| Message ID | 1573123866-348262-1-git-send-email-vincent.donnefort@arm.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [1/2] trace-cmd: Enable kptr_restrict | expand |
Hi Vincent! On Thu, 7 Nov 2019 10:51:05 +0000 vincent.donnefort@arm.com wrote: > From: Vincent Donnefort <vincent.donnefort@arm.com> > > kptr_restrict might prevent trace-cmd from accessing /proc/kallsyms, > leading to a trace without the kernel function names resolved. > > Signed-off-by: Vincent Donnefort <vincent.donnefort@arm.com> > > diff --git a/lib/trace-cmd/trace-output.c b/lib/trace-cmd/trace-output.c > index 41932ee..3c4f306 100644 > --- a/lib/trace-cmd/trace-output.c > +++ b/lib/trace-cmd/trace-output.c > @@ -674,6 +674,39 @@ static int read_event_files(struct tracecmd_output *handle, > return ret; > } > > +static void set_proc_kptr_restrict(int reset) > +{ > + char *path = "/proc/sys/kernel/kptr_restrict"; I believe this is a relatively new file. We should do a stat to see if it exists, and if it does not, simply fail silently. I don't think we want to give a warning if the file doesn't exist because the kernel doesn't have it. > + static char saved = 'X'; > + int fd, ret = -1; > + char buf; > + > + fd = open(path, O_RDONLY); > + if (fd < 0) > + goto err; > + > + if (reset) { > + buf = saved; > + } else { > + if (read(fd, &buf, 1) < 0) > + goto err; > + saved = buf; > + buf = '0'; > + } > + close(fd); > + Perhaps if reset is true and buf == 'X', we should simply exit, as it would appear that we never put anything into buf. And probably should make the 'X' a macro: #define KPTR_UNINITIALIZED 'X' static char saved = KPTR_UNINITIALIZED; [..] if (reset && buf == KPTR_UNINITIALIZED) return; -- Steve > + fd = open(path, O_WRONLY); > + if (fd < 0) > + goto err; > + if (write(fd, &buf, 1) > 0) > + ret = 0; > +err: > + if (fd > 0) > + close(fd); > + if (ret) > + warning("can't set kptr_restrict"); > +} > + > static int read_proc_kallsyms(struct tracecmd_output *handle, > const char *kallsyms) > { > @@ -698,12 +731,16 @@ static int read_proc_kallsyms(struct tracecmd_output *handle, > endian4 = convert_endian_4(handle, size); > if (do_write_check(handle, &endian4, 4)) > return -1; > + > + set_proc_kptr_restrict(0); > check_size = copy_file(handle, path); > if (size != check_size) { > errno = EINVAL; > warning("error in size of file '%s'", path); > + set_proc_kptr_restrict(1); > return -1; > } > + set_proc_kptr_restrict(1); > > return 0; > }
diff --git a/lib/trace-cmd/trace-output.c b/lib/trace-cmd/trace-output.c index 41932ee..3c4f306 100644 --- a/lib/trace-cmd/trace-output.c +++ b/lib/trace-cmd/trace-output.c @@ -674,6 +674,39 @@ static int read_event_files(struct tracecmd_output *handle, return ret; } +static void set_proc_kptr_restrict(int reset) +{ + char *path = "/proc/sys/kernel/kptr_restrict"; + static char saved = 'X'; + int fd, ret = -1; + char buf; + + fd = open(path, O_RDONLY); + if (fd < 0) + goto err; + + if (reset) { + buf = saved; + } else { + if (read(fd, &buf, 1) < 0) + goto err; + saved = buf; + buf = '0'; + } + close(fd); + + fd = open(path, O_WRONLY); + if (fd < 0) + goto err; + if (write(fd, &buf, 1) > 0) + ret = 0; +err: + if (fd > 0) + close(fd); + if (ret) + warning("can't set kptr_restrict"); +} + static int read_proc_kallsyms(struct tracecmd_output *handle, const char *kallsyms) { @@ -698,12 +731,16 @@ static int read_proc_kallsyms(struct tracecmd_output *handle, endian4 = convert_endian_4(handle, size); if (do_write_check(handle, &endian4, 4)) return -1; + + set_proc_kptr_restrict(0); check_size = copy_file(handle, path); if (size != check_size) { errno = EINVAL; warning("error in size of file '%s'", path); + set_proc_kptr_restrict(1); return -1; } + set_proc_kptr_restrict(1); return 0; }