riscv: use local label names instead of global ones in assembly

Local labels should be prefix by '.L' or they'll be exported in the
symbol table. Additionally, this messes up the backtrace by displaying
an incorrect symbol:

  ...
  [   12.751810] [<ffffffff80441628>] _copy_from_user+0x28/0xc2
  [   12.752035] [<ffffffff800152ca>] handle_misaligned_load+0x1ca/0x2fc
  [   12.752310] [<ffffffff80a033e8>] do_trap_load_misaligned+0x24/0xee
  [   12.752596] [<ffffffff80a0dcae>] _new_vmalloc_restore_context_a0+0xc2/0xce

After:
  ...
  [   10.243916] [<ffffffff804415e4>] _copy_from_user+0x28/0xc2
  [   10.244026] [<ffffffff800152ca>] handle_misaligned_load+0x1ca/0x2fc
  [   10.244150] [<ffffffff80a033a0>] do_trap_load_misaligned+0x24/0xee
  [   10.244268] [<ffffffff80a0dc66>] handle_exception+0x146/0x152

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Fixes: 503638e ("riscv: Stop emitting preventive sfence.vma for new vmalloc mappings")
Link: https://lore.kernel.org/r/20250103141814.508865-1-cleger@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: clementleger

arch/riscv/kernel/entry.S

@@ -23,21 +23,21 @@
 	REG_S 	a0, TASK_TI_A0(tp)
 	csrr 	a0, CSR_CAUSE
 	/* Exclude IRQs */
-	blt  	a0, zero, _new_vmalloc_restore_context_a0
+	blt  	a0, zero, .Lnew_vmalloc_restore_context_a0
 
 	REG_S 	a1, TASK_TI_A1(tp)
 	/* Only check new_vmalloc if we are in page/protection fault */
 	li   	a1, EXC_LOAD_PAGE_FAULT
-	beq  	a0, a1, _new_vmalloc_kernel_address
+	beq  	a0, a1, .Lnew_vmalloc_kernel_address
 	li   	a1, EXC_STORE_PAGE_FAULT
-	beq  	a0, a1, _new_vmalloc_kernel_address
+	beq  	a0, a1, .Lnew_vmalloc_kernel_address
 	li   	a1, EXC_INST_PAGE_FAULT
-	bne  	a0, a1, _new_vmalloc_restore_context_a1
+	bne  	a0, a1, .Lnew_vmalloc_restore_context_a1
 
-_new_vmalloc_kernel_address:
+.Lnew_vmalloc_kernel_address:
 	/* Is it a kernel address? */
 	csrr 	a0, CSR_TVAL
-	bge 	a0, zero, _new_vmalloc_restore_context_a1
+	bge 	a0, zero, .Lnew_vmalloc_restore_context_a1
 
 	/* Check if a new vmalloc mapping appeared that could explain the trap */
 	REG_S	a2, TASK_TI_A2(tp)
@@ -69,7 +69,7 @@ _new_vmalloc_kernel_address:
 	/* Check the value of new_vmalloc for this cpu */
 	REG_L	a2, 0(a0)
 	and	a2, a2, a1
-	beq	a2, zero, _new_vmalloc_restore_context
+	beq	a2, zero, .Lnew_vmalloc_restore_context
 
 	/* Atomically reset the current cpu bit in new_vmalloc */
 	amoxor.d	a0, a1, (a0)
@@ -83,11 +83,11 @@ _new_vmalloc_kernel_address:
 	csrw	CSR_SCRATCH, x0
 	sret
 
-_new_vmalloc_restore_context:
+.Lnew_vmalloc_restore_context:
 	REG_L 	a2, TASK_TI_A2(tp)
-_new_vmalloc_restore_context_a1:
+.Lnew_vmalloc_restore_context_a1:
 	REG_L 	a1, TASK_TI_A1(tp)
-_new_vmalloc_restore_context_a0:
+.Lnew_vmalloc_restore_context_a0:
 	REG_L	a0, TASK_TI_A0(tp)
 .endm