Re: [PATCH] perf tools: Fix arm64 build error with gcc-11
From: Leo Yan <hidden>
Date: 2021-02-09 12:18:35
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Hi Jianlin, On Tue, Feb 09, 2021 at 07:33:57PM +0800, Jianlin Lv wrote:
quoted hunk ↗ jump to hunk
gcc version: 11.0.0 20210208 (experimental) (GCC) Following build error on arm64: ....... In function ‘printf’, inlined from ‘regs_dump__printf’ at util/session.c:1141:3, inlined from ‘regs__printf’ at util/session.c:1169:2: /usr/include/aarch64-linux-gnu/bits/stdio2.h:107:10: \ error: ‘%-5s’ directive argument is null [-Werror=format-overflow=] 107 | return __printf_chk (__USE_FORTIFY_LEVEL - 1, __fmt, \ __va_arg_pack ()); ...... In function ‘fprintf’, inlined from ‘perf_sample__fprintf_regs.isra’ at \ builtin-script.c:622:14: /usr/include/aarch64-linux-gnu/bits/stdio2.h:100:10: \ error: ‘%5s’ directive argument is null [-Werror=format-overflow=] 100 | return __fprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1, __fmt, 101 | __va_arg_pack ()); cc1: all warnings being treated as errors ....... This patch fixes Wformat-overflow warnings by replacing the return value NULL of perf_reg_name with "unknown". Signed-off-by: Jianlin Lv <redacted> --- tools/perf/arch/arm64/include/perf_regs.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)diff --git a/tools/perf/arch/arm64/include/perf_regs.h b/tools/perf/arch/arm64/include/perf_regs.h index baaa5e64a3fb..901419f907c0 100644 --- a/tools/perf/arch/arm64/include/perf_regs.h +++ b/tools/perf/arch/arm64/include/perf_regs.h@@ -85,10 +85,10 @@ static inline const char *perf_reg_name(int id) case PERF_REG_ARM64_PC: return "pc"; default: - return NULL; + return "unknown"; } - return NULL; + return "unknown";
This issue is a common issue crossing all archs. So it's better to change the code in the places where calls perf_reg_name(), e.g. in util/session.c:
--- a/tools/perf/util/session.c
+++ b/tools/perf/util/session.c@@ -1135,12 +1135,14 @@ static void branch_stack__printf(struct perf_sample *sample, bool callstack) static void regs_dump__printf(u64 mask, u64 *regs) { unsigned rid, i = 0; + char *reg_name; for_each_set_bit(rid, (unsigned long *) &mask, sizeof(mask) * 8) { u64 val = regs[i++]; + reg_name = perf_reg_name(rid); printf(".... %-5s 0x%016" PRIx64 "\n", - perf_reg_name(rid), val); + reg_name ?: "Unknown", val); } }
And another potential issue is the format specifier "%-5s", it prints out maximum to 5 chars, but actually string "Unknown" has 7 chars. Actually the format specifier breaks other archs register names, e.g. [1][2], seems to me, it's better to change as "%-8s", you might need to use a dedicated patch for format specifier changes. Thanks, Leo [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/arch/powerpc/include/perf_regs.h#n57 [2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/perf/arch/csky/include/perf_regs.h#n83 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel