On Mon, 20 Nov 2023, Andrew Cooper wrote: > GCC complains: > > In file included from arch/arm/efi/boot.c:700: > arch/arm/efi/efi-boot.h: In function 'efi_arch_handle_cmdline': > arch/arm/efi/efi-boot.h:482:16: error: assignment discards 'const' > qualifier from pointer target type [-Werror=discarded-qualifiers] > 482 | name.s = "xen"; > | ^ > > There's no easy option. .rodata is really read-only, so the fact Xen doesn't > crash means these strings aren't written to. > > Lie to the compiler using a union. > > Signed-off-by: Andrew Cooper <[email protected]> > --- > CC: Jan Beulich <[email protected]> > CC: Roger Pau Monné <[email protected]> > CC: Wei Liu <[email protected]> > CC: Stefano Stabellini <[email protected]> > CC: Julien Grall <[email protected]> > CC: Volodymyr Babchuk <[email protected]> > CC: Bertrand Marquis <[email protected]> > CC: Michal Orzel <[email protected]> > CC: Roberto Bagnara <[email protected]> > CC: Nicola Vetrini <[email protected]> > > I *really* don't like this, but it's the only suggestion given.
Hi Andrew, I am trying to understand what is the part you don't like. I understand that union string looks iffy due to being a union with const and non-const. Is that your concern or you also spotted additional problems with this? If that is the only issue, maybe we can come up with a matter in-code comment or commit message. (The TODO is not immediately obvious to me what the issue to be improved is.) > --- > xen/arch/arm/efi/efi-boot.h | 2 +- > xen/arch/x86/efi/efi-boot.h | 3 ++- > 2 files changed, 3 insertions(+), 2 deletions(-) > > diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h > index 1c3640bb65fd..c26bf18b68b9 100644 > --- a/xen/arch/arm/efi/efi-boot.h > +++ b/xen/arch/arm/efi/efi-boot.h > @@ -479,7 +479,7 @@ static void __init efi_arch_handle_cmdline(CHAR16 > *image_name, > w2s(&name); > } > else > - name.s = "xen"; > + name.cs = "xen"; /* TODO, find a better way of doing this. */ > > prop_len = 0; > prop_len += snprintf(buf + prop_len, > diff --git a/xen/arch/x86/efi/efi-boot.h b/xen/arch/x86/efi/efi-boot.h > index eebc54180bf7..e2d256e0517b 100644 > --- a/xen/arch/x86/efi/efi-boot.h > +++ b/xen/arch/x86/efi/efi-boot.h > @@ -324,7 +324,8 @@ static void __init efi_arch_handle_cmdline(CHAR16 > *image_name, > w2s(&name); > } > else > - name.s = "xen"; > + name.cs = "xen"; /* TODO, find a better way of doing this. */ > + > place_string(&mbi.cmdline, name.s); > > if ( mbi.cmdline ) > -- > 2.30.2 > >
