[riscv] Add debug printing of hexadecimal values in libprefix.S

Add millicode routines to print hexadecimal values (with any number of
digits), and macros to print register contents or symbol addresses.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

diff --git a/src/arch/riscv/prefix/libprefix.S b/src/arch/riscv/prefix/libprefix.S
index 1a2b992d660f4381b9064441ccfb3b01de7ef39d..7f4e2bc98710d4c9689b4fd9413a5218cd3627b9 100644 (file)
--- a/src/arch/riscv/prefix/libprefix.S
+++ b/src/arch/riscv/prefix/libprefix.S
@@ -77,8 +77,9 @@ print_message:
 print_message_alt:
        /* Register usage:
         *
-        * t0 - character pointer
         * a0 - current character
+        * t0 - alternate link register
+        * t1 - character pointer
         * t2 - preserved a0
         * t3 - preserved a1
         * t4 - preserved a6
@@ -121,6 +122,97 @@ progress_\@:
 #endif
        .endm
 
+/*****************************************************************************
+ *
+ * Print hexadecimal value to debug console
+ *
+ *****************************************************************************
+ *
+ * Print a register value in hexadecimal to the debug console.
+ *
+ * This function does not require a valid stack.
+ *
+ * Note that the parameters are passed in registers t1 and t2 (rather
+ * than a0) and all non-temporary registers are preserved.
+ *
+ * Parameters:
+ *
+ *   t1 - Value to print
+ *   t2 - Number of bits to print (must be a multiple of 4)
+ *
+ * Returns: none
+ *
+ */
+       .section ".prefix.print_hex_value", "ax", @progbits
+       .globl  print_hex_value
+print_hex_value:
+       /* Handle alternate link register */
+       mv      t0, ra
+print_hex_value_alt:
+       /* Register usage:
+        *
+        * a0 - current digit / general temporary
+        * t0 - alternate link register
+        * t1 - current value
+        * t2 - digit counter
+        * t3 - preserved a0
+        * t4 - preserved a1
+        * t5 - preserved a6
+        * t6 - preserved a7
+        */
+       mv      t3, a0
+       mv      t4, a1
+       mv      t5, a6
+       mv      t6, a7
+
+       /* Skip any unprinted digits */
+       li      a0, __riscv_xlen
+       sub     a0, a0, t2
+       sll     t1, t1, a0
+
+1:     /* Print each digit in turn */
+       srli    a0, t1, ( __riscv_xlen - 4 )
+       addi    a0, a0, -10
+       bltz    a0, 2f
+       addi    a0, a0, ( 'a' - ( '0' + 10 ) )
+2:     addi    a0, a0, ( '0' + 10 )
+       li      a7, SBI_DBCN
+       li      a6, SBI_DBCN_WRITE_BYTE
+       ecall
+       slli    t1, t1, 4
+       addi    t2, t2, -4
+       bgtz    t2, 1b
+
+       /* Restore registers and return (via alternate link register) */
+       mv      a7, t6
+       mv      a6, t5
+       mv      a1, t4
+       mv      a0, t3
+       jr      t0
+       .size   print_hex_value, . - print_hex_value
+
+       /*
+        * Display hexadecimal register value (if debugging is enabled)
+        */
+       .macro  print_hex_reg reg, bits=__riscv_xlen
+#ifndef NDEBUG
+       mv      t1, \reg
+       li      t2, \bits
+       jal     t0, print_hex_value_alt
+#endif
+       .endm
+
+       /*
+        * Display hexadecimal symbol address (if debugging is enabled)
+        */
+       .macro  print_hex_addr sym
+#ifndef NDEBUG
+       la      t1, \sym
+       li      t2, __riscv_xlen
+       jal     t0, print_hex_value_alt
+#endif
+       .endm
+
 /*****************************************************************************
  *
  * Apply compressed relocation records