elfloader, RISC-V: Move the elfloader during boot

The SBI implementation usually loads the elfloader where the kernel would prefer to also be loaded. Allow the elfloader to move itself to a higher address before loading the kernel and user images. This requires ensuring that the stacks are not overwritten during the merge, and so must be placed before the _archive_cpio section in the linker script. Signed-off-by: Kent McLeod <[email protected]>
seL4 · Feb 22, 2022 · 9dd2537 · 9dd2537
1 parent 83064a6
commit 9dd2537
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Showing 4 changed files with 25 additions and 8 deletions.
diff --git a/cmake-tool/helpers/application_settings.cmake b/cmake-tool/helpers/application_settings.cmake
@@ -49,9 +49,6 @@ function(ApplyData61ElfLoaderSettings kernel_platform kernel_sel4_arch)
     if(KernelPlatformZynqmp AND KernelSel4ArchAarch32)
         set(IMAGE_START_ADDR 0x8000000 CACHE INTERNAL "" FORCE)
     endif()
-    if(KernelPlatformSpike AND KernelSel4ArchRiscV32)
-        set(IMAGE_START_ADDR 0x80400000 CACHE INTERNAL "" FORCE)
-    endif()
 endfunction()
 
 function(ApplyCommonSimulationSettings kernel_sel4_arch)

diff --git a/elfloader-tool/src/arch-riscv/boot.c b/elfloader-tool/src/arch-riscv/boot.c
@@ -59,7 +59,10 @@ unsigned long l2pt[PTES_PER_PT] __attribute__((aligned(4096)));
 unsigned long l2pt_elf[PTES_PER_PT] __attribute__((aligned(4096)));
 #endif
 
-char elfloader_stack_alloc[BIT(CONFIG_KERNEL_STACK_BITS)];
+/* This stack cannot go in the .bss section because it's already in use when the
+ * .bss section is zeroed.
+ */
+char elfloader_stack_alloc[BIT(CONFIG_KERNEL_STACK_BITS)] __attribute__((section(".data"))) ;
 
 /* first HART will initialise these */
 void const *dtb = NULL;

diff --git a/elfloader-tool/src/arch-riscv/crt0.S b/elfloader-tool/src/arch-riscv/crt0.S
@@ -58,7 +58,22 @@ _start:
   /* Attach the stack to sp before calling any C functions */
   la sp, (elfloader_stack_alloc + BIT(12))
 
+  /*
+   * Binary images may not be loaded in the correct location.
+   * Try and move ourselves so we're in the right place.
+   */
+  jal fixup_image_base
+  /* fixup_image_base returns 0 if no need to move */
+  beqz     a0, 1f
+
+  /* otherwise, restore args and jump to the start of the new elfloader */
+  mv a2, a0
+  mv a0, s0
+  mv a1, s2
+  jr a2
+
 /* Clear the BSS before we get to do anything more specific */
+1:
   jal clear_bss
 
   /* Check if the Heart State Management (HSM) extension exists, so it can be

diff --git a/elfloader-tool/src/arch-riscv/linker.lds b/elfloader-tool/src/arch-riscv/linker.lds
@@ -32,10 +32,6 @@ SECTIONS
         /*
          * ld crashes when we add this here: *(_driver_list)
          */
-        . = ALIGN(16);
-        _archive_start = .;
-        *(._archive_cpio)
-        _archive_end = .;
     }
     . = ALIGN(16);
     .data :
@@ -46,6 +42,12 @@ SECTIONS
         *(.data.*)
     }
     . = ALIGN(16);
+    ._archive_cpio : {
+        _archive_start = .;
+        *(._archive_cpio)
+        _archive_end = .;
+    }
+    . = ALIGN(16);
     .bss :
     {
         _bss = .;