Le 31/03/2020 à 00:05, Philippe Mathieu-Daudé a écrit : > On 3/30/20 9:07 PM, Brice Goglin wrote: >> When the program name is very long, qemu-user may truncate it in >> /proc/self/stat. However the truncation must keep the ending ") " >> to conform to the proc manpage which says: >> (2) comm %s >> The filename of the executable, in parentheses. This >> is visible whether or not the executable is swapped >> out. >> >> To reproduce: >> $ ln -s /bin/cat <filenamewithmorethan128chars> >> $ qemu-x86_64 ./<filenamewithmorethan128chars> /proc/self/stat >> >> Before the patch, you get: >> 1134631 (<filenametruncated>0 0 0 0 0 0 0 0 ... >> After the patch: >> 1134631 (<filenametruncat>) 0 0 0 0 0 0 0 0 ... >> >> This fixes an issue with hwloc failing to parse /proc/self/stat >> when Ludovic Courtes was testing it in guix over qemu-aarch64. >> >> Signed-off-by: Brice Goglin<brice.gog...@inria.fr> >> >> diff --git a/linux-user/syscall.c b/linux-user/syscall.c >> index 5af55fca78..a1126dcf5b 100644 >> --- a/linux-user/syscall.c >> +++ b/linux-user/syscall.c >> @@ -7305,7 +7305,10 @@ static int open_self_stat(void *cpu_env, int fd) >> snprintf(buf, sizeof(buf), "%"PRId64 " ", val); >> } else if (i == 1) { >> /* app name */ >> - snprintf(buf, sizeof(buf), "(%s) ", ts->bprm->argv[0]); >> + len = snprintf(buf, sizeof(buf), "(%s) ", ts->bprm->argv[0]); >> + if (len >= sizeof(buf)) >> + /* bring back the ending ") " that was truncated */ >> + strcpy(buf+sizeof(buf)-3, ") "); > > Maybe we can avoid the sprintf() call: > > -- >8 -- > diff --git a/linux-user/syscall.c b/linux-user/syscall.c > --- a/linux-user/syscall.c > +++ b/linux-user/syscall.c > @@ -7305,7 +7305,11 @@ static int open_self_stat(void *cpu_env, int fd) > snprintf(buf, sizeof(buf), "%"PRId64 " ", val); > } else if (i == 1) { > /* app name */ > - snprintf(buf, sizeof(buf), "(%s) ", ts->bprm->argv[0]); > + char *ptr = buf; > + > + *ptr++ = '('; > + ptr = stpncpy(ptr, ts->bprm->argv[0], sizeof(buf) - 3); > + strcpy(ptr, ") "); > } else if (i == 27) { > /* stack bottom */ > val = start_stack; >
This works too. Brice