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 2/9] ARM: assembler: introduce bl_r macro
Date: Mon, 15 Nov 2021 09:47:25 +0100 [thread overview]
Message-ID: <20211115084732.3704393-3-ardb@kernel.org> (raw)
In-Reply-To: <20211115084732.3704393-1-ardb@kernel.org>
Add a bl_r macro that abstract the difference between the ways indirect
calls are performed on older and newer ARM architecture revisions.
The main difference is to prefer blx instructions over explicit LR
assignments when possible, as these tend to confuse the prediction logic
in out-of-order cores when speculating across a function return.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Keith Packard <keithpac@amazon.com>
---
arch/arm/include/asm/assembler.h | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h
index 7d23d4bb2168..870bfaea4318 100644
--- a/arch/arm/include/asm/assembler.h
+++ b/arch/arm/include/asm/assembler.h
@@ -624,4 +624,19 @@ THUMB( orr \reg , \reg , #PSR_T_BIT )
.endif
.endm
+ /*
+ * bl_r - branch and link to register
+ *
+ * @dst: target to branch to
+ * @c: conditional opcode suffix
+ */
+ .macro bl_r, dst:req, c
+ .if __LINUX_ARM_ARCH__ < 6
+ mov\c lr, pc
+ mov\c pc, \dst
+ .else
+ blx\c \dst
+ .endif
+ .endm
+
#endif /* __ASM_ASSEMBLER_H__ */
--
2.30.2
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next prev parent reply other threads:[~2021-11-15 8:49 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 ` Ard Biesheuvel [this message]
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 ` [PATCH v4 8/9] ARM: call_with_stack: add unwind support Ard Biesheuvel
2021-11-15 8:47 ` [PATCH v4 9/9] ARM: run softirqs on the per-CPU IRQ stack Ard Biesheuvel
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