microblaze: Add KGDB support
Kgdb uses brki r16, 0x18 instruction to call
low level _debug_exception function which save
current state to pt_regs and call microblaze_kgdb_break
function. _debug_exception should be called only from
the kernel space. User space calling is not supported
because user application debugging uses different handling.
pt_regs_to_gdb_regs loads additional special registers
which can't be changed
* Enable KGDB in Kconfig
* Remove ancient not-tested KGDB support
* Remove ancient _debug_exception code from entry.S
Only MMU KGDB support is supported.
Signed-off-by: Michal Simek <monstr@monstr.eu>
CC: Jason Wessel <jason.wessel@windriver.com>
CC: John Williams <john.williams@petalogix.com>
CC: Edgar E. Iglesias <edgar.iglesias@petalogix.com>
CC: linux-kernel@vger.kernel.org
Acked-by: Jason Wessel <jason.wessel@windriver.com>
diff --git a/arch/microblaze/kernel/entry.S b/arch/microblaze/kernel/entry.S
index 5a5cb58..304882e 100644
--- a/arch/microblaze/kernel/entry.S
+++ b/arch/microblaze/kernel/entry.S
@@ -745,11 +745,8 @@
nop
/*
- * `Debug' trap
- * We enter dbtrap in "BIP" (breakpoint) mode.
- * So we exit the breakpoint mode with an 'rtbd' and proceed with the
- * original dbtrap.
- * however, wait to save state first
+ * Debug trap for KGDB. Enter to _debug_exception by brki r16, 0x18
+ * and call handling function with saved pt_regs
*/
C_ENTRY(_debug_exception):
/* BIP bit is set on entry, no interrupts can occur */
@@ -759,18 +756,44 @@
nop
andi r1, r1, MSR_UMS
bnei r1, 1f
- /* Kernel-mode state save. */
+/* MS: Kernel-mode state save - kgdb */
lwi r1, r0, TOPHYS(PER_CPU(ENTRY_SP)); /* Reload kernel stack-ptr*/
- tophys(r1,r1);
- addik r1, r1, -STATE_SAVE_SIZE; /* Make room on the stack. */
+ /* BIP bit is set on entry, no interrupts can occur */
+ addik r1, r1, CONFIG_KERNEL_BASE_ADDR - CONFIG_KERNEL_START - STATE_SAVE_SIZE;
SAVE_REGS;
+ /* save all regs to pt_reg structure */
+ swi r0, r1, PTO+PT_R0; /* R0 must be saved too */
+ swi r14, r1, PTO+PT_R14 /* rewrite saved R14 value */
+ swi r16, r1, PTO+PT_R16
+ swi r16, r1, PTO+PT_PC; /* PC and r16 are the same */
+ swi r17, r1, PTO+PT_R17
+ /* save special purpose registers to pt_regs */
+ mfs r11, rear;
+ swi r11, r1, PTO+PT_EAR;
+ mfs r11, resr;
+ swi r11, r1, PTO+PT_ESR;
+ mfs r11, rfsr;
+ swi r11, r1, PTO+PT_FSR;
- swi r1, r1, PTO + PT_MODE;
- brid 2f;
- nop; /* Fill delay slot */
-1: /* User-mode state save. */
- lwi r1, r0, TOPHYS(PER_CPU(CURRENT_SAVE)); /* get saved current */
+ /* stack pointer is in physical address at it is decrease
+ * by STATE_SAVE_SIZE but we need to get correct R1 value */
+ addik r11, r1, CONFIG_KERNEL_START - CONFIG_KERNEL_BASE_ADDR + STATE_SAVE_SIZE;
+ swi r11, r1, PTO+PT_R1
+ /* MS: r31 - current pointer isn't changed */
+ tovirt(r1,r1)
+#ifdef CONFIG_KGDB
+ addi r5, r1, PTO /* pass pt_reg address as the first arg */
+ la r15, r0, dbtrap_call; /* return address */
+ rtbd r0, microblaze_kgdb_break
+ nop;
+#endif
+ /* MS: Place handler for brki from kernel space if KGDB is OFF.
+ * It is very unlikely that another brki instruction is called. */
+ bri 0
+
+/* MS: User-mode state save - gdb */
+1: lwi r1, r0, TOPHYS(PER_CPU(CURRENT_SAVE)); /* get saved current */
tophys(r1,r1);
lwi r1, r1, TS_THREAD_INFO; /* get the thread info */
addik r1, r1, THREAD_SIZE; /* calculate kernel stack pointer */
@@ -781,36 +804,32 @@
swi r17, r1, PTO+PT_R17;
swi r16, r1, PTO+PT_R16;
swi r16, r1, PTO+PT_PC; /* Save LP */
-
swi r0, r1, PTO + PT_MODE; /* Was in user-mode. */
lwi r11, r0, TOPHYS(PER_CPU(ENTRY_SP));
swi r11, r1, PTO+PT_R1; /* Store user SP. */
-2: lwi CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));
+ lwi CURRENT_TASK, r0, TOPHYS(PER_CPU(CURRENT_SAVE));
tovirt(r1,r1)
-
set_vms;
addik r5, r1, PTO;
addik r15, r0, dbtrap_call;
-dbtrap_call: /* return point for kernel/user entry */
+dbtrap_call: /* Return point for kernel/user entry + 8 because of rtsd r15, 8 */
rtbd r0, sw_exception
nop
- set_bip; /* Ints masked for state restore*/
+ /* MS: The first instruction for the second part of the gdb/kgdb */
+ set_bip; /* Ints masked for state restore */
lwi r11, r1, PTO + PT_MODE;
bnei r11, 2f;
-
+/* MS: Return to user space - gdb */
/* Get current task ptr into r11 */
lwi r11, CURRENT_TASK, TS_THREAD_INFO; /* get thread info */
lwi r11, r11, TI_FLAGS; /* get flags in thread info */
andi r11, r11, _TIF_NEED_RESCHED;
beqi r11, 5f;
-/* Call the scheduler before returning from a syscall/trap. */
-
+ /* Call the scheduler before returning from a syscall/trap. */
bralid r15, schedule; /* Call scheduler */
nop; /* delay slot */
- /* XXX Is PT_DTRACE handling needed here? */
- /* XXX m68knommu also checks TASK_STATE & TASK_COUNTER here. */
/* Maybe handle a signal */
5: lwi r11, CURRENT_TASK, TS_THREAD_INFO; /* get thread info */
@@ -818,48 +837,37 @@
andi r11, r11, _TIF_SIGPENDING;
beqi r11, 1f; /* Signals to handle, handle them */
-/* Handle a signal return; Pending signals should be in r18. */
- /* Not all registers are saved by the normal trap/interrupt entry
- points (for instance, call-saved registers (because the normal
- C-compiler calling sequence in the kernel makes sure they're
- preserved), and call-clobbered registers in the case of
- traps), but signal handlers may want to examine or change the
- complete register state. Here we save anything not saved by
- the normal entry sequence, so that it may be safely restored
- (in a possibly modified form) after do_signal returns. */
-
addik r5, r1, PTO; /* Arg 1: struct pt_regs *regs */
addi r7, r0, 0; /* Arg 3: int in_syscall */
bralid r15, do_signal; /* Handle any signals */
add r6, r0, r0; /* Arg 2: sigset_t *oldset */
-
/* Finally, return to user state. */
-1:
- swi CURRENT_TASK, r0, PER_CPU(CURRENT_SAVE); /* save current */
+1: swi CURRENT_TASK, r0, PER_CPU(CURRENT_SAVE); /* save current */
VM_OFF;
tophys(r1,r1);
-
+ /* MS: Restore all regs */
RESTORE_REGS
lwi r17, r1, PTO+PT_R17;
lwi r16, r1, PTO+PT_R16;
- addik r1, r1, STATE_SAVE_SIZE /* Clean up stack space. */
+ addik r1, r1, STATE_SAVE_SIZE /* Clean up stack space */
+ lwi r1, r1, PT_R1 - PT_SIZE; /* Restore user stack pointer */
+DBTRAP_return_user: /* MS: Make global symbol for debugging */
+ rtbd r16, 0; /* MS: Instructions to return from a debug trap */
+ nop;
-
- lwi r1, r1, PT_R1 - PT_SIZE;
- /* Restore user stack pointer. */
- bri 6f;
-
-/* Return to kernel state. */
+/* MS: Return to kernel state - kgdb */
2: VM_OFF;
tophys(r1,r1);
+ /* MS: Restore all regs */
RESTORE_REGS
- addik r1, r1, STATE_SAVE_SIZE /* Clean up stack space. */
-
+ lwi r14, r1, PTO+PT_R14;
+ lwi r16, r1, PTO+PT_PC;
+ lwi r17, r1, PTO+PT_R17;
+ addik r1, r1, STATE_SAVE_SIZE; /* MS: Clean up stack space */
tovirt(r1,r1);
-6:
-DBTRAP_return: /* Make global symbol for debugging */
- rtbd r16, 0; /* Instructions to return from an IRQ */
+DBTRAP_return_kernel: /* MS: Make global symbol for debugging */
+ rtbd r16, 0; /* MS: Instructions to return from a debug trap */
nop;