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Subject[PATCH V3 17/17] perf buildid-cache: kcore_copy: Amend the offset of sections that remap kernel text
Date
x86 PTI entry trampolines all map to the same physical page. If that is
reflected in the program headers of /proc/kcore, then do the same for the
copy of kcore.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
---
tools/perf/util/symbol-elf.c | 53 ++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/tools/perf/util/symbol-elf.c b/tools/perf/util/symbol-elf.c
index 584966913aeb..29770ea61768 100644
--- a/tools/perf/util/symbol-elf.c
+++ b/tools/perf/util/symbol-elf.c
@@ -1390,6 +1390,7 @@ struct phdr_data {
u64 addr;
u64 len;
struct list_head node;
+ struct phdr_data *remaps;
};

struct sym_data {
@@ -1597,16 +1598,62 @@ static int kcore_copy__read_maps(struct kcore_copy_info *kci, Elf *elf)
return 0;
}

+static void kcore_copy__find_remaps(struct kcore_copy_info *kci)
+{
+ struct phdr_data *p, *k = NULL;
+ u64 kend;
+
+ if (!kci->stext)
+ return;
+
+ /* Find phdr that corresponds to the kernel map (contains stext) */
+ kcore_copy__for_each_phdr(kci, p) {
+ u64 pend = p->addr + p->len - 1;
+
+ if (p->addr <= kci->stext && pend >= kci->stext) {
+ k = p;
+ break;
+ }
+ }
+
+ if (!k)
+ return;
+
+ kend = k->offset + k->len;
+
+ /* Find phdrs that remap the kernel */
+ kcore_copy__for_each_phdr(kci, p) {
+ u64 pend = p->offset + p->len;
+
+ if (p == k)
+ continue;
+
+ if (p->offset >= k->offset && pend <= kend)
+ p->remaps = k;
+ }
+}
+
static void kcore_copy__layout(struct kcore_copy_info *kci)
{
struct phdr_data *p;
off_t rel = 0;

+ kcore_copy__find_remaps(kci);
+
kcore_copy__for_each_phdr(kci, p) {
- p->rel = rel;
- rel += p->len;
+ if (!p->remaps) {
+ p->rel = rel;
+ rel += p->len;
+ }
kci->phnum += 1;
}
+
+ kcore_copy__for_each_phdr(kci, p) {
+ struct phdr_data *k = p->remaps;
+
+ if (k)
+ p->rel = p->offset - k->offset + k->rel;
+ }
}

static int kcore_copy__calc_maps(struct kcore_copy_info *kci, const char *dir,
@@ -1821,6 +1868,8 @@ int kcore_copy(const char *from_dir, const char *to_dir)
kcore_copy__for_each_phdr(&kci, p) {
off_t offs = p->rel + offset;

+ if (p->remaps)
+ continue;
if (copy_bytes(kcore.fd, p->offset, extract.fd, offs, p->len))
goto out_extract_close;
}
--
1.9.1
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