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perf annotate: Fix s390 gap between kernel end and module start

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During execution of command 'perf top' the error message:

   Not enough memory for annotating '__irf_end' symbol!)

is emitted from this call sequence:
  __cmd_top
    perf_top__mmap_read
      perf_top__mmap_read_idx
        perf_event__process_sample
          hist_entry_iter__add
            hist_iter__top_callback
              perf_top__record_precise_ip
                hist_entry__inc_addr_samples
                  symbol__inc_addr_samples
                    symbol__get_annotation
                      symbol__alloc_hist

In this function the size of symbol __irf_end is calculated. The size of
a symbol is the difference between its start and end address.

When the symbol was read the first time, its start and end was set to:

   symbol__new: __irf_end 0xe954d0-0xe954d0

which is correct and maps with /proc/kallsyms:

   root@s8360046:~/linux-4.15.0/tools/perf# fgrep _irf_end /proc/kallsyms
   0000000000e954d0 t __irf_end
   root@s8360046:~/linux-4.15.0/tools/perf#

In function symbol__alloc_hist() the end of symbol __irf_end is

  symbol__alloc_hist sym:__irf_end start:0xe954d0 end:0x3ff80045a8

which is identical with the first module entry in /proc/kallsyms

This results in a symbol size of __irf_req for histogram analyses of
70334140059072 bytes and a malloc() for this requested size fails.

The root cause of this is function
  __dso__load_kallsyms()
  +-> symbols__fixup_end()

Function symbols__fixup_end() enlarges the last symbol in the kallsyms
map:

   # fgrep __irf_end /proc/kallsyms
   0000000000e954d0 t __irf_end
   #

to the start address of the first module:
   # cat /proc/kallsyms | sort  | egrep ' [tT] '
   ....
   0000000000e952d0 T __security_initcall_end
   0000000000e954d0 T __initramfs_size
   0000000000e954d0 t __irf_end
   000003ff800045a8 T fc_get_event_number       [scsi_transport_fc]
   000003ff800045d0 t store_fc_vport_disable    [scsi_transport_fc]
   000003ff800046a8 T scsi_is_fc_rport  [scsi_transport_fc]
   000003ff800046d0 t fc_target_setup   [scsi_transport_fc]

On s390 the kernel is located around memory address 0x200, 0x10000 or
0x100000, depending on linux version. Modules however start some- where
around 0x3ff xxxx xxxx.

This is different than x86 and produces a large gap for which histogram
allocation fails.

Fix this by detecting the kernel's last symbol and do no adjustment for
it. Introduce a weak function and handle s390 specifics.

Reported-by: Klaus Theurich <klaus.theurich@de.ibm.com>
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Hendrik Brueckner <brueckner@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: stable@vger.kernel.org
Link: http://lkml.kernel.org/r/20190724122703.3996-2-tmricht@linux.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Thomas Richter 2019-07-24 14:27:03 +02:00 committed by Arnaldo Carvalho de Melo
parent 12a6d2940b
commit b9c0a64901
3 changed files with 24 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
tools/perf/arch/s390/util/machine.c
View File

@ -6,6 +6,7 @@
#include "machine.h"
#include "api/fs/fs.h"
#include "debug.h"
#include "symbol.h"
int arch__fix_module_text_start(u64 *start, u64 *size, const char *name)
{
@ -33,3 +34,19 @@ int arch__fix_module_text_start(u64 *start, u64 *size, const char *name)
return 0;
}
/* On s390 kernel text segment start is located at very low memory addresses,
* for example 0x10000. Modules are located at very high memory addresses,
* for example 0x3ff xxxx xxxx. The gap between end of kernel text segment
* and beginning of first module's text segment is very big.
* 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, '[') == NULL && strchr(c->name, '['))
/* Last kernel symbol mapped to end of page */
p->end = roundup(p->end, page_size);
else
p->end = c->start;
pr_debug4("%s sym:%s end:%#lx\n", __func__, p->name, p->end);
}

7
tools/perf/util/symbol.c
View File

@ -92,6 +92,11 @@ static int prefix_underscores_count(const char *str)
return tail - str;
}
void __weak arch__symbols__fixup_end(struct symbol *p, struct symbol *c)
{
p->end = c->start;
}
const char * __weak arch__normalize_symbol_name(const char *name)
{
return name;
@ -218,7 +223,7 @@ void symbols__fixup_end(struct rb_root_cached *symbols)
curr = rb_entry(nd, struct symbol, rb_node);
if (prev->end == prev->start && prev->end != curr->start)
prev->end = curr->start;
arch__symbols__fixup_end(prev, curr);
}
/* Last entry */

1
tools/perf/util/symbol.h
View File

@ -288,6 +288,7 @@ const char *arch__normalize_symbol_name(const char *name);
#define SYMBOL_A 0
#define SYMBOL_B 1
void arch__symbols__fixup_end(struct symbol *p, struct symbol *c);
int arch__compare_symbol_names(const char *namea, const char *nameb);
int arch__compare_symbol_names_n(const char *namea, const char *nameb,
unsigned int n);