[PATCH for-4.20? 1/4] ARM32/traps: Fix do_trap_undefined_instruction()'s detection of kernel text

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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);

fails 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 any
livepatch which brings in an adjusted BUG_FRAME().

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

Commit c8d4b6304a5e ("xen/arm: add support for run_in_exception_handler()"),
made run_in_exception_handler() work, but didn't complete the TODO left in
commit 3e802c6ca1fb ("xen/arm: Correctly support WARN_ON").  Do so, to make
ARM consistent with other architectures.

Fixes: 3e802c6ca1fb ("xen/arm: Correctly support WARN_ON")
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
CC: Michal Orzel <michal.orzel@xxxxxxx>
CC: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>

Sample run going wrong:
  https://gitlab.com/xen-project/people/andyhhp/xen/-/jobs/9078570105

Sample run with dump_execution_state() working:
  https://gitlab.com/xen-project/people/andyhhp/xen/-/jobs/9079185111
---
 xen/arch/arm/arm32/traps.c           | 3 +--
 xen/arch/arm/include/asm/processor.h | 3 +--
 2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/arm32/traps.c b/xen/arch/arm/arm32/traps.c
index a2fc1c22cbc9..b88d41811b49 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 */
diff --git a/xen/arch/arm/include/asm/processor.h 
b/xen/arch/arm/include/asm/processor.h
index 60b587db697f..d80d44aeaa8f 100644
--- a/xen/arch/arm/include/asm/processor.h
+++ b/xen/arch/arm/include/asm/processor.h
@@ -577,8 +577,7 @@ void panic_PAR(uint64_t par);
 void show_registers(const struct cpu_user_regs *regs);
 void show_stack(const struct cpu_user_regs *regs);
 
-//#define dump_execution_state() run_in_exception_handler(show_execution_state)
-#define dump_execution_state() WARN()
+#define dump_execution_state() run_in_exception_handler(show_execution_state)
 
 #define cpu_relax() barrier() /* Could yield? */
 
-- 
2.39.5