4.19-stable review patch. If anyone has any objections, please let me know.
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From: Josh Poimboeuf jpoimboe@kernel.org
commit e32683c6f7d22ba624e0bfc58b02cf3348bdca63 upstream.
With binutils 2.26, RESERVE_BRK() causes a build failure:
/tmp/ccnGOKZ5.s: Assembler messages: /tmp/ccnGOKZ5.s:98: Error: missing ')' /tmp/ccnGOKZ5.s:98: Error: missing ')' /tmp/ccnGOKZ5.s:98: Error: missing ')' /tmp/ccnGOKZ5.s:98: Error: junk at end of line, first unrecognized character is `U'
The problem is this line:
RESERVE_BRK(early_pgt_alloc, INIT_PGT_BUF_SIZE)
Specifically, the INIT_PGT_BUF_SIZE macro which (via PAGE_SIZE's use _AC()) has a "1UL", which makes older versions of the assembler unhappy. Unfortunately the _AC() macro doesn't work for inline asm.
Inline asm was only needed here to convince the toolchain to add the STT_NOBITS flag. However, if a C variable is placed in a section whose name is prefixed with ".bss", GCC and Clang automatically set STT_NOBITS. In fact, ".bss..page_aligned" already relies on this trick.
So fix the build failure (and simplify the macro) by allocating the variable in C.
Also, add NOLOAD to the ".brk" output section clause in the linker script. This is a failsafe in case the ".bss" prefix magic trick ever stops working somehow. If there's a section type mismatch, the GNU linker will force the ".brk" output section to be STT_NOBITS. The LLVM linker will fail with a "section type mismatch" error.
Note this also changes the name of the variable from .brk.##name to __brk_##name. The variable names aren't actually used anywhere, so it's harmless.
Fixes: a1e2c031ec39 ("x86/mm: Simplify RESERVE_BRK()") Reported-by: Joe Damato jdamato@fastly.com Reported-by: Byungchul Park byungchul.park@lge.com Signed-off-by: Josh Poimboeuf jpoimboe@kernel.org Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Tested-by: Joe Damato jdamato@fastly.com Link: https://lore.kernel.org/r/22d07a44c80d8e8e1e82b9a806ddc8c6bbb2606e.165475903... [nathan: Fix conflict due to lack of 360db4ace311 and resolve silent conflict with 360db4ace3117] Signed-off-by: Nathan Chancellor nathan@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/x86/include/asm/setup.h | 38 +++++++++++++++++++++----------------- arch/x86/kernel/vmlinux.lds.S | 4 ++-- 2 files changed, 23 insertions(+), 19 deletions(-)
--- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -91,19 +91,16 @@ 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, - * and somewhat descriptive. The size is in bytes. + * Reserve space in the .brk section, which is a block of memory from which the + * caller is allowed to allocate very early (before even memblock is available) + * by calling extend_brk(). All allocated memory will be eventually converted + * to memblock. Any leftover unallocated memory will be freed. * - * 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. + * The size is in bytes. */ -#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") +#define RESERVE_BRK(name, size) \ + __section(.bss..brk) __aligned(1) __used \ + static char __brk_##name[size]
/* Helper for reserving space for arrays of things */ #define RESERVE_BRK_ARRAY(type, name, entries) \ @@ -121,12 +118,19 @@ asmlinkage void __init x86_64_start_rese
#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 */ + +.macro __RESERVE_BRK name, size + .pushsection .bss..brk, "aw" +GLOBAL(__brk_\name) + .skip \size +END(__brk_\name) .popsection +.endm + +#define RESERVE_BRK(name, size) __RESERVE_BRK name, size + #endif /* __ASSEMBLY__ */ + #endif /* _ASM_X86_SETUP_H */ --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -380,10 +380,10 @@ SECTIONS }
. = 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 */ + *(.bss..brk) /* areas brk users have reserved */ __brk_limit = .; }