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From:   Zhenzhong Duan <zhenzhong.duan@gmail.com>
Date:   Mon, 13 Jan 2020 10:43:14 +0800
Message-ID: <CAFH1YnN8v+8UH3RvaeT7TJEdtEyxhoBA-ZEMk-mRFWNad8e9Jw@mail.gmail.com>
Subject: Re: [PATCH v2] x86/boot/KASLR: Fix unused variable warning
To:     Borislav Petkov <bp@alien8.de>
Cc:     Arvind Sankar <nivedita@alum.mit.edu>,
        linux-kernel@vger.kernel.org, x86@kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
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On Fri, Jan 10, 2020 at 5:00 PM Borislav Petkov <bp@alien8.de> wrote:
>
> On Fri, Jan 10, 2020 at 10:27:02AM +0800, Zhenzhong Duan wrote:
> > Yes. Will you send this formally?
>
> And then a flood of fix-this-trivial-warning patches ensues?
>
> You should know that they have the lowest prio when it comes to looking
> at them.
I see.
Just tried Arvind's patch, result is not that bad. Below are all
warnings during build:
In fact, only gop.c and kaslr.c have compile warning.

/root/kernel/drivers/firmware/efi/libstub/gop.c: In function =E2=80=98efi_s=
etup_gop=E2=80=99:
/root/kernel/drivers/firmware/efi/libstub/gop.c:174:18: warning:
=E2=80=98pixel_format=E2=80=99 may be used uninitialized in this function
[-Wmaybe-uninitialized]
  setup_pixel_info(si, pixels_per_scan_line, pixel_info, pixel_format);
                  ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:97:6: note:
=E2=80=98pixel_format=E2=80=99 was declared here
  int pixel_format;
      ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:166:45: warning:
=E2=80=98fb_base=E2=80=99 may be used uninitialized in this function
[-Wmaybe-uninitialized]
  ext_lfb_base =3D (u64)(unsigned long)fb_base >> 32;
                                             ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:95:6: note: =E2=80=98fb_bas=
e=E2=80=99
was declared here
  u64 fb_base;
      ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:174:18: warning:
=E2=80=98pixels_per_scan_line=E2=80=99 may be used uninitialized in this fu=
nction
[-Wmaybe-uninitialized]
  setup_pixel_info(si, pixels_per_scan_line, pixel_info, pixel_format);
                  ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:93:6: note:
=E2=80=98pixels_per_scan_line=E2=80=99 was declared here
  u32 pixels_per_scan_line;
      ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:163:17: warning:
=E2=80=98height=E2=80=99 may be used uninitialized in this function
[-Wmaybe-uninitialized]
  si->lfb_height =3D height;
                 ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:92:13: note: =E2=80=98heigh=
t=E2=80=99
was declared here
  u16 width, height;
             ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:162:16: warning:
=E2=80=98width=E2=80=99 may be used uninitialized in this function
[-Wmaybe-uninitialized]
  si->lfb_width =3D width;
                ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:92:6: note: =E2=80=98width=
=E2=80=99
was declared here
  u16 width, height;
      ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:271:18: warning:
=E2=80=98pixel_format=E2=80=99 may be used uninitialized in this function
[-Wmaybe-uninitialized]
  setup_pixel_info(si, pixels_per_scan_line, pixel_info, pixel_format);
                  ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:194:6: note:
=E2=80=98pixel_format=E2=80=99 was declared here
  int pixel_format;
      ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:263:45: warning:
=E2=80=98fb_base=E2=80=99 may be used uninitialized in this function
[-Wmaybe-uninitialized]
  ext_lfb_base =3D (u64)(unsigned long)fb_base >> 32;
                                             ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:192:6: note: =E2=80=98fb_ba=
se=E2=80=99
was declared here
  u64 fb_base;
      ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:271:18: warning:
=E2=80=98pixels_per_scan_line=E2=80=99 may be used uninitialized in this fu=
nction
[-Wmaybe-uninitialized]
  setup_pixel_info(si, pixels_per_scan_line, pixel_info, pixel_format);
                  ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:190:6: note:
=E2=80=98pixels_per_scan_line=E2=80=99 was declared here
  u32 pixels_per_scan_line;
      ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:260:17: warning:
=E2=80=98height=E2=80=99 may be used uninitialized in this function
[-Wmaybe-uninitialized]
  si->lfb_height =3D height;
                 ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:189:13: note: =E2=80=98heig=
ht=E2=80=99
was declared here
  u16 width, height;
             ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:259:16: warning:
=E2=80=98width=E2=80=99 may be used uninitialized in this function
[-Wmaybe-uninitialized]
  si->lfb_width =3D width;
                ^
/root/kernel/drivers/firmware/efi/libstub/gop.c:189:6: note: =E2=80=98width=
=E2=80=99
was declared here
  u16 width, height;

/root/kernel/arch/x86/boot/compressed/kaslr.c: In function =E2=80=98process=
_mem_region=E2=80=99:
/root/kernel/arch/x86/boot/compressed/kaslr.c:698:6: warning: unused
variable =E2=80=98i=E2=80=99 [-Wunused-variable]
  int i;

Regards
Zhenzhong