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| author | Chang S. Bae <chang.seok.bae@intel.com> | 2020-05-28 16:13:56 -0400 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2020-06-18 15:47:04 +0200 |
| commit | eaad981291ee36efee15a5e515d4598ae94ace07 (patch) | |
| tree | 0e3621526e6d949461a6a25f0f704cac93a2c31d /arch/x86/entry/calling.h | |
| parent | 96b2371413e8f636a5f25c42a933af21c35a2a41 (diff) | |
| download | linux-eaad981291ee36efee15a5e515d4598ae94ace07.tar.gz | |
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 <hpa@zytor.com> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sasha Levin <sashal@kernel.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/1557309753-24073-12-git-send-email-chang.seok.bae@intel.com Link: https://lkml.kernel.org/r/20200528201402.1708239-11-sashal@kernel.org
Diffstat (limited to 'arch/x86/entry/calling.h')
| -rw-r--r-- | arch/x86/entry/calling.h | 34 |
1 files changed, 34 insertions, 0 deletions
diff --git a/arch/x86/entry/calling.h b/arch/x86/entry/calling.h index 4208c1e3f601..5c0cbb443030 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 */ |