On 21/11/2023 6:03 pm, Andrew Cooper wrote: > On 21/11/2023 8:40 am, Jan Beulich wrote: >> On 20.11.2023 23:49, 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. >> And the consuming sites confirm this being the case. Hence ... >> >>> Lie to the compiler using a union. >> ... to at least slightly limit the lying, how about ... >> >>> --- 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, >> ... you also switch to using name.cs down below here and ... >> >>> --- 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); >> ... here? >> >> An alternative would be to introduce 'char xen[4] = "xen";' in both >> cases, and use them instead of plain string literals. > They'd have to be static, or dynamically allocated or they'll end up out > of scope, wont they? > > I have to admit I find this logic very hard to follow. > > Furthermore, I note: > > mbi.boot_loader_name = (long)"EFI"; > > which is exactly the kind of pointer which is liable to end up being > edited via kextra in the other patch.
Hang on. place_string()'ing here is just to prepend a piece of data we go to other lengths to strip and ignore later in boot. On x86 we can just delete it and make our lives simpler. I hope the same is true on ARM too. ~Andrew
