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From: Nathan Chancellor <nathan@kernel.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Christophe Leroy <christophe.leroy@csgroup.eu>,
	Alexey Kardashevskiy <aik@ozlabs.ru>,
	Nick Desaulniers <ndesaulniers@google.com>,
	Tom Rix <trix@redhat.com>,
	linuxppc-dev@lists.ozlabs.org, llvm@lists.linux.dev,
	patches@lists.linux.dev, Nathan Chancellor <nathan@kernel.org>
Subject: [PATCH v2 1/2] powerpc/vdso: Remove unused ENTRY in linker scripts
Date: Wed, 11 May 2022 11:50:00 -0700	[thread overview]
Message-ID: <20220511185001.3269404-2-nathan@kernel.org> (raw)
In-Reply-To: <20220511185001.3269404-1-nathan@kernel.org>

When linking vdso{32,64}.so.dbg with ld.lld, there is a warning about
not finding _start for the starting address:

  ld.lld: warning: cannot find entry symbol _start; not setting start address
  ld.lld: warning: cannot find entry symbol _start; not setting start address

Looking at GCC + GNU ld, the entry point address is 0x0:

  $ llvm-readelf -h vdso{32,64}.so.dbg &| rg "(File|Entry point address):"
  File: vdso32.so.dbg
    Entry point address:               0x0
  File: vdso64.so.dbg
    Entry point address:               0x0

This matches what ld.lld emits:

  $ powerpc64le-linux-gnu-readelf -p .comment vdso{32,64}.so.dbg

  File: vdso32.so.dbg

  String dump of section '.comment':
    [     0]  Linker: LLD 14.0.0
    [    14]  clang version 14.0.0 (Fedora 14.0.0-1.fc37)

  File: vdso64.so.dbg

  String dump of section '.comment':
    [     0]  Linker: LLD 14.0.0
    [    14]  clang version 14.0.0 (Fedora 14.0.0-1.fc37)

  $ llvm-readelf -h vdso{32,64}.so.dbg &| rg "(File|Entry point address):"
  File: vdso32.so.dbg
    Entry point address:               0x0
  File: vdso64.so.dbg
    Entry point address:               0x0

Remove ENTRY to remove the warning, as it is unnecessary for the vDSO to
function correctly.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/powerpc/kernel/vdso/vdso32.lds.S | 1 -
 arch/powerpc/kernel/vdso/vdso64.lds.S | 1 -
 2 files changed, 2 deletions(-)

diff --git a/arch/powerpc/kernel/vdso/vdso32.lds.S b/arch/powerpc/kernel/vdso/vdso32.lds.S
index 58e0099f70f4..e0d19d74455f 100644
--- a/arch/powerpc/kernel/vdso/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso/vdso32.lds.S
@@ -13,7 +13,6 @@ OUTPUT_FORMAT("elf32-powerpcle", "elf32-powerpcle", "elf32-powerpcle")
 OUTPUT_FORMAT("elf32-powerpc", "elf32-powerpc", "elf32-powerpc")
 #endif
 OUTPUT_ARCH(powerpc:common)
-ENTRY(_start)
 
 SECTIONS
 {
diff --git a/arch/powerpc/kernel/vdso/vdso64.lds.S b/arch/powerpc/kernel/vdso/vdso64.lds.S
index 0288cad428b0..1a4a7bc4c815 100644
--- a/arch/powerpc/kernel/vdso/vdso64.lds.S
+++ b/arch/powerpc/kernel/vdso/vdso64.lds.S
@@ -13,7 +13,6 @@ OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle")
 OUTPUT_FORMAT("elf64-powerpc", "elf64-powerpc", "elf64-powerpc")
 #endif
 OUTPUT_ARCH(powerpc:common64)
-ENTRY(_start)
 
 SECTIONS
 {
-- 
2.36.1


WARNING: multiple messages have this Message-ID (diff)
From: Nathan Chancellor <nathan@kernel.org>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: Alexey Kardashevskiy <aik@ozlabs.ru>,
	llvm@lists.linux.dev, Nick Desaulniers <ndesaulniers@google.com>,
	patches@lists.linux.dev, Nathan Chancellor <nathan@kernel.org>,
	Paul Mackerras <paulus@samba.org>, Tom Rix <trix@redhat.com>,
	linuxppc-dev@lists.ozlabs.org
Subject: [PATCH v2 1/2] powerpc/vdso: Remove unused ENTRY in linker scripts
Date: Wed, 11 May 2022 11:50:00 -0700	[thread overview]
Message-ID: <20220511185001.3269404-2-nathan@kernel.org> (raw)
In-Reply-To: <20220511185001.3269404-1-nathan@kernel.org>

When linking vdso{32,64}.so.dbg with ld.lld, there is a warning about
not finding _start for the starting address:

  ld.lld: warning: cannot find entry symbol _start; not setting start address
  ld.lld: warning: cannot find entry symbol _start; not setting start address

Looking at GCC + GNU ld, the entry point address is 0x0:

  $ llvm-readelf -h vdso{32,64}.so.dbg &| rg "(File|Entry point address):"
  File: vdso32.so.dbg
    Entry point address:               0x0
  File: vdso64.so.dbg
    Entry point address:               0x0

This matches what ld.lld emits:

  $ powerpc64le-linux-gnu-readelf -p .comment vdso{32,64}.so.dbg

  File: vdso32.so.dbg

  String dump of section '.comment':
    [     0]  Linker: LLD 14.0.0
    [    14]  clang version 14.0.0 (Fedora 14.0.0-1.fc37)

  File: vdso64.so.dbg

  String dump of section '.comment':
    [     0]  Linker: LLD 14.0.0
    [    14]  clang version 14.0.0 (Fedora 14.0.0-1.fc37)

  $ llvm-readelf -h vdso{32,64}.so.dbg &| rg "(File|Entry point address):"
  File: vdso32.so.dbg
    Entry point address:               0x0
  File: vdso64.so.dbg
    Entry point address:               0x0

Remove ENTRY to remove the warning, as it is unnecessary for the vDSO to
function correctly.

Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Tested-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 arch/powerpc/kernel/vdso/vdso32.lds.S | 1 -
 arch/powerpc/kernel/vdso/vdso64.lds.S | 1 -
 2 files changed, 2 deletions(-)

diff --git a/arch/powerpc/kernel/vdso/vdso32.lds.S b/arch/powerpc/kernel/vdso/vdso32.lds.S
index 58e0099f70f4..e0d19d74455f 100644
--- a/arch/powerpc/kernel/vdso/vdso32.lds.S
+++ b/arch/powerpc/kernel/vdso/vdso32.lds.S
@@ -13,7 +13,6 @@ OUTPUT_FORMAT("elf32-powerpcle", "elf32-powerpcle", "elf32-powerpcle")
 OUTPUT_FORMAT("elf32-powerpc", "elf32-powerpc", "elf32-powerpc")
 #endif
 OUTPUT_ARCH(powerpc:common)
-ENTRY(_start)
 
 SECTIONS
 {
diff --git a/arch/powerpc/kernel/vdso/vdso64.lds.S b/arch/powerpc/kernel/vdso/vdso64.lds.S
index 0288cad428b0..1a4a7bc4c815 100644
--- a/arch/powerpc/kernel/vdso/vdso64.lds.S
+++ b/arch/powerpc/kernel/vdso/vdso64.lds.S
@@ -13,7 +13,6 @@ OUTPUT_FORMAT("elf64-powerpcle", "elf64-powerpcle", "elf64-powerpcle")
 OUTPUT_FORMAT("elf64-powerpc", "elf64-powerpc", "elf64-powerpc")
 #endif
 OUTPUT_ARCH(powerpc:common64)
-ENTRY(_start)
 
 SECTIONS
 {
-- 
2.36.1


  reply	other threads:[~2022-05-11 18:50 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-11 18:49 [PATCH v2 0/2] Link the PowerPC vDSO with ld.lld Nathan Chancellor
2022-05-11 18:49 ` Nathan Chancellor
2022-05-11 18:50 ` Nathan Chancellor [this message]
2022-05-11 18:50   ` [PATCH v2 1/2] powerpc/vdso: Remove unused ENTRY in linker scripts Nathan Chancellor
2022-05-11 18:50 ` [PATCH v2 2/2] powerpc/vdso: Link with ld.lld when requested Nathan Chancellor
2022-05-11 18:50   ` Nathan Chancellor
2022-05-24 11:08 ` [PATCH v2 0/2] Link the PowerPC vDSO with ld.lld Michael Ellerman
2022-05-24 11:08   ` Michael Ellerman

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