Re: [Qemu-devel] [PATCH 4/4] target-arm: add minimal dump-guest-memory support

[Peter Maydell]

On 20 June 2012 18:28, Rabin Vincent <address@hidden> wrote:
> Add a minimal dump-guest-memory support for ARM.  The -p option is not
> supported and we don't add any QEMU-specific notes.

So what does this patch give us? This commit message is pretty
short and I couldn't find a cover message for the patchset...

> Signed-off-by: Rabin Vincent <address@hidden>
> ---
>  configure                        |    4 +--
>  target-arm/Makefile.objs         |    2 +-
>  target-arm/arch_dump.c           |   59 
> ++++++++++++++++++++++++++++++++++++++
>  target-arm/arch_memory_mapping.c |   13 +++++++++
>  4 files changed, 75 insertions(+), 3 deletions(-)
>  create mode 100644 target-arm/arch_dump.c
>  create mode 100644 target-arm/arch_memory_mapping.c
>
> diff --git a/configure b/configure
> index b68c0ca..a20ad19 100755
> --- a/configure
> +++ b/configure
> @@ -3727,7 +3727,7 @@ case "$target_arch2" in
>     fi
>  esac
>  case "$target_arch2" in
> -  i386|x86_64)
> +  arm|i386|x86_64)
>     echo "CONFIG_HAVE_GET_MEMORY_MAPPING=y" >> $config_target_mak
>  esac
>  if test "$target_arch2" = "ppc64" -a "$fdt" = "yes"; then
> @@ -3746,7 +3746,7 @@ if test "$target_softmmu" = "yes" ; then
>     echo "subdir-$target: subdir-libcacard" >> $config_host_mak
>   fi
>   case "$target_arch2" in
> -    i386|x86_64)
> +    arm|i386|x86_64)
>       echo "CONFIG_HAVE_CORE_DUMP=y" >> $config_target_mak
>   esac
>  fi
> diff --git a/target-arm/Makefile.objs b/target-arm/Makefile.objs
> index f447c4f..837b374 100644
> --- a/target-arm/Makefile.objs
> +++ b/target-arm/Makefile.objs
> @@ -1,5 +1,5 @@
>  obj-y += arm-semi.o
> -obj-$(CONFIG_SOFTMMU) += machine.o
> +obj-$(CONFIG_SOFTMMU) += machine.o arch_memory_mapping.o arch_dump.o
>  obj-y += translate.o op_helper.o helper.o cpu.o
>  obj-y += neon_helper.o iwmmxt_helper.o
>
> diff --git a/target-arm/arch_dump.c b/target-arm/arch_dump.c
> new file mode 100644
> index 0000000..47a7e40
> --- /dev/null
> +++ b/target-arm/arch_dump.c
> @@ -0,0 +1,59 @@
> +#include "cpu.h"
> +#include "cpu-all.h"
> +#include "dump.h"
> +#include "elf.h"
> +
> +typedef struct {
> +    char pad1[24];
> +    uint32_t pid;
> +    char pad2[44];
> +    uint32_t regs[18];
> +    char pad3[4];
> +} arm_elf_prstatus;

I'm guessing this is following some specification's structure layout;
what specification?

> +
> +int cpu_write_elf64_note(write_core_dump_function f, CPUArchState *env,
> +                         int cpuid, void *opaque)

Should these APIs really be taking a CPUArchState* rather rather than
an ARMCPU* ? (Andreas?)

> +{
> +    return -1;
> +}
> +
> +int cpu_write_elf32_note(write_core_dump_function f, CPUArchState *env,
> +                         int cpuid, void *opaque)
> +{
> +    arm_elf_prstatus prstatus;
> +
> +    memset(&prstatus, 0, sizeof(prstatus));
> +    memcpy(&(prstatus.regs), env->regs, sizeof(env->regs));

This looks a bit odd -- env->regs[] is a 16 word array but
prstatus.regs is 18 words. What are the last two words for?

> +    prstatus.pid = cpuid;
> +
> +    return dump_write_elf_note(ELFCLASS32, "CORE", NT_PRSTATUS,
> +                               &prstatus, sizeof(prstatus),
> +                               f, opaque);
> +}
> +
> +int cpu_write_elf64_qemunote(write_core_dump_function f, CPUArchState *env,
> +                             void *opaque)
> +{
> +    return -1;
> +}
> +
> +int cpu_write_elf32_qemunote(write_core_dump_function f, CPUArchState *env,
> +                             void *opaque)
> +{
> +    return 0;
> +}
> +
> +int cpu_get_dump_info(ArchDumpInfo *info)
> +{
> +    info->d_machine = EM_ARM;
> +    info->d_endian = ELFDATA2LSB;

...even for big endian ARM?

> +    info->d_class = ELFCLASS32;
> +
> +    return 0;
> +}
> +
> +ssize_t cpu_get_note_size(int class, int machine, int nr_cpus)
> +{
> +    return nr_cpus * dump_get_note_size(ELFCLASS32, "CORE",
> +                                        sizeof(arm_elf_prstatus));
> +}
> diff --git a/target-arm/arch_memory_mapping.c 
> b/target-arm/arch_memory_mapping.c
> new file mode 100644
> index 0000000..eeaaf09
> --- /dev/null
> +++ b/target-arm/arch_memory_mapping.c
> @@ -0,0 +1,13 @@
> +#include "cpu.h"
> +#include "cpu-all.h"
> +#include "memory_mapping.h"
> +
> +bool cpu_paging_enabled(CPUArchState *env)
> +{
> +    return 0;
> +}
> +
> +int cpu_get_memory_mapping(MemoryMappingList *list, CPUArchState *env)
> +{
> +    return -1;
> +}

Why do we need these null implementations and why do they
work better than the default ones in memory_mapping-stub.c ?

(memory_mapping.h could use some documentation comments
describing the purpose and API of these functions IMHO.)

-- PMM