x86/vdso: Fix output operand size of RDPID

RDPID instruction outputs to a word-sized register (64-bit on x86_64 and
32-bit on x86_32). Use an unsigned long variable to store the correct size.

LSL outputs to 32-bit register, use %k operand prefix to always print the
32-bit name of the register.

Use RDPID insn mnemonic while at it as the minimum binutils version of
2.30 supports it.

  [ bp: Merge two patches touching the same function into a single one. ]

Fixes: ffebbae ("x86/vdso: Introduce helper functions for CPU and node number")
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250616095315.230620-1-ubizjak@gmail.com

Author: ubizjak

arch/x86/include/asm/segment.h

@@ -244,7 +244,7 @@ static inline unsigned long vdso_encode_cpunode(int cpu, unsigned long node)
 
 static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
 {
-	unsigned int p;
+	unsigned long p;
 
 	/*
 	 * Load CPU and node number from the GDT.  LSL is faster than RDTSCP
@@ -254,10 +254,10 @@ static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
 	 *
 	 * If RDPID is available, use it.
 	 */
-	alternative_io ("lsl %[seg],%[p]",
-			".byte 0xf3,0x0f,0xc7,0xf8", /* RDPID %eax/rax */
+	alternative_io ("lsl %[seg],%k[p]",
+			"rdpid %[p]",
 			X86_FEATURE_RDPID,
-			[p] "=a" (p), [seg] "r" (__CPUNODE_SEG));
+			[p] "=r" (p), [seg] "r" (__CPUNODE_SEG));
 
 	if (cpu)
 		*cpu = (p & VDSO_CPUNODE_MASK);