From: Catalin Marinas <catalin.marinas@arm.com>
To: Peter Smith <Peter.Smith@arm.com>
Cc: Nick Desaulniers <ndesaulniers@google.com>,
Robin Murphy <Robin.Murphy@arm.com>,
Will Deacon <will@kernel.org>,
Naohiro Aota <naohiro.aota@wdc.com>,
Stephen Boyd <swboyd@google.com>,
Masahiro Yamada <masahiroy@kernel.org>,
LKML <linux-kernel@vger.kernel.org>,
Manoj Gupta <manojgupta@google.com>,
Luis Lozano <llozano@google.com>,
Nathan Chancellor <natechancellor@gmail.com>,
Vincenzo Frascino <Vincenzo.Frascino@arm.com>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Kristof Beyls <Kristof.Beyls@arm.com>,
Victor Campos <Victor.Campos@arm.com>,
"david.spickett@linaro.org" <david.spickett@linaro.org>,
Arnd Bergmann <arnd@arndb.de>
Subject: Re: [PATCH] arm64: vdso32: force vdso32 to be compiled as -marm
Date: Thu, 28 May 2020 10:41:54 +0100 [thread overview]
Message-ID: <20200528094154.GB2961@gaia> (raw)
In-Reply-To: <VI1PR08MB319868AFBEDCD0925C53701AF88E0@VI1PR08MB3198.eurprd08.prod.outlook.com>
On Thu, May 28, 2020 at 09:05:08AM +0100, Peter Smith wrote:
> I suggest using Arm if you need a frame pointer, and disable the
> frame pointer if you want/need to use Thumb. My understanding is that
> runtime unwinding using the frame pointer in Thumb is already difficult
> due to Arm and Thumb functions using different registers for the frame
> pointer.
IIRC from the Thumb-2 kernel porting days, even in the absence of
ARM/Thumb interworking, the Thumb-2 frame pointer was pretty useless for
unwinding since it points to the bottom of the current stack frame (the
reason I think is that some LDR/STR instructions with negative indexing
are not available). So finding the previous frame pointer was not
possible and had to rely on the exception unwinding information.
--
Catalin
next prev parent reply other threads:[~2020-05-28 9:42 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-26 17:31 [PATCH] arm64: vdso32: force vdso32 to be compiled as -marm Nick Desaulniers
2020-05-26 18:55 ` Stephen Boyd
2020-05-26 20:45 ` Will Deacon
2020-05-27 13:53 ` Dave Martin
2020-05-27 17:58 ` Nick Desaulniers
2020-05-27 13:45 ` Robin Murphy
2020-05-27 17:55 ` Nick Desaulniers
2020-05-27 18:08 ` Will Deacon
2020-05-27 18:17 ` Nick Desaulniers
2020-05-28 7:20 ` Will Deacon
2020-06-08 20:57 ` [PATCH v2] arm64: vdso32: add CONFIG_THUMB2_COMPAT_VDSO Nick Desaulniers
2020-06-09 20:35 ` Catalin Marinas
2020-06-09 23:55 ` Nick Desaulniers
2020-06-10 8:47 ` Will Deacon
2020-06-10 10:29 ` Catalin Marinas
2020-06-10 10:32 ` Will Deacon
2020-06-10 11:21 ` Will Deacon
2020-05-27 19:28 ` [PATCH] arm64: vdso32: force vdso32 to be compiled as -marm Robin Murphy
2020-05-27 20:02 ` Robin Murphy
2020-05-27 20:14 ` Nick Desaulniers
2020-05-27 20:31 ` Nick Desaulniers
2020-05-27 21:47 ` Nick Desaulniers
2020-05-28 8:05 ` Peter Smith
2020-05-28 9:41 ` Catalin Marinas [this message]
2020-05-28 19:06 ` Nick Desaulniers
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