linux-kernel - [RFC PATCH 12/28] x86/pm-trace: Use RIP-relative accesses for .tracedata

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Message-ID: <20240925150059.3955569-42-ardb+git@google.com>
Date: Wed, 25 Sep 2024 17:01:12 +0200
From: Ard Biesheuvel <ardb+git@...gle.com>
To: linux-kernel@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>, x86@...nel.org, "H. Peter Anvin" <hpa@...or.com>, 
	Andy Lutomirski <luto@...nel.org>, Peter Zijlstra <peterz@...radead.org>, Uros Bizjak <ubizjak@...il.com>, 
	Dennis Zhou <dennis@...nel.org>, Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>, 
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Vitaly Kuznetsov <vkuznets@...hat.com>, Juergen Gross <jgross@...e.com>, 
	Boris Ostrovsky <boris.ostrovsky@...cle.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Arnd Bergmann <arnd@...db.de>, 
	Masahiro Yamada <masahiroy@...nel.org>, Kees Cook <kees@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Keith Packard <keithp@...thp.com>, 
	Justin Stitt <justinstitt@...gle.com>, Josh Poimboeuf <jpoimboe@...nel.org>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, Jiri Olsa <jolsa@...nel.org>, 
	Ian Rogers <irogers@...gle.com>, Adrian Hunter <adrian.hunter@...el.com>, 
	Kan Liang <kan.liang@...ux.intel.com>, linux-doc@...r.kernel.org, 
	linux-pm@...r.kernel.org, kvm@...r.kernel.org, xen-devel@...ts.xenproject.org, 
	linux-efi@...r.kernel.org, linux-arch@...r.kernel.org, 
	linux-sparse@...r.kernel.org, linux-kbuild@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, rust-for-linux@...r.kernel.org, 
	llvm@...ts.linux.dev
Subject: [RFC PATCH 12/28] x86/pm-trace: Use RIP-relative accesses for .tracedata

From: Ard Biesheuvel <ardb@...nel.org>

Use RIP-relative accesses and 32-bit offsets for .tracedata, to avoid
the need for relocation fixups at boot time.

Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
---
 arch/x86/include/asm/pm-trace.h | 4 ++--
 drivers/base/power/trace.c      | 6 +++---
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/pm-trace.h b/arch/x86/include/asm/pm-trace.h
index bfa32aa428e5..123faf978473 100644
--- a/arch/x86/include/asm/pm-trace.h
+++ b/arch/x86/include/asm/pm-trace.h
@@ -8,10 +8,10 @@
 do {								\
 	if (pm_trace_enabled) {					\
 		const void *tracedata;				\
-		asm volatile(_ASM_MOV " $1f,%0\n"		\
+		asm volatile("lea " _ASM_RIP(1f) ", %0\n"	\
 			     ".section .tracedata,\"a\"\n"	\
 			     "1:\t.word %c1\n\t"		\
-			     _ASM_PTR " %c2\n"			\
+			     ".long %c2 - .\n"			\
 			     ".previous"			\
 			     :"=r" (tracedata)			\
 			     : "i" (__LINE__), "i" (__FILE__));	\
diff --git a/drivers/base/power/trace.c b/drivers/base/power/trace.c
index cd6e559648b2..686a0276ccfc 100644
--- a/drivers/base/power/trace.c
+++ b/drivers/base/power/trace.c
@@ -167,7 +167,7 @@ EXPORT_SYMBOL(set_trace_device);
 void generate_pm_trace(const void *tracedata, unsigned int user)
 {
 	unsigned short lineno = *(unsigned short *)tracedata;
-	const char *file = *(const char **)(tracedata + 2);
+	const char *file = offset_to_ptr((int *)(tracedata + 2));
 	unsigned int user_hash_value, file_hash_value;
 
 	if (!x86_platform.legacy.rtc)
@@ -187,9 +187,9 @@ static int show_file_hash(unsigned int value)
 
 	match = 0;
 	for (tracedata = __tracedata_start ; tracedata < __tracedata_end ;
-			tracedata += 2 + sizeof(unsigned long)) {
+			tracedata += 2 + sizeof(int)) {
 		unsigned short lineno = *(unsigned short *)tracedata;
-		const char *file = *(const char **)(tracedata + 2);
+		const char *file = offset_to_ptr((int *)(tracedata + 2));
 		unsigned int hash = hash_string(lineno, file, FILEHASH);
 		if (hash != value)
 			continue;
-- 
2.46.0.792.g87dc391469-goog