Commit 4e3bca8f authored by Joey Gouly's avatar Joey Gouly Committed by Catalin Marinas
Browse files

arm64: alternative: patch alternatives in the vDSO 



Make it possible to use alternatives in the vDSO, so that better
implementations can be used if possible.

Signed-off-by: default avatarJoey Gouly <joey.gouly@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Acked-by: default avatarMark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20220830104833.34636-3-joey.gouly@arm.com


Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
parent b3adc384

arch/arm64/include/asm/vdso.h

+3 −0
Original line number Diff line number Diff line
@@ -26,6 +26,9 @@ 
	(void *)(vdso_offset_##name - VDSO_LBASE + (unsigned long)(base)); \

})



extern char vdso_start[], vdso_end[];

extern char vdso32_start[], vdso32_end[];



#endif /* !__ASSEMBLY__ */



#endif /* __ASM_VDSO_H */

arch/arm64/kernel/alternative.c

+28 −0
Original line number Diff line number Diff line
@@ -10,11 +10,14 @@ 


#include <linux/init.h>

#include <linux/cpu.h>

#include <linux/elf.h>

#include <asm/cacheflush.h>

#include <asm/alternative.h>

#include <asm/cpufeature.h>

#include <asm/insn.h>

#include <asm/module.h>

#include <asm/sections.h>

#include <asm/vdso.h>

#include <linux/stop_machine.h>



#define __ALT_PTR(a, f)		((void *)&(a)->f + (a)->f)
@@ -192,6 +195,30 @@ static void __nocfi __apply_alternatives(struct alt_region *region, bool is_modu 
	}

}



void apply_alternatives_vdso(void)

{

	struct alt_region region;

	const struct elf64_hdr *hdr;

	const struct elf64_shdr *shdr;

	const struct elf64_shdr *alt;

	DECLARE_BITMAP(all_capabilities, ARM64_NPATCHABLE);



	bitmap_fill(all_capabilities, ARM64_NPATCHABLE);



	hdr = (struct elf64_hdr *)vdso_start;

	shdr = (void *)hdr + hdr->e_shoff;

	alt = find_section(hdr, shdr, ".altinstructions");

	if (!alt)

		return;



	region = (struct alt_region){

		.begin	= (void *)hdr + alt->sh_offset,

		.end	= (void *)hdr + alt->sh_offset + alt->sh_size,

	};



	__apply_alternatives(&region, false, &all_capabilities[0]);

}



/*

 * We might be patching the stop_machine state machine, so implement a

 * really simple polling protocol here.
@@ -225,6 +252,7 @@ static int __apply_alternatives_multi_stop(void *unused) 


void __init apply_alternatives_all(void)

{

	apply_alternatives_vdso();

	/* better not try code patching on a live SMP system */

	stop_machine(__apply_alternatives_multi_stop, NULL, cpu_online_mask);

}

arch/arm64/kernel/vdso.c

+0 −3
Original line number Diff line number Diff line
@@ -29,9 +29,6 @@ 
#include <asm/signal32.h>

#include <asm/vdso.h>



extern char vdso_start[], vdso_end[];

extern char vdso32_start[], vdso32_end[];



enum vdso_abi {

	VDSO_ABI_AA64,

	VDSO_ABI_AA32,

arch/arm64/kernel/vdso/vdso.lds.S

+7 −0
Original line number Diff line number Diff line
@@ -48,6 +48,13 @@ SECTIONS 
	PROVIDE (_etext = .);

	PROVIDE (etext = .);



	. = ALIGN(4);

	.altinstructions : {

		__alt_instructions = .;

		*(.altinstructions)

		__alt_instructions_end = .;

	}



	.dynamic	: { *(.dynamic) }		:text	:dynamic



	.rela.dyn	: ALIGN(8) { *(.rela .rela*) }