Re: [Qemu-devel] [PATCH] arm: fix arm kernel boot for non zero start addr

[Lars Munch <lars@segv.dk>]

On Sat, May 29, 2010 at 8:51 PM, Aurelien Jarno <aurelien@aurel32.net> wrote:
> On Sat, May 29, 2010 at 08:42:52PM +0200, Lars Munch wrote:
>> On Fri, May 28, 2010 at 9:24 PM, Aurelien Jarno <aurelien@aurel32.net> wrote:
>> > On Sat, May 08, 2010 at 10:43:35PM +0200, Lars Munch wrote:
>> >> Booting an arm kernel has been broken a while when booting from non zero start
>> >> address. This is due to the order of events: board init loads the kernel and
>> >> sets register 15 to the start address and then qemu_system_reset reset the cpu
>> >> making register 15 zero again.
>> >>
>> >> This patch fixes the usage of the register 15 start address trick in
>> >> combination with arm_load_kernel.
>> >>
>> >> Signed-off-by: Lars Munch <lars@segv.dk>
>> >> ---
>> >>  hw/arm_boot.c       |    1 +
>> >>  hw/gumstix.c        |    4 ----
>> >>  hw/mainstone.c      |    3 ---
>> >>  hw/nseries.c        |    7 -------
>> >>  hw/omap_sx1.c       |    5 -----
>> >>  hw/palm.c           |    4 ----
>> >>  hw/spitz.c          |    3 ---
>> >>  hw/tosa.c           |    3 ---
>> >>  target-arm/helper.c |    1 -
>> >>  9 files changed, 1 insertions(+), 30 deletions(-)
>> >>
>> >> diff --git a/hw/arm_boot.c b/hw/arm_boot.c
>> >> index df031a5..620550b 100644
>> >> --- a/hw/arm_boot.c
>> >> +++ b/hw/arm_boot.c
>> >> @@ -187,6 +187,7 @@ static void main_cpu_reset(void *opaque)
>> >>              env->regs[15] = info->entry & 0xfffffffe;
>> >>              env->thumb = info->entry & 1;
>> >>          } else {
>> >> +            env->regs[15] = info->loader_start;
>> >>              if (old_param) {
>> >>                  set_kernel_args_old(info, info->initrd_size,
>> >>                                      info->loader_start);
>> >
>> > This parts looks fine.
>> >
>> >> diff --git a/hw/gumstix.c b/hw/gumstix.c
>> >> index 3fd31f4..b64e04e 100644
>> >> --- a/hw/gumstix.c
>> >> +++ b/hw/gumstix.c
>> >> @@ -74,8 +74,6 @@ static void connex_init(ram_addr_t ram_size,
>> >>          exit(1);
>> >>      }
>> >>
>> >> -    cpu->env->regs[15] = 0x00000000;
>> >> -
>> >>      /* Interrupt line of NIC is connected to GPIO line 36 */
>> >>      smc91c111_init(&nd_table[0], 0x04000300,
>> >>                      pxa2xx_gpio_in_get(cpu->gpio)[36]);
>> >> @@ -114,8 +112,6 @@ static void verdex_init(ram_addr_t ram_size,
>> >>          exit(1);
>> >>      }
>> >>
>> >> -    cpu->env->regs[15] = 0x00000000;
>> >> -
>> >>      /* Interrupt line of NIC is connected to GPIO line 99 */
>> >>      smc91c111_init(&nd_table[0], 0x04000300,
>> >>                      pxa2xx_gpio_in_get(cpu->gpio)[99]);
>> >> diff --git a/hw/mainstone.c b/hw/mainstone.c
>> >> index a4379e3..54bacfb 100644
>> >> --- a/hw/mainstone.c
>> >> +++ b/hw/mainstone.c
>> >> @@ -89,9 +89,6 @@ static void mainstone_common_init(ram_addr_t ram_size,
>> >>      cpu_register_physical_memory(0, MAINSTONE_ROM,
>> >>                      qemu_ram_alloc(MAINSTONE_ROM) | IO_MEM_ROM);
>> >>
>> >> -    /* Setup initial (reset) machine state */
>> >> -    cpu->env->regs[15] = mainstone_binfo.loader_start;
>> >> -
>> >>  #ifdef TARGET_WORDS_BIGENDIAN
>> >>      be = 1;
>> >>  #else
>> >> diff --git a/hw/nseries.c b/hw/nseries.c
>> >> index 0273eee..04a028d 100644
>> >> --- a/hw/nseries.c
>> >> +++ b/hw/nseries.c
>> >> @@ -1016,7 +1016,6 @@ static void n8x0_boot_init(void *opaque)
>> >>      n800_dss_init(&s->blizzard);
>> >>
>> >>      /* CPU setup */
>> >> -    s->cpu->env->regs[15] = s->cpu->env->boot_info->loader_start;
>> >>      s->cpu->env->GE = 0x5;
>> >>
>> >>      /* If the machine has a slided keyboard, open it */
>> >> @@ -1317,11 +1316,6 @@ static void n8x0_init(ram_addr_t ram_size, const char *boot_device,
>> >>      if (usb_enabled)
>> >>          n8x0_usb_setup(s);
>> >>
>> >> -    /* Setup initial (reset) machine state */
>> >> -
>> >> -    /* Start at the OneNAND bootloader.  */
>> >> -    s->cpu->env->regs[15] = 0;
>> >> -
>> >>      if (kernel_filename) {
>> >>          /* Or at the linux loader.  */
>> >>          binfo->kernel_filename = kernel_filename;
>> >> @@ -1330,7 +1324,6 @@ static void n8x0_init(ram_addr_t ram_size, const char *boot_device,
>> >>          arm_load_kernel(s->cpu->env, binfo);
>> >>
>> >>          qemu_register_reset(n8x0_boot_init, s);
>> >> -        n8x0_boot_init(s);
>> >>      }
>> >>
>> >>      if (option_rom[0] && (boot_device[0] == 'n' || !kernel_filename)) {
>> >> diff --git a/hw/omap_sx1.c b/hw/omap_sx1.c
>> >> index ca0a7d1..2e9879f 100644
>> >> --- a/hw/omap_sx1.c
>> >> +++ b/hw/omap_sx1.c
>> >> @@ -195,15 +195,10 @@ static void sx1_init(ram_addr_t ram_size,
>> >>
>> >>      /* Load the kernel.  */
>> >>      if (kernel_filename) {
>> >> -        /* Start at bootloader.  */
>> >> -        cpu->env->regs[15] = sx1_binfo.loader_start;
>> >> -
>> >>          sx1_binfo.kernel_filename = kernel_filename;
>> >>          sx1_binfo.kernel_cmdline = kernel_cmdline;
>> >>          sx1_binfo.initrd_filename = initrd_filename;
>> >>          arm_load_kernel(cpu->env, &sx1_binfo);
>> >> -    } else {
>> >> -        cpu->env->regs[15] = 0x00000000;
>> >>      }
>> >>
>> >>      /* TODO: fix next line */
>> >> diff --git a/hw/palm.c b/hw/palm.c
>> >> index ba7c398..8db133d 100644
>> >> --- a/hw/palm.c
>> >> +++ b/hw/palm.c
>> >> @@ -243,7 +243,6 @@ static void palmte_init(ram_addr_t ram_size,
>> >>              rom_size = load_image_targphys(option_rom[0], OMAP_CS0_BASE,
>> >>                                             flash_size);
>> >>              rom_loaded = 1;
>> >> -            cpu->env->regs[15] = 0x00000000;
>> >>          }
>> >>          if (rom_size < 0) {
>> >>              fprintf(stderr, "%s: error loading '%s'\n",
>> >> @@ -258,9 +257,6 @@ static void palmte_init(ram_addr_t ram_size,
>> >>
>> >>      /* Load the kernel.  */
>> >>      if (kernel_filename) {
>> >> -        /* Start at bootloader.  */
>> >> -        cpu->env->regs[15] = palmte_binfo.loader_start;
>> >> -
>> >>          palmte_binfo.kernel_filename = kernel_filename;
>> >>          palmte_binfo.kernel_cmdline = kernel_cmdline;
>> >>          palmte_binfo.initrd_filename = initrd_filename;
>> >> diff --git a/hw/spitz.c b/hw/spitz.c
>> >> index c3b5cd8..4f82e24 100644
>> >> --- a/hw/spitz.c
>> >> +++ b/hw/spitz.c
>> >> @@ -993,9 +993,6 @@ static void spitz_common_init(ram_addr_t ram_size,
>> >>          /* A 4.0 GB microdrive is permanently sitting in CF slot 0.  */
>> >>          spitz_microdrive_attach(cpu, 0);
>> >>
>> >> -    /* Setup initial (reset) machine state */
>> >> -    cpu->env->regs[15] = spitz_binfo.loader_start;
>> >> -
>> >>      spitz_binfo.kernel_filename = kernel_filename;
>> >>      spitz_binfo.kernel_cmdline = kernel_cmdline;
>> >>      spitz_binfo.initrd_filename = initrd_filename;
>> >> diff --git a/hw/tosa.c b/hw/tosa.c
>> >> index bc6591f..fbe8d8c 100644
>> >> --- a/hw/tosa.c
>> >> +++ b/hw/tosa.c
>> >> @@ -229,9 +229,6 @@ static void tosa_init(ram_addr_t ram_size,
>> >>
>> >>      tosa_tg_init(cpu);
>> >>
>> >> -    /* Setup initial (reset) machine state */
>> >> -    cpu->env->regs[15] = tosa_binfo.loader_start;
>> >> -
>> >>      tosa_binfo.kernel_filename = kernel_filename;
>> >>      tosa_binfo.kernel_cmdline = kernel_cmdline;
>> >>      tosa_binfo.initrd_filename = initrd_filename;
>> >> diff --git a/target-arm/helper.c b/target-arm/helper.c
>> >> index 99e0394..63e5dc7 100644
>> >> --- a/target-arm/helper.c
>> >> +++ b/target-arm/helper.c
>> >> @@ -207,7 +207,6 @@ void cpu_reset(CPUARMState *env)
>> >>  #else
>> >>      /* SVC mode with interrupts disabled.  */
>> >>      env->uncached_cpsr = ARM_CPU_MODE_SVC | CPSR_A | CPSR_F | CPSR_I;
>> >> -    env->regs[15] = 0;
>> >>      /* On ARMv7-M the CPSR_I is the value of the PRIMASK register, and is
>> >>         clear at reset.  Initial SP and PC are loaded from ROM.  */
>> >>      if (IS_M(env)) {
>> >
>> > This part doesn't. The register reset should be kept in case in case the
>> > test "if (info)" in main_cpu_reset() is false.
>>
>> All the "regs[15] = xyz" above are unneeded now as they are all used
>> in combination with arm_boot_kernel with a valid info struct.
>
> Agreed.
>
>> The last "env->regs[15] = 0" is redundant as the register is already
>> zeroed at that point.
>>
>
> Where is it zeroed?

In this memset(env, 0, offsetof(CPUARMState, breakpoints)); in
cpu_reset (line 201 in target-arm/helper.c)