOL(ioremap_page_range);
+#ifdef CONFIG_X86
+        RESOLVE_EXTERNAL_SYMBOL(lapic_timer_frequency);
+#endif
+#ifdef CONFIG_ARM
+        RESOLVE_EXTERNAL_SYMBOL(__boot_cpu_mode);
+#endif
+#if defined(CONFIG_ARM) || defined(CONFIG_ARM64)
+        RESOLVE_EXTERNAL_SYMBOL(__hyp_stub_vectors);
+#endif
+
         jailhouse_dev = root_device_register("jailhouse");
         if (IS_ERR(jailhouse_dev))
                 return PTR_ERR(jailhouse_dev);