| Message ID | 20220301165737.672007-1-ytcoode@gmail.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next] libbpf: Add a check to ensure that page_cnt is non-zero | expand |
| Context | Check | Description |
|---|---|---|
| bpf/vmtest-bpf-next-PR | success | PR summary |
| netdev/tree_selection | success | Clearly marked for bpf-next |
| netdev/fixes_present | success | Fixes tag not required for -next series |
| netdev/subject_prefix | success | Link |
| netdev/cover_letter | success | Single patches do not need cover letters |
| netdev/patch_count | success | Link |
| netdev/header_inline | success | No static functions without inline keyword in header files |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/cc_maintainers | success | CCed 10 of 10 maintainers |
| netdev/build_clang | success | Errors and warnings before: 0 this patch: 0 |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Signed-off-by tag matches author and committer |
| netdev/verify_fixes | success | No Fixes tag |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 23 lines checked |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/source_inline | success | Was 0 now: 0 |
| bpf/vmtest-bpf-next | success | VM_Test |
On Tue, Mar 1, 2022 at 8:57 AM Yuntao Wang <ytcoode@gmail.com> wrote: > > The page_cnt parameter is used to specify the number of memory pages > allocated for each per-CPU buffer, it must be non-zero and a power of 2. > > Currently, the __perf_buffer__new() function attempts to validate that > the page_cnt is a power of 2 but forgets checking for the case where > page_cnt is zero, we can fix it by replacing 'page_cnt & (page_cnt - 1)' > with '!is_power_of_2(page_cnt)'. > > Thus we also don't need to add a check in perf_buffer__new_v0_6_0() to > make sure that page_cnt is non-zero and the check for zero in > perf_buffer__new_raw_v0_6_0() can also be removed. > > The code is cleaner and more readable. > > Signed-off-by: Yuntao Wang <ytcoode@gmail.com> > --- > tools/lib/bpf/libbpf.c | 5 +++-- > 1 file changed, 3 insertions(+), 2 deletions(-) > > diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c > index be6480e260c4..4dd1d82cd5b9 100644 > --- a/tools/lib/bpf/libbpf.c > +++ b/tools/lib/bpf/libbpf.c > @@ -33,6 +33,7 @@ > #include <linux/filter.h> > #include <linux/list.h> > #include <linux/limits.h> > +#include <linux/log2.h> we don't have this header implemented in Github repo, so this will be unnecessary painful > #include <linux/perf_event.h> > #include <linux/ring_buffer.h> > #include <linux/version.h> > @@ -10951,7 +10952,7 @@ struct perf_buffer *perf_buffer__new_raw_v0_6_0(int map_fd, size_t page_cnt, > { > struct perf_buffer_params p = {}; > > - if (page_cnt == 0 || !attr) > + if (!attr) > return libbpf_err_ptr(-EINVAL); > > if (!OPTS_VALID(opts, perf_buffer_raw_opts)) > @@ -10992,7 +10993,7 @@ static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt, > __u32 map_info_len; > int err, i, j, n; > > - if (page_cnt & (page_cnt - 1)) { > + if (!is_power_of_2(page_cnt)) { so let's instead just use `page_cnt == 0 || (page_cnt & (page_cnt - 1))` here explicitly > pr_warn("page count should be power of two, but is %zu\n", > page_cnt); > return ERR_PTR(-EINVAL); > -- > 2.35.1 >
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c index be6480e260c4..4dd1d82cd5b9 100644 --- a/tools/lib/bpf/libbpf.c +++ b/tools/lib/bpf/libbpf.c @@ -33,6 +33,7 @@ #include <linux/filter.h> #include <linux/list.h> #include <linux/limits.h> +#include <linux/log2.h> #include <linux/perf_event.h> #include <linux/ring_buffer.h> #include <linux/version.h> @@ -10951,7 +10952,7 @@ struct perf_buffer *perf_buffer__new_raw_v0_6_0(int map_fd, size_t page_cnt, { struct perf_buffer_params p = {}; - if (page_cnt == 0 || !attr) + if (!attr) return libbpf_err_ptr(-EINVAL); if (!OPTS_VALID(opts, perf_buffer_raw_opts)) @@ -10992,7 +10993,7 @@ static struct perf_buffer *__perf_buffer__new(int map_fd, size_t page_cnt, __u32 map_info_len; int err, i, j, n; - if (page_cnt & (page_cnt - 1)) { + if (!is_power_of_2(page_cnt)) { pr_warn("page count should be power of two, but is %zu\n", page_cnt); return ERR_PTR(-EINVAL);
The page_cnt parameter is used to specify the number of memory pages allocated for each per-CPU buffer, it must be non-zero and a power of 2. Currently, the __perf_buffer__new() function attempts to validate that the page_cnt is a power of 2 but forgets checking for the case where page_cnt is zero, we can fix it by replacing 'page_cnt & (page_cnt - 1)' with '!is_power_of_2(page_cnt)'. Thus we also don't need to add a check in perf_buffer__new_v0_6_0() to make sure that page_cnt is non-zero and the check for zero in perf_buffer__new_raw_v0_6_0() can also be removed. The code is cleaner and more readable. Signed-off-by: Yuntao Wang <ytcoode@gmail.com> --- tools/lib/bpf/libbpf.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)