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From: Borislav Petkov <bp@alien8.de>
To: Nick Desaulniers <ndesaulniers@google.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
	Jarkko Sakkinen <jarkko.sakkinen@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>,
	clang-built-linux <clang-built-linux@googlegroups.com>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<x86@kernel.org>, Tri Vo <trong@android.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Rob Herring <robh@kernel.org>,
	George Rimar <grimar@accesssoftek.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Fangrui Song <maskray@google.com>,
	Peter Smith <Peter.Smith@arm.com>, Rui Ueyama <ruiu@google.com>
Subject: Re: [PATCH v2] x86, realmode: explicitly set entry via command line
Date: Wed, 25 Sep 2019 19:10:25 +0200	[thread overview]
Message-ID: <20190925171025.GF3891@zn.tnic> (raw)
In-Reply-To: <CAKwvOdneE7kMupFzxZC-6c=ps_98FP+Nz88fCXQ74z90hmaaXQ@mail.gmail.com>

On Wed, Sep 25, 2019 at 09:35:24AM -0700, Nick Desaulniers wrote:
> Thanks for the consideration Boris.  So IIUC if the preceding sections
> are larger than 0x1000 altogether, setting the entry there will be
> wrong?

Well, I spent some time this morning grepping to find out whether PA
0x1000 was magical but didn't find anything. Perhaps hpa can refresh my
memory...

> Currently, .text looks like it's currently at 0x1000 for a defconfig,
> and I assume that could move in the case I stated above?

Yes, I think we shouldn't hardcode.

> $ readelf -S arch/x86/realmode/rm/realmode.elf | grep text
>   [ 3] .text             PROGBITS        00001000 201000 000f51 00  AX
>  0   0 4096
> ...
> 
> In that case, it seems that maybe I should set the ENTRY in the linker
> script as:
> diff --git a/arch/x86/realmode/rm/realmode.lds.S
> b/arch/x86/realmode/rm/realmode.lds.S
> index 3bb980800c58..64d135d1ee63 100644
> --- a/arch/x86/realmode/rm/realmode.lds.S
> +++ b/arch/x86/realmode/rm/realmode.lds.S
> @@ -11,6 +11,7 @@
> 
>  OUTPUT_FORMAT("elf32-i386")
>  OUTPUT_ARCH(i386)
> +ENTRY(pa_text_start)

Well, looking at arch/x86/boot/setup.ld, it does do:

ENTRY(_start)

for the global _start symbol in .../boot/header.S.

So you doing the respective thing in that linker script would make
sense...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

  parent reply	other threads:[~2019-09-25 17:10 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-23 22:24 [PATCH] x86, realmode: explicitly set ENTRY in linker script Nick Desaulniers
2019-09-24 17:30 ` Sedat Dilek
2019-09-24 18:24 ` Nathan Chancellor
2019-09-24 18:32   ` Nick Desaulniers
2019-09-24 19:33     ` [PATCH v2] x86, realmode: explicitly set entry via command line Nick Desaulniers
2019-09-24 19:37       ` Nick Desaulniers
2019-09-25 10:20       ` Borislav Petkov
2019-09-25 16:35         ` Nick Desaulniers
2019-09-25 17:02           ` Peter Smith
2019-09-25 17:10           ` Borislav Petkov [this message]
2019-09-25 18:09             ` [PATCH v3] x86, realmode: explicitly set entry via ENTRY in linker script Nick Desaulniers
2019-10-01 10:37               ` [tip: x86/boot] x86/realmode: Explicitly set entry point " tip-bot2 for Nick Desaulniers
2019-10-01 20:18               ` tip-bot2 for Nick Desaulniers

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