RISC-V Patches for 5.1-rc4

I dropped the ball a bit here: these patches should all probably have
 been part of rc2, but I wanted to get around to properly testing them in
 the various configurations (qemu32, qeum64, unleashed) first.
 Unfortunately I've been traveling and didn't have time to actually do
 that, but since these fix concrete bugs and pass my old set of tests I
 don't want to delay the fixes any longer.
 
 There are four independent fixes here:
 
 * A fix for the rv32 port that corrects the 64-bit user accesor's fixup
   label address.
 * A fix for a regression introduced during the merge window that broke
   medlow configurations at run time.  This patch also includes a fix
   that disables ftrace for the same set of functions, which was found by
   inspection at the same time.
 * A modification of the memory map to avoid overlapping the FIXMAP and
   VMALLOC regions on systems with small memory maps.
 * A fix to the module handling code to use the correct syntax for
   probing Kconfig entries.
 
 These have passed my standard test flow, but I didn't have time to
 expand that like I said I would.
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Merge tag 'riscv-for-linus-5.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux

Pull RISC-V fixes from Palmer Dabbelt:
 "I dropped the ball a bit here: these patches should all probably have
  been part of rc2, but I wanted to get around to properly testing them
  in the various configurations (qemu32, qeum64, unleashed) first.

  Unfortunately I've been traveling and didn't have time to actually do
  that, but since these fix concrete bugs and pass my old set of tests I
  don't want to delay the fixes any longer.

  There are four independent fixes here:

   - A fix for the rv32 port that corrects the 64-bit user accesor's
     fixup label address.

   - A fix for a regression introduced during the merge window that
     broke medlow configurations at run time. This patch also includes a
     fix that disables ftrace for the same set of functions, which was
     found by inspection at the same time.

   - A modification of the memory map to avoid overlapping the FIXMAP
     and VMALLOC regions on systems with small memory maps.

   - A fix to the module handling code to use the correct syntax for
     probing Kconfig entries.

  These have passed my standard test flow, but I didn't have time to
  expand that testing like I said I would"

* tag 'riscv-for-linus-5.1-rc4' of git://git.kernel.org/pub/scm/linux/kernel/git/palmer/riscv-linux:
  RISC-V: Use IS_ENABLED(CONFIG_CMODEL_MEDLOW)
  RISC-V: Fix FIXMAP_TOP to avoid overlap with VMALLOC area
  RISC-V: Always compile mm/init.c with cmodel=medany and notrace
  riscv: fix accessing 8-byte variable from RV32

arch/riscv/include/asm/fixmap.h

@@ -26,7 +26,7 @@ enum fixed_addresses {
 };
 
 #define FIXADDR_SIZE		(__end_of_fixed_addresses * PAGE_SIZE)
-#define FIXADDR_TOP		(PAGE_OFFSET)
+#define FIXADDR_TOP		(VMALLOC_START)
 #define FIXADDR_START		(FIXADDR_TOP - FIXADDR_SIZE)
 
 #define FIXMAP_PAGE_IO		PAGE_KERNEL

arch/riscv/include/asm/uaccess.h

@@ -300,7 +300,7 @@ do {								\
 		"	.balign 4\n"				\
 		"4:\n"						\
 		"	li %0, %6\n"				\
-		"	jump 2b, %1\n"				\
+		"	jump 3b, %1\n"				\
 		"	.previous\n"				\
 		"	.section __ex_table,\"a\"\n"		\
 		"	.balign " RISCV_SZPTR "\n"			\

arch/riscv/kernel/Makefile

@@ -4,7 +4,6 @@
 
 ifdef CONFIG_FTRACE
 CFLAGS_REMOVE_ftrace.o = -pg
-CFLAGS_REMOVE_setup.o = -pg
 endif
 
 extra-y += head.o
@@ -29,8 +28,6 @@ obj-y	+= vdso.o
 obj-y	+= cacheinfo.o
 obj-y	+= vdso/
 
-CFLAGS_setup.o := -mcmodel=medany
-
 obj-$(CONFIG_FPU)		+= fpu.o
 obj-$(CONFIG_SMP)		+= smpboot.o
 obj-$(CONFIG_SMP)		+= smp.o

arch/riscv/kernel/module.c

@@ -141,7 +141,7 @@ static int apply_r_riscv_hi20_rela(struct module *me, u32 *location,
 {
 	s32 hi20;
 
-	if (IS_ENABLED(CMODEL_MEDLOW)) {
+	if (IS_ENABLED(CONFIG_CMODEL_MEDLOW)) {
 		pr_err(
 		  "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
 		  me->name, (long long)v, location);

arch/riscv/kernel/setup.c

@@ -48,14 +48,6 @@ struct screen_info screen_info = {
 };
 #endif
 
-unsigned long va_pa_offset;
-EXPORT_SYMBOL(va_pa_offset);
-unsigned long pfn_base;
-EXPORT_SYMBOL(pfn_base);
-
-unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)] __page_aligned_bss;
-EXPORT_SYMBOL(empty_zero_page);
-
 /* The lucky hart to first increment this variable will boot the other cores */
 atomic_t hart_lottery;
 unsigned long boot_cpu_hartid;

arch/riscv/mm/Makefile

@@ -1,3 +1,9 @@
+
+CFLAGS_init.o := -mcmodel=medany
+ifdef CONFIG_FTRACE
+CFLAGS_REMOVE_init.o = -pg
+endif
+
 obj-y += init.o
 obj-y += fault.o
 obj-y += extable.o

arch/riscv/mm/init.c

@@ -25,6 +25,10 @@
 #include <asm/pgtable.h>
 #include <asm/io.h>
 
+unsigned long empty_zero_page[PAGE_SIZE / sizeof(unsigned long)]
+							__page_aligned_bss;
+EXPORT_SYMBOL(empty_zero_page);
+
 static void __init zone_sizes_init(void)
 {
 	unsigned long max_zone_pfns[MAX_NR_ZONES] = { 0, };
@@ -143,6 +147,11 @@ void __init setup_bootmem(void)
 	}
 }
 
+unsigned long va_pa_offset;
+EXPORT_SYMBOL(va_pa_offset);
+unsigned long pfn_base;
+EXPORT_SYMBOL(pfn_base);
+
 pgd_t swapper_pg_dir[PTRS_PER_PGD] __page_aligned_bss;
 pgd_t trampoline_pg_dir[PTRS_PER_PGD] __initdata __aligned(PAGE_SIZE);
 
@@ -172,6 +181,25 @@ void __set_fixmap(enum fixed_addresses idx, phys_addr_t phys, pgprot_t prot)
 	}
 }
 
+/*
+ * setup_vm() is called from head.S with MMU-off.
+ *
+ * Following requirements should be honoured for setup_vm() to work
+ * correctly:
+ * 1) It should use PC-relative addressing for accessing kernel symbols.
+ *    To achieve this we always use GCC cmodel=medany.
+ * 2) The compiler instrumentation for FTRACE will not work for setup_vm()
+ *    so disable compiler instrumentation when FTRACE is enabled.
+ *
+ * Currently, the above requirements are honoured by using custom CFLAGS
+ * for init.o in mm/Makefile.
+ */
+
+#ifndef __riscv_cmodel_medany
+#error "setup_vm() is called from head.S before relocate so it should "
+	"not use absolute addressing."
+#endif
+
 asmlinkage void __init setup_vm(void)
 {
 	extern char _start;