| From 3cf6a32f3f2a45944dd5be5c6ac4deb46bcd3bee Mon Sep 17 00:00:00 2001 |
| From: Michael Petlan <mpetlan@redhat.com> |
| Date: Thu, 17 Mar 2022 14:55:36 +0100 |
| Subject: perf symbols: Fix symbol size calculation condition |
| |
| 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); |
| } |
| |