From: Michael Petlan mpetlan@redhat.com
commit 3cf6a32f3f2a45944dd5be5c6ac4deb46bcd3bee upstream.
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.
Fixes: 3b01a413c196c910 ("perf symbols: Improve kallsyms symbol end addr calculation") Signed-off-by: Michael Petlan mpetlan@redhat.com Cc: Athira Jajeev atrajeev@linux.vnet.ibm.com Cc: Jiri Olsa jolsa@kernel.org Cc: Kajol Jain kjain@linux.ibm.com Cc: Madhavan Srinivasan maddy@linux.ibm.com Link: http://lore.kernel.org/lkml/20220317135536.805-1-mpetlan@redhat.com Signed-off-by: Arnaldo Carvalho de Melo acme@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/perf/util/symbol.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -231,7 +231,7 @@ void symbols__fixup_end(struct rb_root_c prev = curr; curr = rb_entry(nd, struct symbol, rb_node);
- if (prev->end == prev->start && prev->end != curr->start) + if (prev->end == prev->start || prev->end != curr->start) arch__symbols__fixup_end(prev, curr); }