[PATCH v9 3/6] module: use relative references for __ksymtab entries
From: Will Deacon <hidden>
Date: 2018-06-27 15:13:05
Also in:
linuxppc-dev, lkml
Hi Ard, On Tue, Jun 26, 2018 at 08:27:58PM +0200, Ard Biesheuvel wrote:
An ordinary arm64 defconfig build has ~64 KB worth of __ksymtab entries, each consisting of two 64-bit fields containing absolute references, to the symbol itself and to a char array containing its name, respectively.
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quoted hunk ↗ jump to hunk
diff --git a/include/linux/export.h b/include/linux/export.h index ea7df303d68d..ae072bc5aacf 100644 --- a/include/linux/export.h +++ b/include/linux/export.h@@ -18,12 +18,6 @@ #define VMLINUX_SYMBOL_STR(x) __VMLINUX_SYMBOL_STR(x) #ifndef __ASSEMBLY__ -struct kernel_symbol -{ - unsigned long value; - const char *name; -}; - #ifdef MODULE extern struct module __this_module; #define THIS_MODULE (&__this_module)@@ -54,17 +48,47 @@ extern struct module __this_module; #define __CRC_SYMBOL(sym, sec) #endif +#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS +#include <linux/compiler.h> +/* + * Emit the ksymtab entry as a pair of relative references: this reduces + * the size by half on 64-bit architectures, and eliminates the need for + * absolute relocations that require runtime processing on relocatable + * kernels. + */ +#define __KSYMTAB_ENTRY(sym, sec) \ + __ADDRESSABLE(sym) \ + asm(" .section \"___ksymtab" sec "+" #sym "\", \"a\" \n" \ + " .balign 8 \n" \
Can we use KSYM_ALIGN here instead of 8, or do we need the 8-byte alignment even on 32-bit architectures? Will