On Thu, Sep 18, 2025 at 9:50 AM HAGIO KAZUHITO(萩尾 一仁) <k-hagio...@nec.com>
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 <k-hagio...@nec.com>
> > Signed-off-by: Lianbo Jiang <liji...@redhat.com>
>
> 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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