Messages in this thread | | | From | Joe Damato <> | Date | Wed, 8 Jun 2022 12:10:04 +0300 | Subject | Re: 5.19-rc1 x86 build failure |
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On Tue, Jun 07, 2022 at 05:59:56PM -0700, Josh Poimboeuf wrote: > On Tue, Jun 07, 2022 at 12:42:33PM +0000, Andrew Cooper wrote: > > On 07/06/2022 13:19, Joe Damato wrote: > > > 96 .pushsection .brk_reservation,"aw",@nobits > > > 97 .brk.early_pgt_alloc: > > > 98 ???? 00000000 .skip ((2 * 3) * ((1UL) << 12)) > > > **** Error: missing ')' > > > **** Error: missing ')' > > > **** Error: missing ')' > > > **** Error: junk at end of line, first unrecognized character is `U' > > > 98 0000 > > > 100 .popsection > > > > > > This comes from arch/x86/mm/init.c, which has the following code: > > > > > > RESERVE_BRK(early_pgt_alloc, INIT_PGT_BUF_SIZE); > > > > > > wherein INIT_PGT_BUF_SIZE (via PAGE_SIZE) has a "1UL" which makes the > > > assembler unhappy. > > > > > > I don't really know what the correct way to fix this is; it seems that the > > > macro _AC should handle this if ASSEMBLY is defined, IIUC, but that does > > > not seem to be the case at this point in init.c. > > > > > > Perhaps I am doing something incorrect during the build process causing > > > this to happen? > > > > The problem is that _AC() is evaluated in C context (so gains the UL/ULL > > suffix), and the C'd string is fed directly into the assembler (where > > older binutils doesn't tolerate the suffix). > > > > Short of having a _PAGE_SIZE which is an explicitly non-AC()'d constant, > > I'm not sure what to suggest. Ideally, you'd want to temporarily define > > __ASSEMBLY__ around the expansion of __stringify(), but I don't think > > that's possible as RESERVE_BRK() is a macro itself. > > Joe, what version of binutils do you have?
I am using binutils: 2.26.1-1ubuntu1~16.04.8+esm4.
> We can fix this by taking a completely different approach: define the > variable in C and just do the "nobits" in the linker script, like below. > I can work up a proper patch tomorrow.
The change below makes sense to me. I applied it locally and was able to build the kernel again.
Let me know if you'd like me to try building the next patch you write up. > diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h > index 7590ac2570b9..4704184a2d78 100644 > --- a/arch/x86/include/asm/setup.h > +++ b/arch/x86/include/asm/setup.h > @@ -108,19 +108,11 @@ extern unsigned long _brk_end; > void *extend_brk(size_t size, size_t align); > > /* > - * Reserve space in the brk section. The name must be unique within the file, > + * Reserve space in the .brk section. The name must be unique within vmlinux, > * and somewhat descriptive. The size is in bytes. > - * > - * The allocation is done using inline asm (rather than using a section > - * attribute on a normal variable) in order to allow the use of @nobits, so > - * that it doesn't take up any space in the vmlinux file. > */ > #define RESERVE_BRK(name, size) \ > - asm(".pushsection .brk_reservation,\"aw\",@nobits\n\t" \ > - ".brk." #name ":\n\t" \ > - ".skip " __stringify(size) "\n\t" \ > - ".size .brk." #name ", " __stringify(size) "\n\t" \ > - ".popsection\n\t") > + char __brk_##name[size] __section(".brk_reservation"); > > extern void probe_roms(void); > #ifdef __i386__ > @@ -133,12 +125,16 @@ asmlinkage void __init x86_64_start_reservations(char *real_mode_data); > > #endif /* __i386__ */ > #endif /* _SETUP */ > -#else > -#define RESERVE_BRK(name,sz) \ > - .pushsection .brk_reservation,"aw",@nobits; \ > -.brk.name: \ > -1: .skip sz; \ > - .size .brk.name,.-1b; \ > + > +#else /* __ASSEMBLY */ > + > +#define RESERVE_BRK(name, size) \ > + .pushsection .brk_reservation, "aw"; \ > +__brk_##name: \ > +1: .skip size; \ > + .size __brk_##name, . - 1b; \ > .popsection > + > #endif /* __ASSEMBLY__ */ > + > #endif /* _ASM_X86_SETUP_H */ > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > index 91831b9d8aa8..f105b8aa055e 100644 > --- a/arch/x86/kernel/vmlinux.lds.S > +++ b/arch/x86/kernel/vmlinux.lds.S > @@ -392,7 +392,7 @@ SECTIONS > __end_of_kernel_reserve = .; > > . = ALIGN(PAGE_SIZE); > - .brk : AT(ADDR(.brk) - LOAD_OFFSET) { > + .brk (NOLOAD) : AT(ADDR(.brk) - LOAD_OFFSET) { > __brk_base = .; > . += 64 * 1024; /* 64k alignment slop space */ > *(.brk_reservation) /* areas brk users have reserved */
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