Hi, Tao
Thank you for the review.

On Thu, Sep 4, 2025 at 1:08 PM Tao Liu <[email protected]> wrote:

> Hi lianbo,
>
> Just some nits.
>
> On Wed, Aug 27, 2025 at 4:10 PM Lianbo Jiang <[email protected]> wrote:
> >
> > Without the patch:
> >   crash> log
> >   ...
> >   [ 2174.308966] Call Trace:
> >   [ 2174.311693]  <TASK>
> >   [ 2174.314033]  dump_stack_lvl+0x5d/0x80
> >   [ 2174.318125]  panic+0x156/0x32a
> >   [ 2174.321539]  _RNvCscb18lrEyTSA_10rust_panic10area_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]
> _RNvMCscb18lrEyTSA_10rust_panicNtB2_10HelloPanic8step_two+0x20/0xe0
> [rust_panic]
> >   [ 2174.353698]  ? _printk+0x6b/0x90
> >   ...
> >
> > With the patch:
> >   crash> log
> >   ...
> >   [ 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
> >   ...
> >
> > Signed-off-by: Lianbo Jiang <[email protected]>
> > ---
> >  Makefile |  2 +-
> >  printk.c | 28 +++++++++++++++++++++++++++-
> >  2 files changed, 28 insertions(+), 2 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index fc1c9588dcfa..b277129f6df2 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -421,7 +421,7 @@ kernel.o: ${GENERIC_HFILES} kernel.c
> >         ${CC} -c ${CRASH_CFLAGS} kernel.c -I${BFD_DIRECTORY}
> -I${GDB_INCLUDE_DIRECTORY} ${WARNING_OPTIONS} ${WARNING_ERROR}
> >
> >  printk.o: ${GENERIC_HFILES} printk.c
> > -       ${CC} -c ${CRASH_CFLAGS} printk.c ${WARNING_OPTIONS}
> ${WARNING_ERROR}
> > +       ${CC} -c ${CRASH_CFLAGS} printk.c -I${GDB_INCLUDE_DIRECTORY}
> ${WARNING_OPTIONS} ${WARNING_ERROR}
> >
> >  gdb_interface.o: ${GENERIC_HFILES} gdb_interface.c
> >         ${CC} -c ${CRASH_CFLAGS} gdb_interface.c ${WARNING_OPTIONS}
> ${WARNING_ERROR}
> > diff --git a/printk.c b/printk.c
> > index 95db7e607e4c..6a87a790b892 100644
> > --- a/printk.c
> > +++ b/printk.c
> > @@ -1,5 +1,6 @@
> >  #include "defs.h"
> >  #include <ctype.h>
> > +#include "demangle.h"
> >
> >  /* convenience struct for passing many values to helper functions */
> >  struct prb_map {
> > @@ -205,10 +206,35 @@ dump_record(struct prb_map *m, unsigned long id,
> int msg_flags)
> >                 if (*p == '\n')
> >                         fprintf(fp, "\n%s", space(ilen));
> >                 else if (isprint(*p) || isspace(*p))
> > -                       fputc(*p, fp);
> > +                       sprintf(&buf[i], "%c", *p);
> >                 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 = strchrnul(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) {
> > +                       sprintf(demangled+slen, "%s%s", res,p2);
>
> The (de)mangled buf size is 1500. First copied slen chars into
> demangled, then sprintf res and p2 into demangled buf without length
> check.Though this might be a rare case, but I guess a snprintf with a
>

Theoretically yes, but actually I never saw a very long string in the
printk buffer because it would have bad readability.
Anyway, how about the following changes?

diff --git a/printk.c b/printk.c
index 6a87a790b892..c547ea8c3f9f 100644
--- a/printk.c
+++ b/printk.c
@@ -202,6 +202,11 @@ dump_record(struct prb_map *m, unsigned long id, int
msg_flags)

        text = m->text_data + begin;

+       if (text_len > BUFSIZE) {
+               error(WARNING, "\nThe messages could be truncated!\n");
+               text_len = BUFSIZE;
+       }
+
        for (i = 0, p = text; i < text_len; i++, p++) {
                if (*p == '\n')
                        fprintf(fp, "\n%s", space(ilen));
@@ -229,7 +234,7 @@ dump_record(struct prb_map *m, unsigned long id, int
msg_flags)
                memcpy(mangled, p1, p2-p1);
                res = rust_demangle(mangled, DMGL_RUST);
                if (res) {
-                       sprintf(demangled+slen, "%s%s", res,p2);
+                       snprintf(demangled+slen, BUFSIZE, "%s%s", res, p2);
                        fprintf(fp, "%s",demangled);
                        free(res);
                }

Thanks
Lianbo

length check is safer for preventing overflow, since we are within
> ringbuffer buf, I'm not sure how much slen it may be.
>
The rest of the patch are good to me.
>
> Thanks,
> Tao Liu
>
> > +                       fprintf(fp, "%s",demangled);
> > +                       free(res);
> > +               }
> > +       } else
> > +               fprintf(fp, "%s", buf);
> >
> >         if (msg_flags & SHOW_LOG_DICT) {
> >                 text = info + OFFSET(printk_info_dev_info) +
> > --
> > 2.50.1
> > --
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>
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