arch,entry,usermode: fix user pagetable mappings alignment

The exception handlers as well as interrupt handlers need to be properly mapped into user pagetables. Add global symbols to find their addresses and align the beginning on a page boundary. Similar entry_usermode() and syscall_handler_entry() need to be aligned and ideally share the same page. The syscall_exit() and similar routines do not need user pagetable mappings. Add also an explicit mapping for user_cr3 variable. Signed-off-by: Pawel Wieczorkiewicz <[email protected]>
KernelTestFramework · Aug 28, 2023 · f597ad1 · f597ad1
1 parent 9cff8c9
commit f597ad1
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Showing 3 changed files with 25 additions and 4 deletions.
diff --git a/arch/x86/entry.S b/arch/x86/entry.S
@@ -107,6 +107,8 @@ ENTRY(handle_exception)
     IRET
 END_FUNC(handle_exception)
 
+.align PAGE_SIZE
+GLOBAL(exception_handlers)
 exception_handler DE  X86_EX_DE  0
 exception_handler DB  X86_EX_DB  0
 exception_handler NMI X86_EX_NMI 0
@@ -129,14 +131,18 @@ exception_handler MC  X86_EX_MC  0
 exception_handler XM  X86_EX_XM  0
 exception_handler VE  X86_EX_VE  0
 exception_handler SE  X86_EX_SE  1
+GLOBAL(end_exception_handlers)
 
+GLOBAL(interrupt_handlers)
 interrupt_handler timer timer_interrupt_handler
 interrupt_handler uart uart_interrupt_handler
 interrupt_handler keyboard keyboard_interrupt_handler
 #ifdef KTF_ACPICA
 interrupt_handler acpi acpi_interrupt_handler
 #endif
+GLOBAL(end_interrupt_handlers)
 
+.align PAGE_SIZE
 ENTRY(syscall_exit)
     POPF
 
@@ -157,6 +163,8 @@ ENTRY(terminate_user_task)
     ret
 END_FUNC(terminate_user_task)
 
+.align PAGE_SIZE
+GLOBAL(usermode_helpers)
 ENTRY(enter_usermode)
     /* FIXME: Add 32-bit support */
 
@@ -184,7 +192,6 @@ ENTRY(enter_usermode)
     IRET
 END_FUNC(enter_usermode)
 
-.align PAGE_SIZE
 ENTRY(syscall_handler_entry)
     SAVE_CALLEE_SAVED_REGS
     syscall_from_usermode
@@ -206,6 +213,7 @@ ENTRY(syscall_handler_entry)
     RESTORE_CALLEE_SAVED_REGS
     SYSRET
 END_FUNC(syscall_handler_entry)
+GLOBAL(end_usermode_helpers)
 
 SECTION(.text.user, "ax", 16)
 ENTRY(usermode_stub)

diff --git a/arch/x86/pagetables.c b/arch/x86/pagetables.c
@@ -30,7 +30,7 @@
 #include <spinlock.h>
 #include <string.h>
 
-cr3_t cr3;
+cr3_t __aligned(PAGE_SIZE) cr3;
 cr3_t user_cr3;
 
 static inline const char *dump_pte_flags(char *buf, size_t size, pte_t pte) {

diff --git a/common/usermode.c b/common/usermode.c
@@ -28,6 +28,10 @@
 #include <processor.h>
 #include <usermode.h>
 
+extern char exception_handlers[], end_exception_handlers[];
+extern char interrupt_handlers[], end_interrupt_handlers[];
+extern char usermode_helpers[], end_usermode_helpers[];
+
 long syscall_handler(long syscall_nr, long arg1, long arg2, long arg3, long arg4,
                      long arg5) {
     switch (syscall_nr) {
@@ -89,8 +93,17 @@ static void init_syscall(void) {
 
 void init_usermode(percpu_t *percpu) {
     vmap_user_4k(&cr3, virt_to_mfn(&cr3), L1_PROT);
-    vmap_user_4k(&enter_usermode, virt_to_mfn(&enter_usermode), L1_PROT);
-    vmap_user_4k(&syscall_handler_entry, virt_to_mfn(&syscall_handler_entry), L1_PROT);
+    vmap_user_4k(&user_cr3, virt_to_mfn(&user_cr3), L1_PROT);
+
+    BUG_ON(end_exception_handlers - exception_handlers > (long) PAGE_SIZE);
+    vmap_user_4k(exception_handlers, virt_to_mfn(exception_handlers), L1_PROT);
+
+    BUG_ON(end_interrupt_handlers - interrupt_handlers > (long) PAGE_SIZE);
+    vmap_user_4k(interrupt_handlers, virt_to_mfn(interrupt_handlers), L1_PROT);
+
+    BUG_ON(end_usermode_helpers - usermode_helpers > (long) PAGE_SIZE);
+    vmap_user_4k(usermode_helpers, virt_to_mfn(usermode_helpers), L1_PROT);
+
     init_syscall();
 }