Re: [PATCH 2/5] perf genelf: Use unaligned-safe accessors for debug entries

From: Arnaldo Carvalho de Melo <redacted>

debug_entry records are packed with a variable-length name[] field, so
entries after the first may start at addresses that are not naturally
aligned.  jit_process_debug_info(), get_special_opcode() and
emit_lineno_info() read and write the u64 addr and int lineno fields
through struct member access, which is undefined behavior on
strict-alignment architectures.

Use get_unaligned()/put_unaligned() to read and update each field,
matching the layout the jitdump writers (LLVM, JVM agents) emit, which
packs entries without padding.

struct debug_entry.lineno is signed and emit_advance_lineno() takes a
long line delta that relies on sign extension, so the field is read
into an int: reading it into an unsigned int would turn a backward
line jump into a huge forward one and corrupt the line number program.

Reported-by: sashiko-bot <sashiko-bot@kernel.org>
Cc: Stephane Eranian <redacted>
Assisted-by: LLM
Signed-off-by: Arnaldo Carvalho de Melo <redacted>

Sashiko has reviewed this patch and found no issues. It looks great!

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Sashiko AI review · https://sashiko.dev/#/patchset/20260904144058.3341-1-acme@kernel.org?part=2