Re: [PATCH v4] arm64: Add purgatory printing

[Matthias Brugger <mbrugger@suse.com>]

Hi,

On 02/10/2020 20:34, Bhupesh Sharma wrote:
> Hello Matthias,
> 
> Thanks for the updated revision.
> 
> On Fri, Oct 2, 2020 at 7:13 PM <matthias.bgg@kernel.org> wrote:
>>
>> From: Matthias Brugger <mbrugger@suse.com>
>>
>> Add option to allow purgatory printing on arm64 hardware
>> by passing the console name which should be used.
>> Based on a patch by Geoff Levand.
>>
>> Cc: Geoff Levand <geoff@infradead.org>
>> Signed-off-by: Matthias Brugger <mbrugger@suse.com>
>>
>> ---
>>
>> Changes in v4:
>> - fix snprintf error handling
>>
>> Changes in v3:
>> - check return value of snprintf
>>
>> Changes in v2:
>> - use sizeof(buffer)
>> - user serial command option instead of console
>> - reduce buffer to size 10
>> - use snprintf
>> - fix error handling for wrong serial console parameter
>> - Update help information
>>
>>   kexec/arch/arm64/include/arch/options.h |  6 ++-
>>   kexec/arch/arm64/kexec-arm64.c          | 71 +++++++++++++++++++++++++
>>   purgatory/arch/arm64/purgatory-arm64.c  | 17 +++++-
>>   3 files changed, 92 insertions(+), 2 deletions(-)
>>
>> diff --git a/kexec/arch/arm64/include/arch/options.h b/kexec/arch/arm64/include/arch/options.h
>> index a17d933..8c695f3 100644
>> --- a/kexec/arch/arm64/include/arch/options.h
>> +++ b/kexec/arch/arm64/include/arch/options.h
>> @@ -5,7 +5,8 @@
>>   #define OPT_DTB                        ((OPT_MAX)+1)
>>   #define OPT_INITRD             ((OPT_MAX)+2)
>>   #define OPT_REUSE_CMDLINE      ((OPT_MAX)+3)
>> -#define OPT_ARCH_MAX           ((OPT_MAX)+4)
>> +#define OPT_SERIAL             ((OPT_MAX)+4)
>> +#define OPT_ARCH_MAX           ((OPT_MAX)+5)
>>
>>   #define KEXEC_ARCH_OPTIONS \
>>          KEXEC_OPTIONS \
>> @@ -13,6 +14,7 @@
>>          { "command-line",  1, NULL, OPT_APPEND }, \
>>          { "dtb",           1, NULL, OPT_DTB }, \
>>          { "initrd",        1, NULL, OPT_INITRD }, \
>> +       { "serial",        1, NULL, OPT_SERIAL }, \
>>          { "ramdisk",       1, NULL, OPT_INITRD }, \
>>          { "reuse-cmdline", 0, NULL, OPT_REUSE_CMDLINE }, \
>>
>> @@ -25,6 +27,7 @@ static const char arm64_opts_usage[] __attribute__ ((unused)) =
>>   "     --command-line=STRING Set the kernel command line to STRING.\n"
>>   "     --dtb=FILE            Use FILE as the device tree blob.\n"
>>   "     --initrd=FILE         Use FILE as the kernel initial ramdisk.\n"
>> +"     --serial=STRING       Name of console used for purgatory printing. (e.g. ttyAMA0)\n"
>>   "     --ramdisk=FILE        Use FILE as the kernel initial ramdisk.\n"
>>   "     --reuse-cmdline       Use kernel command line from running system.\n";
>>
>> @@ -32,6 +35,7 @@ struct arm64_opts {
>>          const char *command_line;
>>          const char *dtb;
>>          const char *initrd;
>> +       const char *console;
>>   };
>>
>>   extern struct arm64_opts arm64_opts;
>> diff --git a/kexec/arch/arm64/kexec-arm64.c b/kexec/arch/arm64/kexec-arm64.c
>> index 45ebc54..6f572ed 100644
>> --- a/kexec/arch/arm64/kexec-arm64.c
>> +++ b/kexec/arch/arm64/kexec-arm64.c
>> @@ -165,6 +165,8 @@ int arch_process_options(int argc, char **argv)
>>                          break;
>>                  case OPT_KEXEC_FILE_SYSCALL:
>>                          do_kexec_file_syscall = 1;
>> +               case OPT_SERIAL:
>> +                       arm64_opts.console = optarg;
>>                          break;
>>                  default:
>>                          break; /* Ignore core and unknown options. */
>> @@ -180,12 +182,72 @@ int arch_process_options(int argc, char **argv)
>>          dbgprintf("%s:%d: dtb: %s\n", __func__, __LINE__,
>>                  (do_kexec_file_syscall && arm64_opts.dtb ? "(ignored)" :
>>                                                          arm64_opts.dtb));
>> +       dbgprintf("%s:%d: console: %s\n", __func__, __LINE__,
>> +               arm64_opts.console);
>> +
>>          if (do_kexec_file_syscall)
>>                  arm64_opts.dtb = NULL;
>>
>>          return 0;
>>   }
>>
>> +/**
>> + * find_purgatory_sink - Find a sink for purgatory output.
>> + */
>> +
>> +static uint64_t find_purgatory_sink(const char *console)
>> +{
>> +       int fd, ret;
>> +       char device[255], mem[255];
>> +       struct stat sb;
>> +       char buffer[10];
>> +       uint64_t iomem = 0x0;
>> +
>> +       if (!console)
>> +               return 0;
>> +
>> +       ret = snprintf(device, sizeof(device), "/sys/class/tty/%s", console);
>> +       if (ret < 0 || ret >= sizeof(device)) {
>> +               fprintf(stderr, "snprintf failed: %s\n", strerror(errno));
>> +               return 0;
>> +       }
>> +
>> +       if (stat(device, &sb) || !S_ISDIR(sb.st_mode)) {
>> +               fprintf(stderr, "kexec: %s: No valid console found for %s\n",
>> +                       __func__, device);
>> +               return 0;
>> +       }
>> +
>> +       ret = snprintf(mem, sizeof(mem), "%s%s", device, "/iomem_base");
>> +       if (ret < 0 || ret >= sizeof(mem)) {
>> +               fprintf(stderr, "snprintf failed: %s\n", strerror(errno));
>> +               return 0;
>> +       }
>> +
>> +       printf("console memory read from %s\n", mem);
>> +
>> +       fd = open(mem, O_RDONLY);
>> +       if (fd < 0) {
>> +               fprintf(stderr, "kexec: %s: No able to open %s\n",
>> +                       __func__, mem);
>> +               return 0;
>> +       }
>> +
>> +       memset(buffer, '\0', sizeof(buffer));
>> +       ret = read(fd, buffer, sizeof(buffer));
>> +       if (ret < 0) {
>> +               fprintf(stderr, "kexec: %s: not able to read fd\n", __func__);
>> +               close(fd);
>> +               return 0;
>> +       }
>> +
>> +       sscanf(buffer, "%lx", &iomem);
>> +       printf("console memory is at %#lx\n", iomem);
>> +
>> +       close(fd);
>> +       return iomem;
>> +}
>> +
>>   /**
>>    * struct dtb - Info about a binary device tree.
>>    *
>> @@ -637,6 +699,7 @@ int arm64_load_other_segments(struct kexec_info *info,
>>          unsigned long hole_min;
>>          unsigned long hole_max;
>>          unsigned long initrd_end;
>> +       uint64_t purgatory_sink;
>>          char *initrd_buf = NULL;
>>          struct dtb dtb;
>>          char command_line[COMMAND_LINE_SIZE] = "";
>> @@ -654,6 +717,11 @@ int arm64_load_other_segments(struct kexec_info *info,
>>                  command_line[sizeof(command_line) - 1] = 0;
>>          }
>>
>> +       purgatory_sink = find_purgatory_sink(arm64_opts.console);
>> +
>> +       dbgprintf("%s:%d: purgatory sink: 0x%" PRIx64 "\n", __func__, __LINE__,
>> +               purgatory_sink);
>> +
>>          if (arm64_opts.dtb) {
>>                  dtb.name = "dtb_user";
>>                  dtb.buf = slurp_file(arm64_opts.dtb, &dtb.size);
>> @@ -742,6 +810,9 @@ int arm64_load_other_segments(struct kexec_info *info,
>>
>>          info->entry = (void *)elf_rel_get_addr(&info->rhdr, "purgatory_start");
>>
>> +       elf_rel_set_symbol(&info->rhdr, "arm64_sink", &purgatory_sink,
>> +               sizeof(purgatory_sink));
>> +
>>          elf_rel_set_symbol(&info->rhdr, "arm64_kernel_entry", &image_base,
>>                  sizeof(image_base));
>>
>> diff --git a/purgatory/arch/arm64/purgatory-arm64.c b/purgatory/arch/arm64/purgatory-arm64.c
>> index fe50fcf..b4d8578 100644
>> --- a/purgatory/arch/arm64/purgatory-arm64.c
>> +++ b/purgatory/arch/arm64/purgatory-arm64.c
>> @@ -5,15 +5,30 @@
>>   #include <stdint.h>
>>   #include <purgatory.h>
>>
>> +/* Symbols set by kexec. */
>> +
>> +uint8_t *arm64_sink __attribute__ ((section ("data")));
>> +extern void (*arm64_kernel_entry)(uint64_t, uint64_t, uint64_t, uint64_t);
>> +extern uint64_t arm64_dtb_addr;
>> +
>>   void putchar(int ch)
>>   {
>> -       /* Nothing for now */
>> +       if (!arm64_sink)
>> +               return;
>> +
>> +       *arm64_sink = ch;
>> +
>> +       if (ch == '\n')
>> +               *arm64_sink = '\r';
>>   }
>>
>>   void post_verification_setup_arch(void)
>>   {
>> +       printf("purgatory: booting kernel now\n");
>>   }
>>
>>   void setup_arch(void)
>>   {
>> +       printf("purgatory: entry=%lx\n", (unsigned long)arm64_kernel_entry);
>> +       printf("purgatory: dtb=%lx\n", arm64_dtb_addr);
>>   }
>> --
>> 2.28.0
> 
> Looks good to me, so:
> Acked-by: Bhupesh Sharma <bhsharma@redhat.com>
> 

Simon: friendly reminder of this patch. Please let me know if you have any 
concerns regarding the patch.

Best regards,
Matthias

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