On = 18-Jan-2021, at 3:51 PM, kajoljain <kjain@linux.ibm.com> = wrote:

On 1/12/21 3:08 PM, Jiri Olsa = wrote:
On Mon, Dec 28, 2020 at 09:14:14PM = -0500, Athira Rajeev wrote:

SNIP

c000000002799370 b backtrace_flag
c000000002799378 B = radix_tree_node_cachep
c000000002799380 B = __bss_stop
c0000000027a0000 B _end
c008000003890000 t = icmp_checkentry =      [ip_tables]
c008000003890038 t = ipt_alloc_initial_table =      [ip_tables]
c008000003890468 T = ipt_do_table [ip_tables]
c008000003890de8 T = ipt_unregister_table_pre_exit =        [ip_tables]
...

Perf = calls function symbols__fixup_end() which sets the end of symbol
to = 0xc008000003890000, which is the next address and this is the = start
address of first module (icmp_checkentry in above) which will = make the
huge symbol size of 0x80000010f0000.

After = symbols__fixup_end:
symbols__fixup_end: sym->name: _end, = sym->start: 0xc0000000027a0000,
sym->end: = 0xc008000003890000

On powerpc, kernel text segment is located at = 0xc000000000000000
whereas the modules are located at very high = memory addresses,
0xc00800000xxxxxxx. Since the gap between end of = kernel text segment
and beginning of first module's address is high, = histogram allocation
using calloc fails.

Fix this by detecting = the kernel's last symbol and limiting
the range of last kernel symbol = to pagesize.

Patch looks good to = me.

Tested-By: Kajol = Jain<kjain@linux.ibm.com>

Thanks,
Kajol = Jain

Signed-off-by: Athira = Rajeev<atrajeev@linux.vnet.ibm.com>

I can't = test, but since the same approach works for arm and s390,
this also = looks ok

Acked-by: Jiri Olsa = <jolsa@redhat.com>

thanks,
jirka

Hi Arnaldo,

Can you please help review this patch and = merge if this looks good..

Thanks
Athira

---
tools/perf/arch/powerpc/util/Build =     | 1 = +
tools/perf/arch/powerpc/util/machine.c | 24 = ++++++++++++++++++++++++
2 files changed, 25 insertions(+)
create = mode 100644 tools/perf/arch/powerpc/util/machine.c

diff --git = a/tools/perf/arch/powerpc/util/Build = b/tools/perf/arch/powerpc/util/Build
index e86e210bf514..b7945e5a543b = 100644
--- a/tools/perf/arch/powerpc/util/Build
+++ = b/tools/perf/arch/powerpc/util/Build
@@ -1,4 +1,5 @@
perf-y +=3D = header.o
+perf-y +=3D machine.o
perf-y +=3D kvm-stat.o
perf-y = +=3D perf_regs.o
perf-y +=3D mem-events.o
diff --git = a/tools/perf/arch/powerpc/util/machine.c = b/tools/perf/arch/powerpc/util/machine.c
new file mode = 100644
index 000000000000..c30e5cc88c16
--- /dev/null
+++ = b/tools/perf/arch/powerpc/util/machine.c
@@ -0,0 +1,24 @@
+// = SPDX-License-Identifier: GPL-2.0
+
+#include = <stdio.h>
+#include <string.h>
+#include = <internal/lib.h> // page_size
+#include "debug.h"
+#include = "symbol.h"
+
+/* On powerpc kernel text segment start at memory = addresses, 0xc000000000000000
+ * whereas the modules are located at = very high memory addresses,
+ * for example 0xc00800000xxxxxxx. The = gap between end of kernel text segment
+ * and beginning of first = module's text segment is very high.
+ * Therefore do not fill this = gap and do not assign it to the kernel dso map.
+ */
+
+void = arch__symbols__fixup_end(struct symbol *p, struct symbol = *c)
+{
+ = if (strchr(p->name, '[') =3D=3D NULL && = strchr(c->name, '['))
+ /* Limit the range of last kernel = symbol */
+ = = p->end +=3D page_size;
+ else
+ p->end = =3D c->start;
+ pr_debug4("%s sym:%s end:%#lx\n", = __func__, p->name, p->end);
+}
-- =
1.8.3.1