Commit: 23295de1317433210cb0303ef304e68763607c78 - binutils_gdb (git)

Commit MetaInfo

• Révision: 23295de1317433210cb0303ef304e68763607c78 (tree)
• l'heure: 2022-10-26 21:00:50
• Auteur: Luis Machado <luis.machado@arm....>
• Commiter: Luis Machado

Message de Log

gdb/arm: Fix M-profile EXC_RETURN

Arm v8-M Architecture Reference Manual,
D1.2.95 EXC_RETURN, Exception Return Payload
describes ES bit:

"ES, bit [0]

Exception Secure. The security domain the exception was taken to.
The possible values of this bit are:

0 Non-secure.
1 Secure"

arm-tdep.c:3443, arm_m_exception_cache () function tests this bit:

exception_domain_is_secure = (bit (lr, 0) == 0);

The test is negated!

Later on line 3553, the condition evaluates if an additional state
context is stacked:

/* With the Security extension, the hardware saves R4..R11 too. */
if (tdep->have_sec_ext && secure_stack_used

&& (!default_callee_register_stacking || exception_domain_is_secure))

RM, B3.19 Exception entry, context stacking
reads:
RPLHM "In a PE with the Security Extension, on taking an exception,
the PE hardware:

...

1. If exception entry requires a transition from Secure state to
   Non-secure state, the PE hardware extends the stack frame and also
   saves additional state context."
   

So we should test for !exception_domain_is_secure instead of non-negated
value!
These two bugs compensate each other so unstacking works correctly.

But another test of exception_domain_is_secure (negated due to the
first bug) prevents arm_unwind_secure_frames to work as expected:

/* Unwinding from non-secure to secure can trip security

1. 1. 1. In order to avoid the debugger being
         intrusive, rely on the user to configure the requested
         
      2. */
         

if (secure_stack_used && !exception_domain_is_secure

&& !arm_unwind_secure_frames)

Test with GNU gdb (GDB) 13.0.50.20221016-git.
Stopped in a non-secure handler:

(gdb) set arm unwind-secure-frames 0
(gdb) bt
#0 HAL_SYSTICK_Callback () at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/NonSecure/Src/nsmain.c:490
#1 0x0804081c in SysTick_Handler ()

at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/NonSecure/Src/nsstm32l5xx_it.c:134

#2 <signal handler called>
#3 HAL_GPIO_ReadPin (GPIOx=0x52020800, GPIO_Pin=8192)

at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/Drivers/STM32L5xx_HAL_Driver/Src/stm32l5xx_hal_gpio.c:386

#4 0x0c000338 in SECURE_Mode () at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/Secure/Src/main.c:86
#5 0x080403f2 in main () at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/NonSecure/Src/nsmain.c:278
Backtrace stopped: previous frame inner to this frame (corrupt stack?)

The frames #3 and #4 are secure. backtrace should stop before #3.

Stopped in a secure handler:

(gdb) bt
#0 HAL_SYSTICK_Callback () at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/Secure/Src/main.c:425
#1 0x0c000b6a in SysTick_Handler ()

at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/Secure/Src/stm32l5xx_it.c:234

warning: Non-secure to secure stack unwinding disabled.
#2 <signal handler called>

The exception from secure to secure erroneously stops unwinding. It should
continue as far as the security unlimited backtrace:

(gdb) set arm unwind-secure-frames 1
(gdb) si <-- used to rebuild frame cache after change of unwind-secure-frames
0x0c0008e6 425 if (SecureTimingDelay != 0U)
(gdb) bt
#0 0x0c0008e6 in HAL_SYSTICK_Callback () at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/Secure/Src/main.c:425
#1 0x0c000b6a in SysTick_Handler ()

at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/Secure/Src/stm32l5xx_it.c:234

#2 <signal handler called>
#3 0x0c000328 in SECURE_Mode () at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/Secure/Src/main.c:88
#4 0x080403f2 in main () at C:/dvl/stm32l5trustzone/GPIO_IOToggle_TrustZone/NonSecure/Src/nsmain.c:278

Backtrace stopped: previous frame inner to this frame (corrupt stack?)

Set exception_domain_is_secure to the value expected by its name.
Fix exception_domain_is_secure usage in the additional state context
stacking condition.

Signed-off-by: Tomas Vanek <[e-mail]>

Change Summary

• modified: gdb/arm-tdep.c

Modification

--- a/gdb/arm-tdep.c
+++ b/gdb/arm-tdep.c
@@ -3489,7 +3489,7 @@ arm_m_exception_cache (frame_info_ptr this_frame)
 	{
 	  secure_stack_used = (bit (lr, 6) != 0);
 	  default_callee_register_stacking = (bit (lr, 5) != 0);
-	  exception_domain_is_secure = (bit (lr, 0) == 0);
+	  exception_domain_is_secure = (bit (lr, 0) != 0);
 
 	  /* Unwinding from non-secure to secure can trip security
 	     measures.  In order to avoid the debugger being
@@ -3599,7 +3599,7 @@ arm_m_exception_cache (frame_info_ptr this_frame)
 
       /* With the Security extension, the hardware saves R4..R11 too.  */
       if (tdep->have_sec_ext && secure_stack_used
-	  && (!default_callee_register_stacking || exception_domain_is_secure))
+	  && (!default_callee_register_stacking || !exception_domain_is_secure))
 	{
 	  /* Read R4..R11 from the integer callee registers.  */
 	  cache->saved_regs[4].set_addr (unwound_sp + 0x08);