GRMON3-UM
June 2019, Version 3.1.0
30 www.cobham.com/gaisler
(gdb) symbol-file output/images/image
Reading symbols from /home/user/linuxbuild-1.0.2/output/images/image...done.
(gdb) target extended-remote :2222
Remote debugging using :2222
t_tflt () at /home/user/linuxbuild-1.0.2/linux/linux-2.6-git/arch/sparc/kernel/h
ead_32.S:88
88 t_tflt: SPARC_TFAULT /* Inst. Access Exception
*/
Current language: auto; currently asm
(gdb) load
Loading section .text, size 0x10b0 lma 0x40000000
Loading section .data, size 0x50 lma 0x400010b0
Loading section .vmlinux, size 0x3f1a60 lma 0x40004000
Loading section .startup_prom, size 0x7ee0 lma 0x403f5a60
Start address 0x40000000, load size 4172352
Transfer rate: 18 KB/sec, 765 bytes/write.
The program must reach a state where the MMU is enabled before any virtual address can be translated. Software
breakpoints cannot be used since the MMU is still disabled and GRMON won't translate them into a physical.
Hardware breakpoints don't need to be translated into physical addresses, therefore set a hardware assisted break-
point at 0xf0004000, which is the virtual start address for the Linux kernel.
(gdb) hbreak *0xf0004000
Hardware assisted breakpoint 1 at 0xf0004000: file /home/user/linuxbuild-1.0.2/l
inux/linux-2.6-git/arch/sparc/kernel/head_32.S, line 87.
(gdb) cont
Continuing.
Breakpoint 1, trapbase_cpu0 () at /home/user/linuxbuild-1.0.2/linux/linux-2.6-gi
t/arch/sparc/kernel/head_32.S:87
87 t_zero: b gokernel; nop; nop; nop;
At this point the loader has enabled the MMU and both software breakpoints and symbols can be used.
(gdb) break leon_init_timers
Breakpoint 2 at 0xf03cff14: file /home/user/linuxbuild-1.0.2/linux/linux-2.6-git
/arch/sparc/kernel/leon_kernel.c, line 116.
(gdb) cont
Continuing.
Breakpoint 2, leon_init_timers (counter_fn=0xf00180c8 <timer_interrupt>)
at /home/user/linuxbuild-1.0.2/linux/linux-2.6-git/arch/sparc/kernel/leon_ke
rnel.c:116
116 leondebug_irq_disable = 0;
Current language: auto; currently c
(gdb) bt
#0 leon_init_timers (counter_fn=0xf00180c8 <timer_interrupt>)
at /home/user/linuxbuild-1.0.2/linux/linux-2.6-git/arch/sparc/kernel/leon_ke
rnel.c:116
#1 0xf03ce944 in time_init () at /home/user/linuxbuild-1.0.2/linux/linux-2.6-gi
t/arch/sparc/kernel/time_32.c:227
#2 0xf03cc13c in start_kernel () at /home/user/linuxbuild-1.0.2/linux/linux-2.6
-git/init/main.c:619
#3 0xf03cb804 in sun4c_continue_boot ()
#4 0xf03cb804 in sun4c_continue_boot ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb) info locals
eirq = <value optimized out>
rootnp = <value optimized out>
np = <value optimized out>
pp = <value optimized out>
len = 13
ampopts = <value optimized out>
(gdb) print len
$2 = 13
If the application for some reason need to be reloaded, then the MMU must first be disabled via GRMON. In
addition all software breakpoints should be deleted before the application is restarted since the MMU has been
disabled and GRMON won't translate virtual addresses anymore.
(gdb) mon mmu mctrl 0
mctrl: 006E0000 ctx: 00000000 ctxptr: 40440800 fsr: 00000000 far: 00000000
(gdb) load
Loading section .text, size 0x10b0 lma 0x40000000
Loading section .data, size 0x50 lma 0x400010b0
Loading section .vmlinux, size 0x3f1a60 lma 0x40004000
Loading section .startup_prom, size 0x7ee0 lma 0x403f5a60
Start address 0x40000000, load size 4172352
Transfer rate: 18 KB/sec, 765 bytes/write.
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