x86/traps: Cleanup do_general_protection()

Hoist the user_mode() case up because it is less code and can be dealt
with up-front like the other special cases UMIP and vm86.

This saves an indentation level for the kernel-mode #GP case and allows
to "unfold" the code more so that it is more readable.

No functional changes.

Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Jann Horn <jannh@google.com>
Cc: x86@kernel.org

diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 2afd7d8..ca395ad 100644 (file)
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -567,7 +567,10 @@ static enum kernel_gp_hint get_kernel_gp_address(struct pt_regs *regs,
 dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code)
 {
        char desc[sizeof(GPFSTR) + 50 + 2*sizeof(unsigned long) + 1] = GPFSTR;
+       enum kernel_gp_hint hint = GP_NO_HINT;
        struct task_struct *tsk;
+       unsigned long gp_addr;
+       int ret;
 
        RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
        cond_local_irq_enable(regs);
@@ -584,58 +587,56 @@ dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code)
        }
 
        tsk = current;
-       if (!user_mode(regs)) {
-               enum kernel_gp_hint hint = GP_NO_HINT;
-               unsigned long gp_addr;
-
-               if (fixup_exception(regs, X86_TRAP_GP, error_code, 0))
-                       return;
 
+       if (user_mode(regs)) {
                tsk->thread.error_code = error_code;
                tsk->thread.trap_nr = X86_TRAP_GP;
 
-               /*
-                * To be potentially processing a kprobe fault and to
-                * trust the result from kprobe_running(), we have to
-                * be non-preemptible.
-                */
-               if (!preemptible() && kprobe_running() &&
-                   kprobe_fault_handler(regs, X86_TRAP_GP))
-                       return;
+               show_signal(tsk, SIGSEGV, "", desc, regs, error_code);
+               force_sig(SIGSEGV);
 
-               if (notify_die(DIE_GPF, desc, regs, error_code,
-                              X86_TRAP_GP, SIGSEGV) == NOTIFY_STOP)
-                       return;
+               return;
+       }
 
-               if (error_code)
-                       snprintf(desc, sizeof(desc), "segment-related " GPFSTR);
-               else
-                       hint = get_kernel_gp_address(regs, &gp_addr);
+       if (fixup_exception(regs, X86_TRAP_GP, error_code, 0))
+               return;
 
-               if (hint != GP_NO_HINT)
-                       snprintf(desc, sizeof(desc), GPFSTR ", %s 0x%lx",
-                                (hint == GP_NON_CANONICAL) ?
-                                "probably for non-canonical address" :
-                                "maybe for address",
-                                gp_addr);
+       tsk->thread.error_code = error_code;
+       tsk->thread.trap_nr = X86_TRAP_GP;
 
-               /*
-                * KASAN is interested only in the non-canonical case, clear it
-                * otherwise.
-                */
-               if (hint != GP_NON_CANONICAL)
-                       gp_addr = 0;
+       /*
+        * To be potentially processing a kprobe fault and to trust the result
+        * from kprobe_running(), we have to be non-preemptible.
+        */
+       if (!preemptible() &&
+           kprobe_running() &&
+           kprobe_fault_handler(regs, X86_TRAP_GP))
+               return;
 
-               die_addr(desc, regs, error_code, gp_addr);
+       ret = notify_die(DIE_GPF, desc, regs, error_code, X86_TRAP_GP, SIGSEGV);
+       if (ret == NOTIFY_STOP)
                return;
-       }
 
-       tsk->thread.error_code = error_code;
-       tsk->thread.trap_nr = X86_TRAP_GP;
+       if (error_code)
+               snprintf(desc, sizeof(desc), "segment-related " GPFSTR);
+       else
+               hint = get_kernel_gp_address(regs, &gp_addr);
+
+       if (hint != GP_NO_HINT)
+               snprintf(desc, sizeof(desc), GPFSTR ", %s 0x%lx",
+                        (hint == GP_NON_CANONICAL) ? "probably for non-canonical address"
+                                                   : "maybe for address",
+                        gp_addr);
+
+       /*
+        * KASAN is interested only in the non-canonical case, clear it
+        * otherwise.
+        */
+       if (hint != GP_NON_CANONICAL)
+               gp_addr = 0;
 
-       show_signal(tsk, SIGSEGV, "", desc, regs, error_code);
+       die_addr(desc, regs, error_code, gp_addr);
 
-       force_sig(SIGSEGV);
 }
 NOKPROBE_SYMBOL(do_general_protection);