Commit 717cce3b authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Thomas Gleixner
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x86/cpu: Provide the full setup for getcpu() on x86-32 



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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarRoland Mainz <roland.mainz@nrubsig.org>
Link: https://lore.kernel.org/r/20221125094216.3663444-2-bigeasy@linutronix.de
parent 4c382d72

arch/x86/include/asm/segment.h

+4 −4
Original line number Diff line number Diff line
@@ -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__

arch/x86/kernel/cpu/common.c

+1 −3
Original line number Diff line number Diff line
@@ -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();