From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Fri, 7 Feb 2025 23:15:01 +0000 (+0000)
Subject: ARM32/traps: Fix do_trap_undefined_instruction()'s detection of kernel text
X-Git-Tag: 4.20.0-rc5~6
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=414dde38b0cf8a38230c8c3f9e8564da9762e743;p=xen.git

ARM32/traps: Fix do_trap_undefined_instruction()'s detection of kernel text

While fixing some common/arch boundaries for UBSAN support on other
architectures, the following debugging patch:

  diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
  index c1f2d1b89d43..58d1d048d339 100644
  --- a/xen/arch/arm/setup.c
  +++ b/xen/arch/arm/setup.c
  @@ -504,6 +504,8 @@ void asmlinkage __init start_xen(unsigned long fdt_paddr)

       system_state = SYS_STATE_active;

  +    dump_execution_state();
  +
       for_each_domain( d )
           domain_unpause_by_systemcontroller(d);

failed with:

  (XEN) *** Serial input to DOM0 (type 'CTRL-a' three times to switch input)
  (XEN) CPU0: Unexpected Trap: Undefined Instruction
  (XEN) ----[ Xen-4.20-rc  arm32  debug=n  Not tainted ]----
  (XEN) CPU:    0
  <snip>
  (XEN)
  (XEN) ****************************************
  (XEN) Panic on CPU 0:
  (XEN) CPU0: Unexpected Trap: Undefined Instruction
  (XEN) ****************************************

This is because the condition for init text is wrong.  While there's nothing
interesting from that point onwards in start_xen(), it's also wrong for
livepatches too.

Use is_active_kernel_text() which is the correct test for this purpose, and is
aware of init and livepatch regions as well as their lifetimes.

Fixes: 3e802c6ca1fb ("xen/arm: Correctly support WARN_ON")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Julien Grall <jgrall@amazon.com>
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@gmail.com>
---

diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
index a2fc1c22cb..b88d41811b 100644
--- a/xen/arch/arm/arm32/traps.c
+++ b/xen/arch/arm/arm32/traps.c
@@ -36,8 +36,7 @@ void do_trap_undefined_instruction(struct cpu_user_regs *regs)
     uint32_t pc = regs->pc;
     uint32_t instr;
 
-    if ( !is_kernel_text(pc) &&
-         (system_state >= SYS_STATE_active || !is_kernel_inittext(pc)) )
+    if ( !is_active_kernel_text(pc) )
         goto die;
 
     /* PC should be always a multiple of 4, as Xen is using ARM instruction set */