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x86/cpu: Provide the full setup for getcpu() on x86-32

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setup_getcpu() configures two things:

  - it writes the current CPU & node information into MSR_TSC_AUX
  - it writes the same information as a GDT entry.

By using the "full" setup_getcpu() on i386 it is possible to read the CPU
information in userland via RDTSCP() or via LSL from the GDT.

Provide an GDT_ENTRY_CPUNODE for x86-32 and make the setup function
unconditionally available.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Roland Mainz <roland.mainz@nrubsig.org>
Link: https://lore.kernel.org/r/20221125094216.3663444-2-bigeasy@linutronix.de
This commit is contained in:
Sebastian Andrzej Siewior 2022-11-25 10:42:14 +01:00 • committed by Thomas Gleixner
parent 4c382d723e
commit 717cce3bdc
2 changed files with 5 additions and 7 deletions
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8
arch/x86/include/asm/segment.h
View file

@ -96,7 +96,7 @@
*
* 26 - ESPFIX small SS
* 27 - per-cpu [ offset to per-cpu data area ]
* 28 - unused
* 28 - VDSO getcpu
* 29 - unused
* 30 - unused
* 31 - TSS for double fault handler
@ -119,6 +119,7 @@
#define GDT_ENTRY_ESPFIX_SS 26
#define GDT_ENTRY_PERCPU 27
#define GDT_ENTRY_CPUNODE 28
#define GDT_ENTRY_DOUBLEFAULT_TSS 31
@ -159,6 +160,8 @@
# define __KERNEL_PERCPU 0
#endif
#define __CPUNODE_SEG (GDT_ENTRY_CPUNODE*8 + 3)
#else /* 64-bit: */
#include <asm/cache.h>
@ -226,8 +229,6 @@
#define GDT_ENTRY_TLS_ENTRIES 3
#define TLS_SIZE (GDT_ENTRY_TLS_ENTRIES* 8)
#ifdef CONFIG_X86_64
/* Bit size and mask of CPU number stored in the per CPU data (and TSC_AUX) */
#define VDSO_CPUNODE_BITS 12
#define VDSO_CPUNODE_MASK 0xfff
@ -265,7 +266,6 @@ static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
}
#endif /* !__ASSEMBLY__ */
#endif /* CONFIG_X86_64 */
#ifdef __KERNEL__

4
arch/x86/kernel/cpu/common.c
View file

@ -2124,7 +2124,6 @@ static void wait_for_master_cpu(int cpu)
#endif
}
#ifdef CONFIG_X86_64
static inline void setup_getcpu(int cpu)
{
unsigned long cpudata = vdso_encode_cpunode(cpu, early_cpu_to_node(cpu));
@ -2146,6 +2145,7 @@ static inline void setup_getcpu(int cpu)
write_gdt_entry(get_cpu_gdt_rw(cpu), GDT_ENTRY_CPUNODE, &d, DESCTYPE_S);
}
#ifdef CONFIG_X86_64
static inline void ucode_cpu_init(int cpu)
{
if (cpu)
@ -2165,8 +2165,6 @@ static inline void tss_setup_ist(struct tss_struct *tss)
#else /* CONFIG_X86_64 */
static inline void setup_getcpu(int cpu) { }
static inline void ucode_cpu_init(int cpu)
{
show_ucode_info_early();