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arm64: alternative: patch alternatives in the vDSO

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

Signed-off-by: Joey 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: Mark Rutland <mark.rutland@arm.com>
Link: https://lore.kernel.org/r/20220830104833.34636-3-joey.gouly@arm.com
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
This commit is contained in:
Joey Gouly 2022-08-30 11:48:32 +01:00 committed by Catalin Marinas
parent b3adc3844e
commit 4e3bca8f7c
4 changed files with 38 additions and 3 deletions
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3
arch/arm64/include/asm/vdso.h
View File

@ -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 */

28
arch/arm64/kernel/alternative.c
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@ -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);
}

3
arch/arm64/kernel/vdso.c
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@ -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,

7
arch/arm64/kernel/vdso/vdso.lds.S
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@ -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*) }