The following commit has been merged into the x86/vdso branch of tip:
Commit-ID: 717cce3bdcf34705417f641bf2fcdf9b038ec36c
Gitweb: https://git.kernel.org/tip/717cce3bdcf34705417f641bf2fcdf9b038ec36c
Author: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
AuthorDate: Fri, 25 Nov 2022 10:42:14 +01:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Mon, 06 Feb 2023 15:48:54 +01:00
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: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Roland Mainz <roland.mainz@xxxxxxxxxxx>
Link: https://lore.kernel.org/r/20221125094216.3663444-2-bigeasy@xxxxxxxxxxxxx
---
arch/x86/include/asm/segment.h | 8 ++++----
arch/x86/kernel/cpu/common.c | 4 +---
2 files changed, 5 insertions(+), 7 deletions(-)
diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index c390a67..794f696 100644
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -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__
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 3a9043e..a26ce20 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -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();
|