Please ignore this patch, I will post v2 later with a slight change.
Sorry about that.
Thanks
Lianbo
On Wed, Sep 17, 2025 at 6:00 PM Lianbo Jiang <liji...@redhat.com> 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>
> ---
> defs.h | 1 +
> help.c | 24 +++++++++++++++++++++++-
> kernel.c | 5 ++++-
> printk.c | 46 +++++++++++++++++++++++++---------------------
> 4 files changed, 53 insertions(+), 23 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..e4cc6dc30065 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;
> }
> @@ -218,26 +218,30 @@ dump_record(struct prb_map *m, unsigned long id, int
> msg_flags)
> /*
> * 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);
> - }
> + 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);
> } else
> fprintf(fp, "%s", buf);
>
> --
> 2.50.1
>
>
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