perf kcore_copy: Amend the offset of sections that remap kernel text

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>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/1526986485-6562-18-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files 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;
         }