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From: Sedat Dilek <sedat.dilek@gmail.com>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Nick Desaulniers <ndesaulniers@google.com>,
	Fangrui Song <maskray@google.com>,
	Dmitry Golovin <dima@golovin.in>,
	Clang-Built-Linux ML <clang-built-linux@googlegroups.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Masahiro Yamada <masahiroy@kernel.org>,
	Daniel Kiper <daniel.kiper@oracle.com>,
	Kees Cook <keescook@chromium.org>,
	Nathan Chancellor <natechancellor@gmail.com>,
	Arnd Bergmann <arnd@arndb.de>, "H . J . Lu" <hjl@sourceware.org>,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v5 6/7] x86/boot: Remove run-time relocations from head_{32,64}.S
Date: Wed, 15 Jul 2020 10:58:00 +0200	[thread overview]
Message-ID: <CA+icZUXDoeHEcFurBVTv-JMR2xR6oj500n=fVSrN56_KOHiHcw@mail.gmail.com> (raw)
In-Reply-To: <20200715004133.1430068-7-nivedita@alum.mit.edu>

On Wed, Jul 15, 2020 at 2:41 AM Arvind Sankar <nivedita@alum.mit.edu> wrote:
>
> The BFD linker generates run-time relocations for z_input_len and
> z_output_len, even though they are absolute symbols.
>
> This is fixed for binutils-2.35 [1]. Work around this for earlier
> versions by defining two variables input_len and output_len in addition
> to the symbols, and use them via position-independent references.
>
> This eliminates the last two run-time relocations in the head code and
> allows us to drop the -z noreloc-overflow flag to the linker.
>
> Move the -pie and --no-dynamic-linker LDFLAGS to LDFLAGS_vmlinux instead
> of KBUILD_LDFLAGS. There shouldn't be anything else getting linked, but
> this is the more logical location for these flags, and modversions might
> call the linker if an EXPORT_SYMBOL is left over accidentally in one of
> the decompressors.
>

Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reported-by: Sedat Dilek <sedat.dilek@gmail.com>

Reported breakage with LLD in previous patchset version.

- Sedat -

> [1] https://sourceware.org/bugzilla/show_bug.cgi?id=25754
>
> Reviewed-by: Kees Cook <keescook@chromium.org>
> Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
> Reviewed-by: Fangrui Song <maskray@google.com>
> Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
> ---
>  arch/x86/boot/compressed/Makefile  | 12 ++----------
>  arch/x86/boot/compressed/head_32.S | 17 ++++++++---------
>  arch/x86/boot/compressed/head_64.S |  4 ++--
>  arch/x86/boot/compressed/mkpiggy.c |  6 ++++++
>  4 files changed, 18 insertions(+), 21 deletions(-)
>
> diff --git a/arch/x86/boot/compressed/Makefile b/arch/x86/boot/compressed/Makefile
> index c829d874dcac..ae2c0dc98a6a 100644
> --- a/arch/x86/boot/compressed/Makefile
> +++ b/arch/x86/boot/compressed/Makefile
> @@ -51,16 +51,8 @@ UBSAN_SANITIZE :=n
>  KBUILD_LDFLAGS := -m elf_$(UTS_MACHINE)
>  # Compressed kernel should be built as PIE since it may be loaded at any
>  # address by the bootloader.
> -ifeq ($(CONFIG_X86_32),y)
> -KBUILD_LDFLAGS += $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
> -else
> -# To build 64-bit compressed kernel as PIE, we disable relocation
> -# overflow check to avoid relocation overflow error with a new linker
> -# command-line option, -z noreloc-overflow.
> -KBUILD_LDFLAGS += $(shell $(LD) --help 2>&1 | grep -q "\-z noreloc-overflow" \
> -       && echo "-z noreloc-overflow -pie --no-dynamic-linker")
> -endif
> -LDFLAGS_vmlinux := -T
> +LDFLAGS_vmlinux := $(call ld-option, -pie) $(call ld-option, --no-dynamic-linker)
> +LDFLAGS_vmlinux += -T
>
>  hostprogs      := mkpiggy
>  HOST_EXTRACFLAGS += -I$(srctree)/tools/include
> diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
> index 8c1a4f5610f5..659fad53ca82 100644
> --- a/arch/x86/boot/compressed/head_32.S
> +++ b/arch/x86/boot/compressed/head_32.S
> @@ -178,18 +178,17 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
>  /*
>   * Do the extraction, and jump to the new kernel..
>   */
> -                               /* push arguments for extract_kernel: */
> -       pushl   $z_output_len   /* decompressed length, end of relocs */
> +       /* push arguments for extract_kernel: */
>
> -       pushl   %ebp            /* output address */
> -
> -       pushl   $z_input_len    /* input_len */
> +       pushl   output_len@GOTOFF(%ebx) /* decompressed length, end of relocs */
> +       pushl   %ebp                    /* output address */
> +       pushl   input_len@GOTOFF(%ebx)  /* input_len */
>         leal    input_data@GOTOFF(%ebx), %eax
> -       pushl   %eax            /* input_data */
> +       pushl   %eax                    /* input_data */
>         leal    boot_heap@GOTOFF(%ebx), %eax
> -       pushl   %eax            /* heap area */
> -       pushl   %esi            /* real mode pointer */
> -       call    extract_kernel  /* returns kernel location in %eax */
> +       pushl   %eax                    /* heap area */
> +       pushl   %esi                    /* real mode pointer */
> +       call    extract_kernel          /* returns kernel location in %eax */
>         addl    $24, %esp
>
>  /*
> diff --git a/arch/x86/boot/compressed/head_64.S b/arch/x86/boot/compressed/head_64.S
> index 11429092c224..9e46729cf162 100644
> --- a/arch/x86/boot/compressed/head_64.S
> +++ b/arch/x86/boot/compressed/head_64.S
> @@ -534,9 +534,9 @@ SYM_FUNC_START_LOCAL_NOALIGN(.Lrelocated)
>         movq    %rsi, %rdi              /* real mode address */
>         leaq    boot_heap(%rip), %rsi   /* malloc area for uncompression */
>         leaq    input_data(%rip), %rdx  /* input_data */
> -       movl    $z_input_len, %ecx      /* input_len */
> +       movl    input_len(%rip), %ecx   /* input_len */
>         movq    %rbp, %r8               /* output target address */
> -       movl    $z_output_len, %r9d     /* decompressed length, end of relocs */
> +       movl    output_len(%rip), %r9d  /* decompressed length, end of relocs */
>         call    extract_kernel          /* returns kernel location in %rax */
>         popq    %rsi
>
> diff --git a/arch/x86/boot/compressed/mkpiggy.c b/arch/x86/boot/compressed/mkpiggy.c
> index 7e01248765b2..52aa56cdbacc 100644
> --- a/arch/x86/boot/compressed/mkpiggy.c
> +++ b/arch/x86/boot/compressed/mkpiggy.c
> @@ -60,6 +60,12 @@ int main(int argc, char *argv[])
>         printf(".incbin \"%s\"\n", argv[1]);
>         printf("input_data_end:\n");
>
> +       printf(".section \".rodata\",\"a\",@progbits\n");
> +       printf(".globl input_len\n");
> +       printf("input_len:\n\t.long %lu\n", ilen);
> +       printf(".globl output_len\n");
> +       printf("output_len:\n\t.long %lu\n", (unsigned long)olen);
> +
>         retval = 0;
>  bail:
>         if (f)
> --
> 2.26.2
>

  reply	other threads:[~2020-07-15  8:58 UTC|newest]

Thread overview: 113+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-29 14:09 [PATCH v3 0/7] x86/boot: Remove runtime relocations from compressed kernel Arvind Sankar
2020-06-29 14:09 ` [PATCH v3 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-06-29 15:48   ` Kees Cook
2020-06-29 15:50     ` Arvind Sankar
2020-06-29 15:51       ` Ard Biesheuvel
2020-06-29 16:10         ` Kees Cook
2020-06-29 14:09 ` [PATCH v3 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-06-29 15:50   ` Kees Cook
2020-07-14  9:20   ` Sedat Dilek
2020-07-14  9:47     ` Ard Biesheuvel
2020-06-29 14:09 ` [PATCH v3 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-06-29 15:53   ` Kees Cook
2020-06-29 14:09 ` [PATCH v3 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-06-29 15:55   ` Kees Cook
2020-06-29 14:09 ` [PATCH v3 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-06-29 16:04   ` Kees Cook
2020-06-29 17:01     ` Arvind Sankar
2020-07-14 13:20   ` Sedat Dilek
2020-06-29 14:09 ` [PATCH v3 6/7] x86/boot: Remove runtime relocations from head_{32,64}.S Arvind Sankar
2020-06-29 16:06   ` Kees Cook
2020-06-29 16:52     ` Arvind Sankar
2020-06-29 14:09 ` [PATCH v3 7/7] x86/boot: Check that there are no runtime relocations Arvind Sankar
2020-06-29 16:09   ` Kees Cook
2020-06-29 16:11     ` Ard Biesheuvel
2020-06-29 16:20       ` Kees Cook
2020-06-29 16:56         ` Arvind Sankar
2020-06-29 17:37           ` Fangrui Song
2020-06-29 18:11             ` Ard Biesheuvel
2020-06-29 23:34               ` Fangrui Song
2020-06-30 16:26                 ` Ard Biesheuvel
2020-06-30 17:54                   ` Arvind Sankar
2020-06-30 22:00                     ` Fangrui Song
2020-06-30 23:27                       ` Arvind Sankar
2020-07-01  6:44                         ` Ard Biesheuvel
2020-07-01 14:42                           ` Arvind Sankar
2020-06-29 18:43         ` Arvind Sankar
2020-07-14  2:38 ` [PATCH v4 0/7] x86/boot: Remove runtime relocations from compressed kernel Arvind Sankar
2020-07-14 13:15   ` Sedat Dilek
2020-07-14 14:15     ` Arvind Sankar
2020-07-14 18:13       ` Sedat Dilek
2020-07-14 18:30         ` Sedat Dilek
2020-07-14 18:33           ` Sedat Dilek
2020-07-14 19:21             ` Sedat Dilek
2020-07-14 19:29           ` Arvind Sankar
2020-07-14 19:53             ` Sedat Dilek
2020-07-14 20:07               ` Arvind Sankar
2020-07-14 20:10                 ` Sedat Dilek
2020-07-14 20:14                   ` Arvind Sankar
2020-07-14 20:17                     ` Sedat Dilek
2020-07-14 20:08               ` Sedat Dilek
2020-07-14 20:21                 ` Arvind Sankar
2020-07-14 20:24                   ` Sedat Dilek
2020-07-14 20:27                     ` Sedat Dilek
2020-07-14 20:35                       ` Arvind Sankar
2020-07-14 20:43                         ` Sedat Dilek
2020-07-14 21:07                           ` Arvind Sankar
2020-07-14 20:33                     ` Arvind Sankar
2020-07-15  0:41   ` [PATCH v5 0/7] x86/boot: Remove run-time " Arvind Sankar
2020-07-15  1:46     ` Sedat Dilek
2020-07-15  7:11       ` Sedat Dilek
2020-07-17 13:46     ` Arvind Sankar
2020-07-17 18:16       ` Nick Desaulniers
2020-07-17 18:21         ` Sedat Dilek
2020-07-17 20:17         ` [PATCH-next " Arvind Sankar
2020-07-17 23:46           ` Nick Desaulniers
2020-07-29 22:04           ` Kees Cook
2020-07-29 22:23             ` Arvind Sankar
2020-07-30  2:38               ` Kees Cook
2020-07-17 20:17         ` [PATCH-next v5 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-07-17 20:17         ` [PATCH-next v5 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-07-17 20:17         ` [PATCH-next v5 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-07-17 20:17         ` [PATCH-next v5 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-07-17 20:17         ` [PATCH-next v5 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-07-17 20:18         ` [PATCH-next v5 6/7] x86/boot: Remove run-time relocations from head_{32,64}.S Arvind Sankar
2020-07-17 20:18         ` [PATCH-next v5 7/7] x86/boot: Check that there are no run-time relocations Arvind Sankar
2020-07-18  5:44         ` [PATCH v5 0/7] x86/boot: Remove run-time relocations from compressed kernel Ard Biesheuvel
2020-07-18  7:01           ` Sedat Dilek
2020-07-24 23:25           ` Kees Cook
2020-07-31 14:53             ` Arvind Sankar
2020-07-31 14:58               ` Sedat Dilek
2020-07-31 20:27                 ` [PATCH v6 " Arvind Sankar
2020-07-31 20:27                   ` [PATCH v6 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-07-31 20:27                   ` [PATCH v6 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-07-31 20:27                   ` [PATCH v6 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-07-31 20:27                   ` [PATCH v6 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-07-31 20:27                   ` [PATCH v6 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-07-31 20:27                   ` [PATCH v6 6/7] x86/boot: Remove run-time relocations from head_{32,64}.S Arvind Sankar
2020-07-31 20:27                   ` [PATCH v6 7/7] x86/boot: Check that there are no run-time relocations Arvind Sankar
2020-07-31 23:15                   ` [PATCH v6 0/7] x86/boot: Remove run-time relocations from compressed kernel Kees Cook
2020-07-15  0:41   ` [PATCH v5 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-07-15  8:52     ` Sedat Dilek
2020-07-15  0:41   ` [PATCH v5 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-07-15  8:54     ` Sedat Dilek
2020-07-15  0:41   ` [PATCH v5 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-07-15  8:54     ` Sedat Dilek
2020-07-15  0:41   ` [PATCH v5 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-07-15  8:55     ` Sedat Dilek
2020-07-15  0:41   ` [PATCH v5 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-07-15  8:56     ` Sedat Dilek
2020-07-15  0:41   ` [PATCH v5 6/7] x86/boot: Remove run-time relocations from head_{32,64}.S Arvind Sankar
2020-07-15  8:58     ` Sedat Dilek [this message]
2020-07-15  9:03       ` Ard Biesheuvel
2020-07-15  9:10         ` Sedat Dilek
2020-07-15  0:41   ` [PATCH v5 7/7] x86/boot: Check that there are no run-time relocations Arvind Sankar
2020-07-15  9:00     ` Sedat Dilek
2020-07-15  9:12       ` Sedat Dilek
2020-07-14  2:38 ` [PATCH v4 1/7] x86/boot/compressed: Move .got.plt entries out of the .got section Arvind Sankar
2020-07-14  2:38 ` [PATCH v4 2/7] x86/boot/compressed: Force hidden visibility for all symbol references Arvind Sankar
2020-07-14  2:38 ` [PATCH v4 3/7] x86/boot/compressed: Get rid of GOT fixup code Arvind Sankar
2020-07-14  2:38 ` [PATCH v4 4/7] x86/boot: Add .text.* to setup.ld Arvind Sankar
2020-07-14  2:38 ` [PATCH v4 5/7] x86/boot: Remove run-time relocations from .head.text code Arvind Sankar
2020-07-14  2:38 ` [PATCH v4 6/7] x86/boot: Remove runtime relocations from head_{32,64}.S Arvind Sankar
2020-07-14  2:38 ` [PATCH v4 7/7] x86/boot: Check that there are no runtime relocations Arvind Sankar

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