From 4e918ab13eaf40f19938659cb5a22c93172778a8 Mon Sep 17 00:00:00 2001 From: Ard Biesheuvel Date: Fri, 26 Nov 2021 19:37:27 +0100 Subject: ARM: assembler: add optimized ldr/str macros to load variables from memory We will be adding variable loads to various hot paths, so it makes sense to add a helper macro that can load variables from asm code without the use of literal pool entries. On v7 or later, we can simply use MOVW/MOVT pairs, but on earlier cores, this requires a bit of hackery to emit a instruction sequence that implements this using a sequence of ADD/LDR instructions. Acked-by: Linus Walleij Acked-by: Nicolas Pitre Signed-off-by: Ard Biesheuvel Tested-by: Marc Zyngier Tested-by: Vladimir Murzin # ARMv7M --- arch/arm/include/asm/assembler.h | 45 ++++++++++++++++++++++++++++++++++++---- 1 file changed, 41 insertions(+), 4 deletions(-) (limited to 'arch/arm/include/asm') diff --git a/arch/arm/include/asm/assembler.h b/arch/arm/include/asm/assembler.h index 1b9d4df331aa..2095638b7140 100644 --- a/arch/arm/include/asm/assembler.h +++ b/arch/arm/include/asm/assembler.h @@ -568,12 +568,12 @@ THUMB( orr \reg , \reg , #PSR_T_BIT ) /* * mov_l - move a constant value or [relocated] address into a register */ - .macro mov_l, dst:req, imm:req + .macro mov_l, dst:req, imm:req, cond .if __LINUX_ARM_ARCH__ < 7 - ldr \dst, =\imm + ldr\cond \dst, =\imm .else - movw \dst, #:lower16:\imm - movt \dst, #:upper16:\imm + movw\cond \dst, #:lower16:\imm + movt\cond \dst, #:upper16:\imm .endif .endm @@ -611,6 +611,43 @@ THUMB( orr \reg , \reg , #PSR_T_BIT ) __adldst_l str, \src, \sym, \tmp, \cond .endm + .macro __ldst_va, op, reg, tmp, sym, cond +#if __LINUX_ARM_ARCH__ >= 7 || \ + (defined(MODULE) && defined(CONFIG_ARM_MODULE_PLTS)) || \ + (defined(CONFIG_LD_IS_LLD) && CONFIG_LLD_VERSION < 140000) + mov_l \tmp, \sym, \cond + \op\cond \reg, [\tmp] +#else + /* + * Avoid a literal load, by emitting a sequence of ADD/LDR instructions + * with the appropriate relocations. The combined sequence has a range + * of -/+ 256 MiB, which should be sufficient for the core kernel and + * for modules loaded into the module region. + */ + .globl \sym + .reloc .L0_\@, R_ARM_ALU_PC_G0_NC, \sym + .reloc .L1_\@, R_ARM_ALU_PC_G1_NC, \sym + .reloc .L2_\@, R_ARM_LDR_PC_G2, \sym +.L0_\@: sub\cond \tmp, pc, #8 +.L1_\@: sub\cond \tmp, \tmp, #4 +.L2_\@: \op\cond \reg, [\tmp, #0] +#endif + .endm + + /* + * ldr_va - load a 32-bit word from the virtual address of \sym + */ + .macro ldr_va, rd:req, sym:req, cond + __ldst_va ldr, \rd, \rd, \sym, \cond + .endm + + /* + * str_va - store a 32-bit word to the virtual address of \sym + */ + .macro str_va, rn:req, sym:req, tmp:req, cond + __ldst_va str, \rn, \tmp, \sym, \cond + .endm + /* * rev_l - byte-swap a 32-bit value * -- cgit