Before this patch, the symbol end address fixup to be called, needed two conditions being met: if (prev->end == prev->start && prev->end != curr->start) Where "prev->end == prev->start" means that prev is zero-long (and thus needs a fixup) and "prev->end != curr->start" means that fixup hasn't been applied yet However, this logic is incorrect in the following situation: *curr = {rb_node = {__rb_parent_color = 278218928, rb_right = 0x0, rb_left = 0x0}, start = 0xc000000000062354, end = 0xc000000000062354, namelen = 40, type = 2 '\002', binding = 0 '\000', idle = 0 '\000', ignore = 0 '\000', inlined = 0 '\000', arch_sym = 0 '\000', annotate2 = false, name = 0x1159739e "kprobe_optinsn_page\t[__builtin__kprobes]"} *prev = {rb_node = {__rb_parent_color = 278219041, rb_right = 0x109548b0, rb_left = 0x109547c0}, start = 0xc000000000062354, end = 0xc000000000062354, namelen = 12, type = 2 '\002', binding = 1 '\001', idle = 0 '\000', ignore = 0 '\000', inlined = 0 '\000', arch_sym = 0 '\000', annotate2 = false, name = 0x1095486e "optinsn_slot"} In this case, prev->start == prev->end == curr->start == curr->end, thus the condition above thinks that "we need a fixup due to zero length of prev symbol, but it has been probably done, since the prev->end == curr->start", which is wrong. After the patch, the execution path proceeds to arch__symbols__fixup_end function which fixes up the size of prev symbol by adding page_size to its end offset.
Unified · Split
| @@ -231,7 +231,7 @@ void symbols__fixup_end(struct rb_root_cached *symbols) · 230 unmodified lines | |||
| 231 | prev = curr; | 231 | prev = curr; |
| 232 | curr = rb_entry(nd, struct symbol, rb_node); | 232 | curr = rb_entry(nd, struct symbol, rb_node); |
| 233 | 233 | ||
| 234 | if (prev->end == prev->start && prev->end != curr->start) | 234 | if (prev->end == prev->start || prev->end != curr->start) |
| 235 | arch__symbols__fixup_end(prev, curr); | 235 | arch__symbols__fixup_end(prev, curr); |
| 236 | } | 236 | } |
| 237 | 237 | ||