When calling qemu_system_reset after startup on a Cortex-M CPU, the
initial values of PC, MSP and the Thumb bit weren't set correctly. In
particular, since Thumb was 0, a Usage Fault would arise immediately
after trying to excecute any instruction on a Cortex-M.
Signed-off-by: Martin Galvan <martin.gal...@tallertechnologies.com>
---
Changed since previous version: We're not adding initial_MSP and
initial_PC to the CPU state. Instead, we're loading the initial values
using ldl_phys.
target-arm/cpu.c | 16 ++++++++++++----
1 file changed, 12 insertions(+), 4 deletions(-)
diff --git a/target-arm/cpu.c b/target-arm/cpu.c
index 5ac1bf9..9dfa50e 100644
--- a/target-arm/cpu.c
+++ b/target-arm/cpu.c
@@ -136,14 +136,22 @@ static void arm_cpu_reset(CPUState *s)
env->daif &= ~PSTATE_I;
rom = rom_ptr(0);
if (rom) {
- /* We should really use ldl_phys here, in case the guest
- modified flash and reset itself. However images
- loaded via -kernel have not been copied yet, so load the
- values directly from there. */
+ /* Address zero is covered by ROM which hasn't yet been
+ copied into physical memory. */
env->regs[13] = ldl_p(rom) & 0xFFFFFFFC;
pc = ldl_p(rom + 4);
env->thumb = pc & 1;
env->regs[15] = pc & ~1;
+ } else {
+ /* Address zero not covered by a ROM blob, or the ROM blob
+ is in non-modifiable memory and this is a second reset after
+ it got copied into memory. In the latter case, rom_ptr
will return
+ a NULL pointer and we should use ldl_phys instead.
+ */
+ env->regs[13] = ldl_phys(s->as, 0) & 0xFFFFFFFC;
+ pc = ldl_phys(s->as, 4);
+ env->thumb = pc & 1;
+ env->regs[15] = pc & ~1;
}
}
--
1.9.1
--
Martín Galván
Software Engineer
Taller Technologies Argentina
San Lorenzo 47, 3rd Floor, Office 5
Córdoba, Argentina
Phone: 54 351 4217888 / +54 351 4218211
