diff options
| author | James Clarke <jrtc27@jrtc27.com> | 2020-02-03 00:53:17 +0000 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2020-02-02 16:53:17 -0800 |
| commit | 2c4e689bc1ed4440d0d95b3b350ce872e7f75865 (patch) | |
| tree | 136e0fefebe6ec544c101b4e04bb56a85ede57f1 | |
| parent | 6fa3555cc501ab1dfb034061e991e065e2e54253 (diff) | |
| download | pk-2c4e689bc1ed4440d0d95b3b350ce872e7f75865.zip pk-2c4e689bc1ed4440d0d95b3b350ce872e7f75865.tar.gz pk-2c4e689bc1ed4440d0d95b3b350ce872e7f75865.tar.bz2 | |
Support manually zeroing out BSS when booting (#188)
Some ELF loaders, in particular gdb's load command for dynamically
loading files into memory, which is often used to load binaries onto
FPGAs over JTAG, do not zero out BSS, leaving the memory in whatever
state it was previously in. Thus, introduce a new --enable-zero-bss
configure flag, which will include code to zero out BSS when booting.
| -rw-r--r-- | config.h.in | 3 | ||||
| -rwxr-xr-x | configure | 15 | ||||
| -rw-r--r-- | configure.ac | 5 | ||||
| -rw-r--r-- | machine/mentry.S | 16 |
4 files changed, 38 insertions, 1 deletions
diff --git a/config.h.in b/config.h.in index dbacd78..98763ac 100644 --- a/config.h.in +++ b/config.h.in @@ -56,3 +56,6 @@ /* Define if subproject MCPPBS_SPROJ_NORM is enabled */ #undef UTIL_ENABLED + +/* Define if BSS should be manually zeroed when booting */ +#undef ZERO_BSS @@ -675,6 +675,7 @@ with_arch with_abi enable_print_device_tree with_mem_start +enable_zero_bss enable_optional_subprojects enable_vm enable_logo @@ -1314,6 +1315,7 @@ Optional Features: --enable-stow Enable stow-based install --enable-print-device-tree Print DTS when booting + --enable-zero-bss Manually zero out BSS when booting --enable-optional-subprojects Enable all optional subprojects --disable-vm Disable virtual memory @@ -4122,6 +4124,19 @@ else fi +# Check whether --enable-zero-bss was given. +if test "${enable_zero_bss+set}" = set; then : + enableval=$enable_zero_bss; +fi + +if test "x$enable_zero_bss" = "xyes"; then : + + +$as_echo "#define ZERO_BSS /**/" >>confdefs.h + + +fi + #------------------------------------------------------------------------- # MCPPBS subproject list #------------------------------------------------------------------------- diff --git a/configure.ac b/configure.ac index 1653f2b..81492de 100644 --- a/configure.ac +++ b/configure.ac @@ -107,6 +107,11 @@ AC_ARG_WITH([mem-start], AS_HELP_STRING([--with-mem-start], [Set physical memory AC_SUBST([MEM_START], [0x80000000], [Physical memory start address]) ]) +AC_ARG_ENABLE([zero-bss], AS_HELP_STRING([--enable-zero-bss], [Manually zero out BSS when booting])) +AS_IF([test "x$enable_zero_bss" = "xyes"], [ + AC_DEFINE([ZERO_BSS],,[Define if BSS should be manually zeroed when booting]) +]) + #------------------------------------------------------------------------- # MCPPBS subproject list #------------------------------------------------------------------------- diff --git a/machine/mentry.S b/machine/mentry.S index 84bd3c1..9ec9916 100644 --- a/machine/mentry.S +++ b/machine/mentry.S @@ -267,9 +267,23 @@ do_reset: slli a2, a3, RISCV_PGSHIFT add sp, sp, a2 + bnez a3, .LmultiHartInit + +#ifdef ZERO_BSS + # Zero out BSS; linker script provides alignment and padding + la t0, _fbss + la t1, _end + beq t0, t1, 2f +1:STORE zero, 0(t0) + addi t0, t0, REGBYTES + bne t0, t1, 1b +2: +#endif + # Boot on the first hart - beqz a3, init_first_hart + j init_first_hart +.LmultiHartInit: # set MSIE bit to receive IPI li a2, MIP_MSIP csrw mie, a2 |