Hi lianbo,

This patch LGTM, but I'm unsure if this patch has relations with the
ppc64 bug: 
https://www.mail-archive.com/[email protected]/msg01649.html.
So I will leave it here and merge after the ppc64 bug is resolved.

Thanks,
Tao Liu

On Thu, Sep 18, 2025 at 3:22 PM lijiang <[email protected]> wrote:
>
> On Thu, Sep 18, 2025 at 9:50 AM HAGIO KAZUHITO(萩尾 一仁) <[email protected]> 
> wrote:
>>
>> On 2025/09/17 23:15, Lianbo Jiang wrote:
>> > Currently, the log command will display human readable Rust
>> > symbol name by default if any, but, sometimes still want to
>> > print the original messages from the log buffer(do not demangle).
>> >
>> > In addition, if the log buffer has lines like "_R ... +" which
>> > are not Rust symbols unexpectedly, probably the output will be
>> > missed, that is unexpected.
>> >
>> > To fix above cases, add "log -R" to display human readable Rust
>> > symbol name, otherwise still print the original messages.
>> >
>> > With the patch:
>> >    crash> log -R
>> >    ...
>> >    [ 2174.289360] Tainted: [S]=CPU_OUT_OF_SPEC, [O]=OOT_MODULE, 
>> > [E]=UNSIGNED_MODULE
>> >    [ 2174.297322] Hardware name: Intel Corporation S2600CWR/S2600CWR, BIOS 
>> > SE5C610.86B.01.01.0018.072020161249 07/20/2016
>> >    [ 2174.308966] Call Trace:
>> >    [ 2174.311693]  <TASK>
>> >    [ 2174.314033]  dump_stack_lvl+0x5d/0x80
>> >    [ 2174.318125]  panic+0x156/0x32a
>> >    [ 2174.321539]  rust_panic::area_in_hp+0xf7/0x120 [rust_panic]
>> >    [ 2174.329700]  ? console_unlock+0x9c/0x140
>> >    [ 2174.334080]  ? irq_work_queue+0x2d/0x50
>> >    [ 2174.338352]  ? __pfx_init_module+0x10/0x10 [rust_panic]
>> >    [ 2174.344183]  <rust_panic::HelloPanic>::step_two+0x20/0xe0 
>> > [rust_panic]
>> >    [ 2174.353698]  ? _printk+0x6b/0x90
>> >    [ 2174.357303]  init_module+0x57/0xff0 [rust_panic]
>> >    [ 2174.362456]  ? __pfx_init_module+0x10/0x10 [rust_panic]
>> >    ...
>> >
>> > Suggested-by: Kazuhito Hagio <[email protected]>
>> > Signed-off-by: Lianbo Jiang <[email protected]>
>>
>> Thank you for the patch, Lianbo.  It looks good to me and cleans my worries.
>>
>
> Np. This looks better to me.
>
> Lianbo
>
>>
>> Thanks,
>> Kazu
>>
>> > ---
>> >   defs.h   |  1 +
>> >   help.c   | 24 +++++++++++++++++++++++-
>> >   kernel.c |  5 ++++-
>> >   printk.c | 53 +++++++++++++++++++++++++++++------------------------
>> >   4 files changed, 57 insertions(+), 26 deletions(-)
>> >
>> > diff --git a/defs.h b/defs.h
>> > index 156ac0232906..997145cba9d2 100644
>> > --- a/defs.h
>> > +++ b/defs.h
>> > @@ -6227,6 +6227,7 @@ void parse_kernel_version(char *);
>> >   #define SHOW_LOG_CTIME   (0x10)
>> >   #define SHOW_LOG_SAFE    (0x20)
>> >   #define SHOW_LOG_CALLER  (0x40)
>> > +#define SHOW_LOG_RUST    (0x80)
>> >   void set_cpu(int);
>> >   void clear_machdep_cache(void);
>> >   struct stack_hook *gather_text_list(struct bt_info *);
>> > diff --git a/help.c b/help.c
>> > index 4f071e0bd0a0..78d7a5c70e30 100644
>> > --- a/help.c
>> > +++ b/help.c
>> > @@ -4026,7 +4026,7 @@ NULL
>> >   char *help_log[] = {
>> >   "log",
>> >   "dump system message buffer",
>> > -"[-Ttdmasc]",
>> > +"[-TtdmascR]",
>> >   "  This command dumps the kernel log_buf contents in chronological 
>> > order.  The",
>> >   "  command supports the older log_buf formats, which may or may not 
>> > contain a",
>> >   "  timestamp inserted prior to each message, as well as the newer 
>> > variable-length",
>> > @@ -4053,6 +4053,8 @@ char *help_log[] = {
>> >   "        the CPU id (if in CPU context) that called printk(), if 
>> > available.",
>> >   "        Generally available on Linux 5.1 to 5.9 kernels configured 
>> > with",
>> >   "        CONFIG_PRINTK_CALLER or Linux 5.10 and later kernels.",
>> > +"    -R  Display the message text with human readable Rust symbol name if 
>> > any,",
>> > +"        otherwise still print the original message text.",
>> >   " ",
>> >   "\nEXAMPLES",
>> >   "  Dump the kernel message buffer:\n",
>> > @@ -4231,6 +4233,26 @@ char *help_log[] = {
>> >   "    [    0.014179] [    T29] RAMDISK: [mem 0x3cf4f000-0x437bbfff]",
>> >   "    [    0.198789] [     C0] DMAR: DRHD: handling fault status reg 3",
>> >   "    ...",
>> > +" ",
>> > +"  Display the message text with human readable Rust symbol name if any,",
>> > +"  otherwise still print the original message text.\n",
>> > +"    %s> log -R",
>> > +"    ...",
>> > +"    [ 2174.289360] Tainted: [S]=CPU_OUT_OF_SPEC, [O]=OOT_MODULE, 
>> > [E]=UNSIGNED_MODULE",
>> > +"    [ 2174.297322] Hardware name: Intel Corporation S2600CWR/S2600CWR, 
>> > BIOS SE5C610.86B.01.01.0018.072020161249 07/20/2016",
>> > +"    [ 2174.308966] Call Trace:",
>> > +"    [ 2174.311693]  <TASK>",
>> > +"    [ 2174.314033]  dump_stack_lvl+0x5d/0x80",
>> > +"    [ 2174.318125]  panic+0x156/0x32a",
>> > +"    [ 2174.321539]  rust_panic::area_in_hp+0xf7/0x120 [rust_panic]",
>> > +"    [ 2174.329700]  ? console_unlock+0x9c/0x140",
>> > +"    [ 2174.334080]  ? irq_work_queue+0x2d/0x50",
>> > +"    [ 2174.338352]  ? __pfx_init_module+0x10/0x10 [rust_panic]",
>> > +"    [ 2174.344183]  <rust_panic::HelloPanic>::step_two+0x20/0xe0 
>> > [rust_panic]",
>> > +"    [ 2174.353698]  ? _printk+0x6b/0x90",
>> > +"    [ 2174.357303]  init_module+0x57/0xff0 [rust_panic]",
>> > +"    [ 2174.362456]  ? __pfx_init_module+0x10/0x10 [rust_panic]",
>> > +"    ...",
>> >
>> >   NULL
>> >   };
>> > diff --git a/kernel.c b/kernel.c
>> > index e4213d7a663e..e077275d7ed6 100644
>> > --- a/kernel.c
>> > +++ b/kernel.c
>> > @@ -5136,7 +5136,7 @@ cmd_log(void)
>> >
>> >       msg_flags = 0;
>> >
>> > -        while ((c = getopt(argcnt, args, "Ttdmasc")) != EOF) {
>> > +        while ((c = getopt(argcnt, args, "TtdmascR")) != EOF) {
>> >                   switch(c)
>> >                   {
>> >               case 'T':
>> > @@ -5160,6 +5160,9 @@ cmd_log(void)
>> >               case 'c':
>> >                       msg_flags |= SHOW_LOG_CALLER;
>> >                       break;
>> > +             case 'R':
>> > +                     msg_flags |= SHOW_LOG_RUST;
>> > +                     break;
>> >                   default:
>> >                           argerrs++;
>> >                           break;
>> > diff --git a/printk.c b/printk.c
>> > index 51b618e2a434..b8fcc8e58160 100644
>> > --- a/printk.c
>> > +++ b/printk.c
>> > @@ -202,7 +202,7 @@ dump_record(struct prb_map *m, unsigned long id, int 
>> > msg_flags)
>> >
>> >       text = m->text_data + begin;
>> >
>> > -     if (text_len > BUFSIZE) {
>> > +     if ((msg_flags & SHOW_LOG_RUST) && (text_len > BUFSIZE)) {
>> >               error(WARNING, "\nThe messages could be truncated!\n");
>> >               text_len = BUFSIZE;
>> >       }
>> > @@ -210,36 +210,41 @@ dump_record(struct prb_map *m, unsigned long id, int 
>> > msg_flags)
>> >       for (i = 0, p = text; i < text_len; i++, p++) {
>> >               if (*p == '\n')
>> >                       fprintf(fp, "\n%s", space(ilen));
>> > -             else if (isprint(*p) || isspace(*p))
>> > +             else if ((msg_flags & SHOW_LOG_RUST) && (isprint(*p) || 
>> > isspace(*p)))
>> >                       sprintf(&buf[i], "%c", *p);
>> > +             else if (isprint(*p) || isspace(*p))
>> > +                     fputc(*p, fp);
>> >               else
>> >                       fputc('.', fp);
>> >       }
>> >       /*
>> >        * Try to demangle a mangled Rust symbol(calltrace) from log buffer
>> >        */
>> > -     char *p1 = strstr(buf, "_R");
>> > -     if (!p1)
>> > -             p1 = strstr(buf, "_ZN");
>> > -     char *p2 = strrchr(buf, '+');
>> > -     if (p1 && p2) {
>> > -             char mangled[BUFSIZE] = {0};
>> > -             char demangled[BUFSIZE] = {0};
>> > -             char *res;
>> > -             size_t slen = p1 - buf;
>> > -
>> > -             if (slen)
>> > -                     memcpy(demangled, buf, slen);
>> > -
>> > -             memcpy(mangled, p1, p2-p1);
>> > -             res = rust_demangle(mangled, DMGL_RUST);
>> > -             if (res) {
>> > -                     snprintf(demangled+slen, BUFSIZE-slen, "%s%s", res, 
>> > p2);
>> > -                     fprintf(fp, "%s",demangled);
>> > -                     free(res);
>> > -             }
>> > -     } else
>> > -             fprintf(fp, "%s", buf);
>> > +     if (msg_flags & SHOW_LOG_RUST) {
>> > +             char *p1 = strstr(buf, "_R");
>> > +             if (!p1)
>> > +                     p1 = strstr(buf, "_ZN");
>> > +             char *p2 = strrchr(buf, '+');
>> > +             if (p1 && p2) {
>> > +                     char mangled[BUFSIZE] = {0};
>> > +                     char demangled[BUFSIZE] = {0};
>> > +                     char *res;
>> > +                     size_t slen = p1 - buf;
>> > +
>> > +                     if (slen)
>> > +                             memcpy(demangled, buf, slen);
>> > +
>> > +                     memcpy(mangled, p1, p2-p1);
>> > +                     res = rust_demangle(mangled, DMGL_RUST);
>> > +                     if (res) {
>> > +                             snprintf(demangled+slen, BUFSIZE-slen, 
>> > "%s%s", res, p2);
>> > +                             fprintf(fp, "%s",demangled);
>> > +                             free(res);
>> > +                     } else
>> > +                             fprintf(fp, "%s", buf);
>> > +             } else
>> > +                     fprintf(fp, "%s", buf);
>> > +     }
>> >
>> >       if (msg_flags & SHOW_LOG_DICT) {
>> >               text = info + OFFSET(printk_info_dev_info) +
--
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