Commit-ID: 79e1932fa3cedd731ddbd6af111fe4db8ca109ae Gitweb: https://git.kernel.org/tip/79e1932fa3cedd731ddbd6af111fe4db8ca109ae Author: Chang S. Bae <chang.seok.bae@xxxxxxxxx> AuthorDate: Wed, 8 May 2019 03:02:26 -0700 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitDate: Sat, 22 Jun 2019 11:38:54 +0200 x86/entry/64: Introduce the FIND_PERCPU_BASE macro GSBASE is used to find per-CPU data in the kernel. But when GSBASE is unknown, the per-CPU base can be found from the per_cpu_offset table with a CPU NR. The CPU NR is extracted from the limit field of the CPUNODE entry in GDT, or by the RDPID instruction. This is a prerequisite for using FSGSBASE in the low level entry code. Also, add the GAS-compatible RDPID macro as binutils 2.21 do not support it. Support is added in version 2.27. [ tglx: Massaged changelog ] Suggested-by: H. Peter Anvin <hpa@xxxxxxxxx> Signed-off-by: Chang S. Bae <chang.seok.bae@xxxxxxxxx> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx> Cc: Ravi Shankar <ravi.v.shankar@xxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Link: https://lkml.kernel.org/r/1557309753-24073-12-git-send-email-chang.seok.bae@xxxxxxxxx --- arch/x86/entry/calling.h | 34 ++++++++++++++++++++++++++++++++++ arch/x86/include/asm/inst.h | 15 +++++++++++++++ 2 files changed, 49 insertions(+) diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index efb0d1b1f15f..9a524360ae2e 100644 --- a/arch/x86/entry/calling.h +++ b/arch/x86/entry/calling.h @@ -6,6 +6,7 @@ #include <asm/percpu.h> #include <asm/asm-offsets.h> #include <asm/processor-flags.h> +#include <asm/inst.h> /* @@ -345,6 +346,39 @@ For 32-bit we have the following conventions - kernel is built with #endif .endm +#ifdef CONFIG_SMP + +/* + * CPU/node NR is loaded from the limit (size) field of a special segment + * descriptor entry in GDT. + */ +.macro LOAD_CPU_AND_NODE_SEG_LIMIT reg:req + movq $__CPUNODE_SEG, \reg + lsl \reg, \reg +.endm + +/* + * Fetch the per-CPU GSBASE value for this processor and put it in @reg. + * We normally use %gs for accessing per-CPU data, but we are setting up + * %gs here and obviously can not use %gs itself to access per-CPU data. + */ +.macro GET_PERCPU_BASE reg:req + ALTERNATIVE \ + "LOAD_CPU_AND_NODE_SEG_LIMIT \reg", \ + "RDPID \reg", \ + X86_FEATURE_RDPID + andq $VDSO_CPUNODE_MASK, \reg + movq __per_cpu_offset(, \reg, 8), \reg +.endm + +#else + +.macro GET_PERCPU_BASE reg:req + movq pcpu_unit_offsets(%rip), \reg +.endm + +#endif /* CONFIG_SMP */ + /* * This does 'call enter_from_user_mode' unless we can avoid it based on * kernel config or using the static jump infrastructure. diff --git a/arch/x86/include/asm/inst.h b/arch/x86/include/asm/inst.h index f5a796da07f8..d063841a17e3 100644 --- a/arch/x86/include/asm/inst.h +++ b/arch/x86/include/asm/inst.h @@ -306,6 +306,21 @@ .endif MODRM 0xc0 movq_r64_xmm_opd1 movq_r64_xmm_opd2 .endm + +.macro RDPID opd + REG_TYPE rdpid_opd_type \opd + .if rdpid_opd_type == REG_TYPE_R64 + R64_NUM rdpid_opd \opd + .else + R32_NUM rdpid_opd \opd + .endif + .byte 0xf3 + .if rdpid_opd > 7 + PFX_REX rdpid_opd 0 + .endif + .byte 0x0f, 0xc7 + MODRM 0xc0 rdpid_opd 0x7 +.endm #endif #endif
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