Re: [PATCH -next v4 2/2] x86/boot/compressed: Add "-Wall" flag to Makefile

From: Borislav Petkov <bp@alien8.de>
To: Li Zetao <lizetao1@huawei.com>
Cc: keescook@chromium.org, tglx@linutronix.de, mingo@redhat.com,
	dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
	kirill.shutemov@linux.intel.com, tony.luck@intel.com,
	masahiroy@kernel.org, michael.roth@amd.com,
	sathyanarayanan.kuppuswamy@linux.intel.com, nathan@kernel.org,
	ndesaulniers@google.com, brijesh.singh@amd.com,
	peterz@infradead.org, venu.busireddy@oracle.com,
	linux-kernel@vger.kernel.org, akpm@linux-foundation.org
Subject: Re: [PATCH -next v4 2/2] x86/boot/compressed: Add "-Wall" flag to Makefile
Date: Mon, 17 Oct 2022 19:01:40 +0200	[thread overview]
Message-ID: <Y02KdJfTSFRlbnwn@zn.tnic> (raw)
In-Reply-To: <20221011012904.2330473-3-lizetao1@huawei.com>

On Tue, Oct 11, 2022 at 01:29:04AM +0000, Li Zetao wrote:
> This warning is disabled in the main Makefile for this reason so we

Who's "we"?

Please use passive voice in your commit message: no "we" or "I", etc,
and describe your changes in imperative mood.

Also, pls read section "2) Describe your changes" in
Documentation/process/submitting-patches.rst for more details.

Also, see section "Changelog" in
Documentation/process/maintainer-tip.rst

Bottom line is: personal pronouns are ambiguous in text, especially with
so many parties/companies/etc developing the kernel so let's avoid them
please.

In any case, it is getting there but this is not how you structure a
patchset like this. The proper order is:

1st patch: Remove unused variables

2nd patch: Fix -Wframe-address warning and explain why

3rd patch: Fix arch/x86/boot/compressed/acpi.c:23:1: warning: unused function "__efi_get_rsdp_addr" [-Wunused-function]

Btw, I also get with -Wall

In function ‘find_trampoline_placement’,
    inlined from ‘paging_prepare’ at arch/x86/boot/compressed/pgtable_64.c:135:35:
arch/x86/boot/compressed/pgtable_64.c:60:30: warning: array subscript 0 is outside array bounds of ‘short unsigned int[0]’ [-Warray-bounds]
   60 |                 ebda_start = *(unsigned short *)0x40e << 4;
      |                              ^~~~~~~~~~~~~~~~~~~~~~~~
arch/x86/boot/compressed/pgtable_64.c:61:30: warning: array subscript 0 is outside array bounds of ‘short unsigned int[0]’ [-Warray-bounds]
   61 |                 bios_start = *(unsigned short *)0x413 << 10;
      |                              ^~~~~~~~~~~~~~~~~~~~~~~~
In function ‘bios_get_rsdp_addr’,
    inlined from ‘get_rsdp_addr’ at arch/x86/boot/compressed/acpi.c:163:8:
arch/x86/boot/compressed/acpi.c:130:19: warning: array subscript 0 is outside array bounds of ‘u16[0]’ {aka ‘short unsigned int[]’} [-Warray-bounds]
  130 |         address = *(u16 *)ACPI_EBDA_PTR_LOCATION;

That should be a separate patch too.

Nth patch(es): Fix more warnings after building at least

	"allnoconfig" "defconfig" "allmodconfig" "allyesconfig"

for both 32-bit and 64-bit. A bunch of randconfigs on a big machine
would help a lot.

N + kth patch: Add -std=gnu11

X. Final patch: Add -Wall to compressed/Makefile.

In that order so that no warnings are seen when doing random builds.

Thx.

-- 
Regards/Gruss,
    Boris.

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