public inbox for devel@edk2.groups.io
 help / color / mirror / Atom feed
From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: edk2-devel@lists.01.org
Cc: lersek@redhat.com, leif.lindholm@linaro.org, philmd@redhat.com,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>
Subject: [PATCH 2/2] ArmVirtPkg/PrePi: clear frame pointer in startup code
Date: Fri, 16 Nov 2018 14:55:58 -0800	[thread overview]
Message-ID: <20181116225558.27720-3-ard.biesheuvel@linaro.org> (raw)
In-Reply-To: <20181116225558.27720-1-ard.biesheuvel@linaro.org>

When setting up the stack in the startup code and jumping into C code
for the first time, ensure that the frame pointer register is cleared
so that backtraces terminate correctly. Otherwise, output like the
below is shown when encountering an exception on a DEBUG build:

  Synchronous Exception at 0x0000000078A14780
  PC 0x000078A14780 (0x000078A00000+0x00014780) [ 0] ArmVeNorFlashDxe.dll
  PC 0x000078A10634 (0x000078A00000+0x00010634) [ 0] ArmVeNorFlashDxe.dll
  PC 0x000078A11CF0 (0x000078A00000+0x00011CF0) [ 0] ArmVeNorFlashDxe.dll
  PC 0x000078A11DD0 (0x000078A00000+0x00011DD0) [ 0] ArmVeNorFlashDxe.dll
  PC 0x00007BC9D87C (0x00007BC98000+0x0000587C) [ 1] PartitionDxe.dll
  PC 0x00007BC99B3C (0x00007BC98000+0x00001B3C) [ 1] PartitionDxe.dll
  PC 0x00007F362F50 (0x00007F359000+0x00009F50) [ 2] DxeCore.dll
  PC 0x00007BD63BB0 (0x00007BD5B000+0x00008BB0) [ 3] BdsDxe.dll
  PC 0x00007BD6EE00 (0x00007BD5B000+0x00013E00) [ 3] BdsDxe.dll
  PC 0x00007BD67C70 (0x00007BD5B000+0x0000CC70) [ 3] BdsDxe.dll
  PC 0x00007F3724F0 (0x00007F359000+0x000194F0) [ 4] DxeCore.dll
  PC 0x00004008FC30
  PC 0x000040090130
  PC 0x5800F6025800F5E1

  Recursive exception occurred while dumping the CPU state

which is rather unhelpful, given that this prevent the remaining debug
output from being printed (register dump, stack dump, fault related
system registers etc)

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
 ArmVirtPkg/PrePi/AArch64/ModuleEntryPoint.S | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/ArmVirtPkg/PrePi/AArch64/ModuleEntryPoint.S b/ArmVirtPkg/PrePi/AArch64/ModuleEntryPoint.S
index 891cf1fcab40..86b9fbee6e67 100644
--- a/ArmVirtPkg/PrePi/AArch64/ModuleEntryPoint.S
+++ b/ArmVirtPkg/PrePi/AArch64/ModuleEntryPoint.S
@@ -121,6 +121,9 @@ _GetStackBase:
   mov   x1, x21
   mov   x2, x22
 
+  // Set the frame pointer to 0x0 so any backtraces terminate here
+  mov   x29, xzr
+
   // Jump to PrePiCore C code
   //    x0 = MpId
   //    x1 = UefiMemoryBase
-- 
2.17.1



  parent reply	other threads:[~2018-11-16 22:56 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-16 22:55 [PATCH 0/2] Clear frame pointer in startup code on AARCH64 systems Ard Biesheuvel
2018-11-16 22:55 ` [PATCH 1/2] ArmPlatformPkg: clear frame pointer in startup code Ard Biesheuvel
2018-11-16 22:55 ` Ard Biesheuvel [this message]
2018-11-19 18:53 ` [PATCH 0/2] Clear frame pointer in startup code on AARCH64 systems Laszlo Ersek
2018-11-19 18:56 ` Leif Lindholm
2018-11-19 19:28   ` Ard Biesheuvel

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-list from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20181116225558.27720-3-ard.biesheuvel@linaro.org \
    --to=devel@edk2.groups.io \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox