linux-kernel - [PATCH 3/9] perf/jit: remove unecessary padding in jitdump file

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 13 Oct 2016 03:59:37 -0700
From:   Stephane Eranian <eranian@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     acme@...nel.org, jolsa@...hat.com, peterz@...radead.org,
        mingo@...e.hu, anton@...abs.org, namhyung@...nel.org
Subject: [PATCH 3/9] perf/jit: remove unecessary padding in jitdump file

This patch removes all the string padding generated in
the jitdump file. There are nonecessary and were adding
unecessary complexity. Modern processors can handle unaligned
accesses quite well. The perf.data/jitdump file are always
postp-processed, no need to add extra complexity for no real
gain.

Signed-off-by: Stephane Eranian <eranian@...gle.com>
---
 tools/perf/jvmti/jvmti_agent.c | 38 +-------------------------------------
 1 file changed, 1 insertion(+), 37 deletions(-)

diff --git a/tools/perf/jvmti/jvmti_agent.c b/tools/perf/jvmti/jvmti_agent.c
index 55daefff0d54..e9651a9d670e 100644
--- a/tools/perf/jvmti/jvmti_agent.c
+++ b/tools/perf/jvmti/jvmti_agent.c
@@ -44,11 +44,6 @@
 static char jit_path[PATH_MAX];
 static void *marker_addr;
 
-/*
- * padding buffer
- */
-static const char pad_bytes[7];
-
 static inline pid_t gettid(void)
 {
 	return (pid_t)syscall(__NR_gettid);
@@ -230,7 +225,6 @@ init_arch_timestamp(void)
 
 void *jvmti_open(void)
 {
-	int pad_cnt;
 	char dump_path[PATH_MAX];
 	struct jitheader header;
 	int fd;
@@ -288,10 +282,6 @@ void *jvmti_open(void)
 	header.total_size = sizeof(header);
 	header.pid        = getpid();
 
-	/* calculate amount of padding '\0' */
-	pad_cnt = PADDING_8ALIGNED(header.total_size);
-	header.total_size += pad_cnt;
-
 	header.timestamp = perf_get_timestamp();
 
 	if (use_arch_timestamp)
@@ -301,13 +291,6 @@ void *jvmti_open(void)
 		warn("jvmti: cannot write dumpfile header");
 		goto error;
 	}
-
-	/* write padding '\0' if necessary */
-	if (pad_cnt && !fwrite(pad_bytes, pad_cnt, 1, fp)) {
-		warn("jvmti: cannot write dumpfile header padding");
-		goto error;
-	}
-
 	return fp;
 error:
 	fclose(fp);
@@ -349,7 +332,6 @@ jvmti_write_code(void *agent, char const *sym,
 	static int code_generation = 1;
 	struct jr_code_load rec;
 	size_t sym_len;
-	size_t padding_count;
 	FILE *fp = agent;
 	int ret = -1;
 
@@ -366,8 +348,6 @@ jvmti_write_code(void *agent, char const *sym,
 
 	rec.p.id           = JIT_CODE_LOAD;
 	rec.p.total_size   = sizeof(rec) + sym_len;
-	padding_count      = PADDING_8ALIGNED(rec.p.total_size);
-	rec.p. total_size += padding_count;
 	rec.p.timestamp    = perf_get_timestamp();
 
 	rec.code_size  = size;
@@ -393,9 +373,6 @@ jvmti_write_code(void *agent, char const *sym,
 	ret = fwrite_unlocked(&rec, sizeof(rec), 1, fp);
 	fwrite_unlocked(sym, sym_len, 1, fp);
 
-	if (padding_count)
-		fwrite_unlocked(pad_bytes, padding_count, 1, fp);
-
 	if (code)
 		fwrite_unlocked(code, size, 1, fp);
 
@@ -412,7 +389,6 @@ jvmti_write_debug_info(void *agent, uint64_t code, const char *file,
 {
 	struct jr_code_debug_info rec;
 	size_t sret, len, size, flen;
-	size_t padding_count;
 	uint64_t addr;
 	const char *fn = file;
 	FILE *fp = agent;
@@ -443,16 +419,10 @@ jvmti_write_debug_info(void *agent, uint64_t code, const char *file,
 	 * int      : line number
 	 * int      : column discriminator
 	 * file[]   : source file name
-	 * padding  : pad to multiple of 8 bytes
 	 */
 	size += nr_lines * sizeof(struct debug_entry);
 	size += flen * nr_lines;
-	/*
-	 * pad to 8 bytes
-	 */
-	padding_count = PADDING_8ALIGNED(size);
-
-	rec.p.total_size = size + padding_count;
+	rec.p.total_size = size;
 
 	/*
 	 * If JVM is multi-threaded, nultiple concurrent calls to agent
@@ -486,12 +456,6 @@ jvmti_write_debug_info(void *agent, uint64_t code, const char *file,
 		if (sret != 1)
 			goto error;
 	}
-	if (padding_count) {
-		sret = fwrite_unlocked(pad_bytes, padding_count, 1, fp);
-		if (sret != 1)
-			goto error;
-	}
-
 	funlockfile(fp);
 	return 0;
 error:
-- 
1.9.1