From: Tianchen Ding Date: Mon, 1 Jun 2026 02:32:51 +0000 (+0800) Subject: selftests/ftrace: Fix trace_marker_raw test on 64K page kernels X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=65f26d15f7db80b0a3f995c518cdddb50e6dea99;p=thirdparty%2Fkernel%2Flinux.git selftests/ftrace: Fix trace_marker_raw test on 64K page kernels On ARM64 kernels with 64K pages, the trace_marker_raw test fails because bash's printf builtin uses stdio buffering which splits output into multiple small write() calls to the tracefs file. Since each individual write is within TRACE_MARKER_MAX_SIZE (4096), they all succeed, causing the "too big" write test to incorrectly pass. Fix by writing through dd with iflag=fullblock to guarantee a single atomic write() syscall to trace_marker_raw. Link: https://lore.kernel.org/r/20260601023251.1916483-1-dtcccc@linux.alibaba.com Fixes: 37f46601383a ("selftests/tracing: Add basic test for trace_marker_raw file") Signed-off-by: Tianchen Ding Reviewed-by: Steven Rostedt Signed-off-by: Shuah Khan --- diff --git a/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc b/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc index 8e905d4fe6dd..f985ff391463 100644 --- a/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc +++ b/tools/testing/selftests/ftrace/test.d/00basic/trace_marker_raw.tc @@ -36,15 +36,23 @@ make_str() { data=`printf -- 'X%.0s' $(seq $cnt)` - printf "${val}${data}" + # Return escape-sequence text (e.g. "\003\000..."); the caller + # converts to binary. Shell command substitution strips NUL bytes, + # so the binary form cannot survive being captured into a variable. + printf '%s' "${val}${data}" } write_buffer() { id=$1 size=$2 - # write the string into the raw marker - make_str $id $size > trace_marker_raw + str=`make_str $id $size` + len=`printf "$str" | wc -c` + # Pipe through dd to ensure a single atomic write() syscall + # on architectures with 64K pages, where shell's printf builtin + # uses stdio buffering which may split the output into multiple + # writes. + printf "$str" | dd of=trace_marker_raw bs=$len iflag=fullblock }