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From: Ard Biesheuvel <ardb@kernel.org>
To: linux@armlinux.org.uk
Cc: linux-arm-kernel@lists.infradead.org,
	Ard Biesheuvel <ardb@kernel.org>,
	Steven Rostedt <rostedt@goodmis.org>,
	Sudeep Holla <sudeep.holla@arm.com>,
	Cristian Marussi <cristian.marussi@arm.com>,
	Nathan Chancellor <nathan@kernel.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Arnd Bergmann <arnd@arndb.de>,
	Linus Walleij <linus.walleij@linaro.org>,
	Masami Hiramatsu <mhiramat@kernel.org>
Subject: [PATCH v3 09/13] ARM: kprobes: treat R7 as the frame pointer register in Thumb2 builds
Date: Thu,  3 Feb 2022 09:22:00 +0100	[thread overview]
Message-ID: <20220203082204.1176734-10-ardb@kernel.org> (raw)
In-Reply-To: <20220203082204.1176734-1-ardb@kernel.org>

Thumb2 code uses R7 as the frame pointer rather than R11, because the
opcodes to access it are generally shorter.

This means that there are cases where we cannot simply add it to the
clobber list of an asm() block, but need to preserve/restore it
explicitly, or the compiler may complain in some cases (e.g., Clang
builds with ftrace enabled).

Since R11 is not special in that case, clobber it instead, and use it to
preserve/restore the value of R7.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 arch/arm/probes/kprobes/actions-common.c |  8 +++++---
 arch/arm/probes/kprobes/actions-thumb.c  | 16 ++++++++++++----
 2 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/arch/arm/probes/kprobes/actions-common.c b/arch/arm/probes/kprobes/actions-common.c
index 836aebe596cd..79171344dbeb 100644
--- a/arch/arm/probes/kprobes/actions-common.c
+++ b/arch/arm/probes/kprobes/actions-common.c
@@ -84,7 +84,8 @@ emulate_generic_r0_12_noflags(probes_opcode_t insn,
 	register void *rfn asm("lr") = asi->insn_fn;
 
 	__asm__ __volatile__ (
-		"stmdb	sp!, {%[regs], r11}	\n\t"
+ARM(		"stmdb	sp!, {%[regs], r11}	\n\t"	)
+THUMB(		"stmdb	sp!, {%[regs], r7}	\n\t"	)
 		"ldmia	%[regs], {r0-r12}	\n\t"
 #if __LINUX_ARM_ARCH__ >= 6
 		"blx	%[fn]			\n\t"
@@ -96,10 +97,11 @@ emulate_generic_r0_12_noflags(probes_opcode_t insn,
 #endif
 		"ldr	lr, [sp], #4		\n\t" /* lr = regs */
 		"stmia	lr, {r0-r12}		\n\t"
-		"ldr	r11, [sp], #4		\n\t"
+ARM(		"ldr	r11, [sp], #4		\n\t"	)
+THUMB(		"ldr	r7, [sp], #4		\n\t"	)
 		: [regs] "=r" (rregs), [fn] "=r" (rfn)
 		: "0" (rregs), "1" (rfn)
-		: "r0", "r2", "r3", "r4", "r5", "r6", "r7",
+		: "r0", "r2", "r3", "r4", "r5", "r6", ARM("r7") THUMB("r11"),
 		  "r8", "r9", "r10", "r12", "memory", "cc"
 		);
 }
diff --git a/arch/arm/probes/kprobes/actions-thumb.c b/arch/arm/probes/kprobes/actions-thumb.c
index 7884fcb81c26..51624fc263fc 100644
--- a/arch/arm/probes/kprobes/actions-thumb.c
+++ b/arch/arm/probes/kprobes/actions-thumb.c
@@ -447,14 +447,16 @@ t16_emulate_loregs(probes_opcode_t insn,
 
 	__asm__ __volatile__ (
 		"msr	cpsr_fs, %[oldcpsr]	\n\t"
+		"mov	r11, r7			\n\t"
 		"ldmia	%[regs], {r0-r7}	\n\t"
 		"blx	%[fn]			\n\t"
 		"stmia	%[regs], {r0-r7}	\n\t"
+		"mov	r7, r11			\n\t"
 		"mrs	%[newcpsr], cpsr	\n\t"
 		: [newcpsr] "=r" (newcpsr)
 		: [oldcpsr] "r" (oldcpsr), [regs] "r" (regs),
 		  [fn] "r" (asi->insn_fn)
-		: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
+		: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r11",
 		  "lr", "memory", "cc"
 		);
 
@@ -524,14 +526,16 @@ t16_emulate_push(probes_opcode_t insn,
 		struct arch_probes_insn *asi, struct pt_regs *regs)
 {
 	__asm__ __volatile__ (
+		"mov	r11, r7			\n\t"
 		"ldr	r9, [%[regs], #13*4]	\n\t"
 		"ldr	r8, [%[regs], #14*4]	\n\t"
 		"ldmia	%[regs], {r0-r7}	\n\t"
 		"blx	%[fn]			\n\t"
 		"str	r9, [%[regs], #13*4]	\n\t"
+		"mov	r7, r11			\n\t"
 		:
 		: [regs] "r" (regs), [fn] "r" (asi->insn_fn)
-		: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r8", "r9",
+		: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r8", "r9", "r11",
 		  "lr", "memory", "cc"
 		);
 }
@@ -558,14 +562,16 @@ t16_emulate_pop_nopc(probes_opcode_t insn,
 		struct arch_probes_insn *asi, struct pt_regs *regs)
 {
 	__asm__ __volatile__ (
+		"mov	r11, r7			\n\t"
 		"ldr	r9, [%[regs], #13*4]	\n\t"
 		"ldmia	%[regs], {r0-r7}	\n\t"
 		"blx	%[fn]			\n\t"
 		"stmia	%[regs], {r0-r7}	\n\t"
 		"str	r9, [%[regs], #13*4]	\n\t"
+		"mov	r7, r11			\n\t"
 		:
 		: [regs] "r" (regs), [fn] "r" (asi->insn_fn)
-		: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r9",
+		: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r9", "r11",
 		  "lr", "memory", "cc"
 		);
 }
@@ -577,14 +583,16 @@ t16_emulate_pop_pc(probes_opcode_t insn,
 	register unsigned long pc asm("r8");
 
 	__asm__ __volatile__ (
+		"mov	r11, r7			\n\t"
 		"ldr	r9, [%[regs], #13*4]	\n\t"
 		"ldmia	%[regs], {r0-r7}	\n\t"
 		"blx	%[fn]			\n\t"
 		"stmia	%[regs], {r0-r7}	\n\t"
 		"str	r9, [%[regs], #13*4]	\n\t"
+		"mov	r7, r11			\n\t"
 		: "=r" (pc)
 		: [regs] "r" (regs), [fn] "r" (asi->insn_fn)
-		: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7", "r9",
+		: "r0", "r1", "r2", "r3", "r4", "r5", "r6", "r9", "r11",
 		  "lr", "memory", "cc"
 		);
 
-- 
2.30.2


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  parent reply	other threads:[~2022-02-03  8:27 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-02-03  8:21 [PATCH v3 00/13] ARM: ftrace fixes and cleanups Ard Biesheuvel
2022-02-03  8:21 ` [PATCH v3 01/13] ARM: ftrace: ensure that ADR takes the Thumb bit into account Ard Biesheuvel
2022-02-03  8:21 ` [PATCH v3 02/13] ARM: ftrace: use ADD not POP to counter PUSH at entry Ard Biesheuvel
2022-02-03  8:21 ` [PATCH v3 03/13] ARM: ftrace: use trampolines to keep .init.text in branching range Ard Biesheuvel
2022-02-03  8:21 ` [PATCH v3 04/13] ARM: ftrace: avoid redundant loads or clobbering IP Ard Biesheuvel
2022-02-03  8:21 ` [PATCH v3 05/13] ARM: ftrace: avoid unnecessary literal loads Ard Biesheuvel
2022-02-03  8:21 ` [PATCH v3 06/13] ARM: ftrace: enable HAVE_FUNCTION_GRAPH_FP_TEST Ard Biesheuvel
2022-02-03  8:21 ` [PATCH v3 07/13] ARM: unwind: track location of LR value in stack frame Ard Biesheuvel
2022-02-07 18:14   ` Nick Desaulniers
2022-02-03  8:21 ` [PATCH v3 08/13] ARM: ftrace: enable the graph tracer with the EABI unwinder Ard Biesheuvel
2022-02-03  9:16   ` Arnd Bergmann
2022-02-03  9:41     ` Ard Biesheuvel
2022-02-03 16:09     ` Nathan Chancellor
2022-02-03 16:11       ` Ard Biesheuvel
2022-02-03  8:22 ` Ard Biesheuvel [this message]
2022-02-03  8:22 ` [PATCH v3 10/13] drivers/firmware/scmi: disable ftrace for Clang Thumb2 builds Ard Biesheuvel
2022-02-07 18:28   ` Sudeep Holla
2022-02-08 21:18     ` Ard Biesheuvel
2022-02-11  9:56   ` Sudeep Holla
2022-02-03  8:22 ` [PATCH v3 11/13] ARM: cacheflush: avoid clobbering the frame pointer Ard Biesheuvel
2022-02-07 19:12   ` Nick Desaulniers
2022-02-08 10:08     ` Ard Biesheuvel
2022-02-08 22:34       ` Nick Desaulniers
2022-02-08 22:39         ` Nick Desaulniers
2022-02-03  8:22 ` [PATCH v3 12/13] ARM: mach-bcm: disable ftrace in SMC invocation routines Ard Biesheuvel
2022-02-03 20:39   ` Nick Desaulniers
2022-02-03  8:22 ` [PATCH v3 13/13] Revert "ARM: 9144/1: forbid ftrace with clang and thumb2_kernel" Ard Biesheuvel

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