Revision d0313e629f2690edfd269896b398048275227db0 authored by Ian Rogers on 12 August 2022, 23:09:49 UTC, committed by Arnaldo Carvalho de Melo on 13 August 2022, 18:03:09 UTC
If a shorter string ends a longer string then the shorter string may reuse the longer string at an offset. For example, on x86 the event arith.cycles_div_busy and cycles_div_busy can be folded, even though they have difference names the strings are identical after 6 characters. cycles_div_busy can reuse the arith.cycles_div_busy string at an offset of 6. In pmu-events.c this looks like the following where the 'also:' lists folded strings: /* offset=177541 */ "arith.cycles_div_busy\000\000pipeline\000Cycles the divider is busy\000\000\000event=0x14,period=2000000,umask=0x1\000\000\000\000\000\000\000\000\000" /* also: cycles_div_busy\000\000pipeline\000Cycles the divider is busy\000\000\000event=0x14,period=2000000,umask=0x1\000\000\000\000\000\000\000\000\000 */ As jevents.py combines multiple strings for an event into a larger string, the amount of folding is minimal as all parts of the event must align. Other organizations can benefit more from folding, but lose space by say recording more offsets. Signed-off-by: Ian Rogers <irogers@google.com> Cc: Adrian Hunter <adrian.hunter@intel.com> Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: James Clark <james.clark@arm.com> Cc: Jiri Olsa <jolsa@kernel.org> Cc: John Garry <john.garry@huawei.com> Cc: Kan Liang <kan.liang@linux.intel.com> Cc: Leo Yan <leo.yan@linaro.org> Cc: Mark Rutland <mark.rutland@arm.com> Cc: Mike Leach <mike.leach@linaro.org> Cc: Namhyung Kim <namhyung@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ravi Bangoria <ravi.bangoria@amd.com> Cc: Stephane Eranian <eranian@google.com> Cc: Will Deacon <will@kernel.org> Cc: Xing Zhengjun <zhengjun.xing@linux.intel.com> Cc: linux-arm-kernel@lists.infradead.org Link: https://lore.kernel.org/r/20220812230949.683239-15-irogers@google.com Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
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kallsyms_internal.h
/* SPDX-License-Identifier: GPL-2.0-only */
#ifndef LINUX_KALLSYMS_INTERNAL_H_
#define LINUX_KALLSYMS_INTERNAL_H_
#include <linux/types.h>
/*
* These will be re-linked against their real values
* during the second link stage.
*/
extern const unsigned long kallsyms_addresses[] __weak;
extern const int kallsyms_offsets[] __weak;
extern const u8 kallsyms_names[] __weak;
/*
* Tell the compiler that the count isn't in the small data section if the arch
* has one (eg: FRV).
*/
extern const unsigned int kallsyms_num_syms
__section(".rodata") __attribute__((weak));
extern const unsigned long kallsyms_relative_base
__section(".rodata") __attribute__((weak));
extern const char kallsyms_token_table[] __weak;
extern const u16 kallsyms_token_index[] __weak;
extern const unsigned int kallsyms_markers[] __weak;
#endif // LINUX_KALLSYMS_INTERNAL_H_
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