From ced79d864bfd70ad80699f362938d45526034378 Mon Sep 17 00:00:00 2001 From: Josh Poimboeuf Date: Fri, 6 May 2022 14:14:32 +0200 Subject: x86/mm: Simplify RESERVE_BRK() commit a1e2c031ec3949b8c039b739c0b5bf9c30007b00 upstream. RESERVE_BRK() reserves data in the .brk_reservation section. The data is initialized to zero, like BSS, so the macro specifies 'nobits' to prevent the data from taking up space in the vmlinux binary. The only way to get the compiler to do that (without putting the variable in .bss proper) is to use inline asm. The macro also has a hack which encloses the inline asm in a discarded function, which allows the size to be passed (global inline asm doesn't allow inputs). Remove the need for the discarded function hack by just stringifying the size rather than supplying it as an input to the inline asm. Signed-off-by: Josh Poimboeuf Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Reviewed-by: Borislav Petkov Link: https://lore.kernel.org/r/20220506121631.133110232@infradead.org [nathan: Fix conflict due to lack of 2b6ff7dea670 and 33def8498fdd] Signed-off-by: Nathan Chancellor Signed-off-by: Greg Kroah-Hartman --- arch/x86/include/asm/setup.h | 30 +++++++++++------------------- 1 file changed, 11 insertions(+), 19 deletions(-) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/setup.h b/arch/x86/include/asm/setup.h index ed8ec011a9fd..58cfd5bd209a 100644 --- a/arch/x86/include/asm/setup.h +++ b/arch/x86/include/asm/setup.h @@ -94,27 +94,19 @@ 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. Must be - * used at file scope. + * Reserve space in the brk section. The name must be unique within the file, + * and somewhat descriptive. The size is in bytes. * - * (This uses a temp function to wrap the asm so we can pass it the - * size parameter; otherwise we wouldn't be able to. We can't use a - * "section" attribute on a normal variable because it always ends up - * being @progbits, which ends up allocating space in the vmlinux - * executable.) + * 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,sz) \ - static void __section(.discard.text) __used notrace \ - __brk_reservation_fn_##name##__(void) { \ - asm volatile ( \ - ".pushsection .brk_reservation,\"aw\",@nobits;" \ - ".brk." #name ":" \ - " 1:.skip %c0;" \ - " .size .brk." #name ", . - 1b;" \ - " .popsection" \ - : : "i" (sz)); \ - } +#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") /* Helper for reserving space for arrays of things */ #define RESERVE_BRK_ARRAY(type, name, entries) \ -- cgit v1.2.3