[tip:perf/core] perf kcore_copy: Amend the offset of sections that remap kernel text

tip-bot for Adrian Hunter
2018-05-24T05:45:48Z

Commit-ID: 22916fdb9c50e8fb303bdcedca88fd8798a85844
Gitweb: https://git.kernel.org/tip/22916fdb9c50e8fb303bdcedca88fd8798a85844
Author: Adrian Hunter <adrian.hunter@intel.com>
AuthorDate: Tue, 22 May 2018 13:54:45 +0300
Committer: Arnaldo Carvalho de Melo <acme@redhat.com>
CommitDate: Wed, 23 May 2018 10:26:44 -0300

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>
---
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;
}