Message ID | 20210426192949.416837-4-andrii@kernel.org (mailing list archive) |
---|---|
State | Accepted |
Delegated to: | BPF |
Headers | show |
Series | CO-RE relocation selftests fixes | expand |
Context | Check | Description |
---|---|---|
netdev/cover_letter | success | Link |
netdev/fixes_present | success | Link |
netdev/patch_count | success | Link |
netdev/tree_selection | success | Clearly marked for bpf-next |
netdev/subject_prefix | success | Link |
netdev/cc_maintainers | warning | 9 maintainers not CCed: yhs@fb.com kpsingh@kernel.org kafai@fb.com clang-built-linux@googlegroups.com ast@kernel.org nathan@kernel.org john.fastabend@gmail.com songliubraving@fb.com ndesaulniers@google.com |
netdev/source_inline | success | Was 0 now: 0 |
netdev/verify_signedoff | success | Link |
netdev/module_param | success | Was 0 now: 0 |
netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
netdev/verify_fixes | success | Link |
netdev/checkpatch | fail | ERROR: trailing statements should be on next line WARNING: Avoid unnecessary line continuations |
netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
netdev/header_inline | success | Link |
diff --git a/tools/lib/bpf/bpf_core_read.h b/tools/lib/bpf/bpf_core_read.h index 53b3e199fb25..09ebe3db5f2f 100644 --- a/tools/lib/bpf/bpf_core_read.h +++ b/tools/lib/bpf/bpf_core_read.h @@ -88,11 +88,19 @@ enum bpf_enum_value_kind { const void *p = (const void *)s + __CORE_RELO(s, field, BYTE_OFFSET); \ unsigned long long val; \ \ + /* This is a so-called barrier_var() operation that makes specified \ + * variable "a black box" for optimizing compiler. \ + * It forces compiler to perform BYTE_OFFSET relocation on p and use \ + * its calculated value in the switch below, instead of applying \ + * the same relocation 4 times for each individual memory load. \ + */ \ + asm volatile("" : "=r"(p) : "0"(p)); \ + \ switch (__CORE_RELO(s, field, BYTE_SIZE)) { \ - case 1: val = *(const unsigned char *)p; \ - case 2: val = *(const unsigned short *)p; \ - case 4: val = *(const unsigned int *)p; \ - case 8: val = *(const unsigned long long *)p; \ + case 1: val = *(const unsigned char *)p; break; \ + case 2: val = *(const unsigned short *)p; break; \ + case 4: val = *(const unsigned int *)p; break; \ + case 8: val = *(const unsigned long long *)p; break; \ } \ val <<= __CORE_RELO(s, field, LSHIFT_U64); \ if (__CORE_RELO(s, field, SIGNED)) \