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From: Ard Biesheuvel <ardb@kernel.org>
To: linux-arm-kernel@lists.infradead.org
Cc: Ard Biesheuvel <ardb@kernel.org>,
	Russell King <linux@armlinux.org.uk>,
	Arnd Bergmann <arnd@arndb.de>, Kees Cook <keescook@chromium.org>,
	Keith Packard <keithpac@amazon.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Nicolas Pitre <nico@fluxnic.net>
Subject: [PATCH v4 8/9] ARM: call_with_stack: add unwind support
Date: Mon, 15 Nov 2021 09:47:31 +0100	[thread overview]
Message-ID: <20211115084732.3704393-9-ardb@kernel.org> (raw)
In-Reply-To: <20211115084732.3704393-1-ardb@kernel.org>

Restructure the code and add the unwind annotations so that both the
frame pointer unwinder as well as the EHABI unwind info based unwinder
will be able to follow the call stack through call_with_stack().

Since GCC and Clang use different formats for the stack frame, two
methods are implemented: a GCC version that pushes fp, sp, lr and pc for
compatibility with the frame pointer unwinder, and a second version that
works with Clang, as well as with the EHABI unwinder both in ARM and
Thumb2 modes.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
---
 arch/arm/lib/call_with_stack.S | 33 +++++++++++++++-----
 1 file changed, 25 insertions(+), 8 deletions(-)

diff --git a/arch/arm/lib/call_with_stack.S b/arch/arm/lib/call_with_stack.S
index 28b0341ae786..0a268a6c513c 100644
--- a/arch/arm/lib/call_with_stack.S
+++ b/arch/arm/lib/call_with_stack.S
@@ -8,25 +8,42 @@
 
 #include <linux/linkage.h>
 #include <asm/assembler.h>
+#include <asm/unwind.h>
 
 /*
  * void call_with_stack(void (*fn)(void *), void *arg, void *sp)
  *
  * Change the stack to that pointed at by sp, then invoke fn(arg) with
  * the new stack.
+ *
+ * The sequence below follows the APCS frame convention for frame pointer
+ * unwinding, and implements the unwinder annotations needed by the EABI
+ * unwinder.
  */
-ENTRY(call_with_stack)
-	str	sp, [r2, #-4]!
-	str	lr, [r2, #-4]!
 
+ENTRY(call_with_stack)
+#if defined(CONFIG_UNWINDER_FRAME_POINTER) && defined(CONFIG_CC_IS_GCC)
+	mov	ip, sp
+	push	{fp, ip, lr, pc}
+	sub	fp, ip, #4
+#else
+UNWIND( .fnstart		)
+UNWIND( .save	{fpreg, lr}	)
+	push	{fpreg, lr}
+UNWIND( .setfp	fpreg, sp	)
+	mov	fpreg, sp
+#endif
 	mov	sp, r2
 	mov	r2, r0
 	mov	r0, r1
 
-	badr	lr, 1f
-	ret	r2
+	bl_r	r2
 
-1:	ldr	lr, [sp]
-	ldr	sp, [sp, #4]
-	ret	lr
+#if defined(CONFIG_UNWINDER_FRAME_POINTER) && defined(CONFIG_CC_IS_GCC)
+	ldmdb	fp, {fp, sp, pc}
+#else
+	mov	sp, fpreg
+	pop	{fpreg, pc}
+UNWIND( .fnend			)
+#endif
 ENDPROC(call_with_stack)
-- 
2.30.2


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  parent reply	other threads:[~2021-11-15  8:51 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-15  8:47 [PATCH v4 0/9] ARM: add support for IRQ stacks Ard Biesheuvel
2021-11-15  8:47 ` [PATCH v4 1/9] ARM: remove some dead code Ard Biesheuvel
2021-11-15  8:47 ` [PATCH v4 2/9] ARM: assembler: introduce bl_r macro Ard Biesheuvel
2021-11-15  8:47 ` [PATCH v4 3/9] ARM: unwind: support unwinding across multiple stacks Ard Biesheuvel
2021-11-15  8:47 ` [PATCH v4 4/9] ARM: export dump_mem() to other objects Ard Biesheuvel
2021-11-15  8:47 ` [PATCH v4 5/9] ARM: unwind: dump exception stack from calling frame Ard Biesheuvel
2021-11-15  8:47 ` [PATCH v4 6/9] ARM: backtrace-clang: avoid crash on bogus frame pointer Ard Biesheuvel
2021-11-15  8:47 ` [PATCH v4 7/9] ARM: implement IRQ stacks Ard Biesheuvel
2021-11-15  8:47 ` Ard Biesheuvel [this message]
2021-11-15  8:47 ` [PATCH v4 9/9] ARM: run softirqs on the per-CPU IRQ stack Ard Biesheuvel

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