Unify and fix RISC-V symbol names

book/src/to-contribute/style-guidelines/asm-guidelines.md

@@ -49,6 +49,13 @@ foo:
 The assembler treats the directives `.global` and `.globl` as the same.
 For clarity, however, `.global` is preferred.
 
+Note that a Rust crate is a single translation unit, so `global_asm!` labels in
+different modules within the same crate share the same global namespace. In RISC-V,
+we have experienced that defining two labels with the same name in different modules
+can nondeterministically cause duplicate symbol error. The `.L` prefix does not help.
+Therefore, add custom prefixes to your labels to avoid name clashes. Nevertheless,
+use `.global` to export symbols that need to be visible within the same crate.
+
 In x86-64, if an executable section contains a mix of 32-bit and 64-bit code,
 the `.code64` and `.code32` directives are treated as function attributes.
 ```asm

ostd/src/arch/loongarch/boot/bsp_boot.S

@@ -34,6 +34,7 @@
 
 .section ".boot", "awx", @progbits
 
+# `_start` is also the entrypoint specified in the linker script.
 .global _start
 _start:
     # Set DMW0 (kernel)

ostd/src/arch/loongarch/boot/mod.rs

@@ -19,7 +19,7 @@ use crate::{
     mm::paddr_to_vaddr,
 };
 
-global_asm!(include_str!("boot.S"));
+global_asm!(include_str!("bsp_boot.S"));
 
 static EFI_SYSTEM_TABLE: Once<&'static EfiSystemTable> = Once::new();
 

ostd/src/arch/riscv/boot/ap_boot.S

@@ -35,7 +35,7 @@ ap_boot_start:
     # Check if the write to satp succeeds.
     # Reference: <https://riscv.github.io/riscv-isa-manual/snapshot/privileged/#satp>.
     csrr    t3, satp
-    beq     t3, t1, flush_tlb_ap
+    beq     t3, t1, ap_flush_tlb
 
     # This AP doesn't support Sv48. So the `__ap_boot_page_table_pointer` must
     # point to a Sv39 page table since we assume that all harts support a same
@@ -47,13 +47,13 @@ ap_boot_start:
 
     # Check again if the write to satp succeeds.
     csrr    t0, satp
-    beq     t0, t1, flush_tlb_ap
+    beq     t0, t1, ap_flush_tlb
 
     # If the CPU doesn't support either Sv48 or Sv39 this is actually reachable.
-unreachable_pa_ap:
-    j      unreachable_pa_ap
+ap_unreachable_pa:
+    j       ap_unreachable_pa
 
-flush_tlb_ap:
+ap_flush_tlb:
     sfence.vma                          # Flush TLB.
     
     # Now we need to switch to virtual addressing.
@@ -87,11 +87,11 @@ __ap_boot_cpu_id_tail:
 ap_boot_virtual:
     # Atomically update the CPU ID tail and load the previous value to t1.
     lla     t0, __ap_boot_cpu_id_tail
-cmpxchg_load:
+ap_cmpxchg_load:
     lr.d    t1, (t0)
     addi    t2, t1, 1
     sc.d    t2, t2, (t0)
-    bnez    t2, cmpxchg_load
+    bnez    t2, ap_cmpxchg_load
 
     # Get the AP boot info array pointer using absolute addressing.
     lla     t2, __ap_boot_info_array_pointer
@@ -118,5 +118,5 @@ cmpxchg_load:
     lla     t1, riscv_ap_early_entry
     jr      t1
 
-unreachable_va_ap:
-    j      unreachable_va_ap
+ap_unreachable_va:
+    j       ap_unreachable_va

ostd/src/arch/riscv/boot/bsp_boot.S

@@ -19,6 +19,7 @@ KERNEL_VMA_OFFSET      = 0xffffffff00000000
 
 .section ".boot", "awx", @progbits
 
+# `_start` is also the entrypoint specified in the linker script.
 .global _start
 _start:
     # Arguments passed from SBI:
@@ -46,7 +47,7 @@ _start:
     # Check if the write to satp succeeds. If not, try Sv39.
     # Reference: <https://riscv.github.io/riscv-isa-manual/snapshot/privileged/#satp>.
     csrr   t1, satp
-    beq    t0, t1, flush_tlb_bsp
+    beq    t0, t1, bsp_flush_tlb
 
     # Try loading the Sv39 page table.
     lla     t0, sv39_boot_l3pt
@@ -57,20 +58,20 @@ _start:
 
     # Check again if the write to satp succeeds.
     csrr   t1, satp
-    beq    t0, t1, flush_tlb_bsp
+    beq    t0, t1, bsp_flush_tlb
 
     # If the CPU doesn't support either Sv48 or Sv39 this is actually reachable.
-unreachable_pa_bsp:
-    j      unreachable_pa_bsp
+bsp_unreachable_pa:
+    j      bsp_unreachable_pa
 
-flush_tlb_bsp:
+bsp_flush_tlb:
     sfence.vma
 
     # Update SP/PC to use the virtual address.
     li     t1, KERNEL_VMA_OFFSET
     lla    sp, boot_stack_top
     or     sp, sp, t1
-    lla    t0, _start_virt - KERNEL_VMA_OFFSET
+    lla    t0, bsp_boot_virt - KERNEL_VMA_OFFSET
     or     t0, t0, t1
     jr     t0
 
@@ -120,7 +121,7 @@ boot_stack_top:
 
 .text
 
-_start_virt:
+bsp_boot_virt:
     # Initialize GP to the CPU-local storage's base address.
 .extern __cpu_local_start
     lla    gp, __cpu_local_start
@@ -129,5 +130,5 @@ _start_virt:
     lla    t0, riscv_boot
     jr     t0
 
-unreachable_va_bsp:
-    j      unreachable_va_bsp
+bsp_unreachable_va:
+    j      bsp_unreachable_va

ostd/src/arch/riscv/boot/mod.rs

@@ -18,7 +18,7 @@ use crate::{
     mm::paddr_to_vaddr,
 };
 
-global_asm!(include_str!("boot.S"));
+global_asm!(include_str!("bsp_boot.S"));
 
 /// The Flattened Device Tree of the platform.
 pub static DEVICE_TREE: Once<Fdt> = Once::new();