The following commit has been merged into the x86/fsgsbase branch of tip: Commit-ID: eaad981291ee36efee15a5e515d4598ae94ace07 Gitweb: https://git.kernel.org/tip/eaad981291ee36efee15a5e515d4598ae94ace07 Author: Chang S. Bae <[email protected]> AuthorDate: Thu, 28 May 2020 16:13:56 -04:00 Committer: Thomas Gleixner <[email protected]> CommitterDate: Thu, 18 Jun 2020 15:47:04 +02:00
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 2.23 do not support it. Support is added in version 2.27. [ tglx: Massaged changelog ] Suggested-by: H. Peter Anvin <[email protected]> Signed-off-by: Chang S. Bae <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Signed-off-by: Sasha Levin <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Link: https://lkml.kernel.org/r/[email protected] Link: https://lkml.kernel.org/r/[email protected] --- 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 4208c1e..5c0cbb4 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> /* @@ -351,3 +352,36 @@ For 32-bit we have the following conventions - kernel is built with call stackleak_erase #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 */ diff --git a/arch/x86/include/asm/inst.h b/arch/x86/include/asm/inst.h index f5a796d..d063841 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
