Merge tag 'riscv-for-linus-5.17-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux

Pull RISC-V fixes from Palmer Dabbelt:

 - prevent users from enabling the alternatives framework (and thus
   errata handling) on XIP kernels, where runtime code patching does not
   function correctly.

 - properly detect offset overflow for AUIPC-based relocations in
   modules. This may manifest as modules calling arbitrary invalid
   addresses, depending on the address allocated when a module is
   loaded.

* tag 'riscv-for-linus-5.17-rc8' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux:
  riscv: Fix auipc+jalr relocation range checks
  riscv: alternative only works on !XIP_KERNEL

3 files changed, 19 insertions, 7 deletions

diff --git a/arch/riscv/Kconfig.erratas b/arch/riscv/Kconfig.erratas
index b44d6ecdb46e..0aacd7052585 100644
--- a/arch/riscv/Kconfig.erratas
+++ b/arch/riscv/Kconfig.erratas
@@ -2,6 +2,7 @@ menu "CPU errata selection"
 
 config RISCV_ERRATA_ALTERNATIVE
 	bool "RISC-V alternative scheme"
+	depends on !XIP_KERNEL
 	default y
 	help
 	  This Kconfig allows the kernel to automatically patch the
diff --git a/arch/riscv/Kconfig.socs b/arch/riscv/Kconfig.socs
index 6ec44a22278a..c112ab2a9052 100644
--- a/arch/riscv/Kconfig.socs
+++ b/arch/riscv/Kconfig.socs
@@ -14,8 +14,8 @@ config SOC_SIFIVE
 	select CLK_SIFIVE
 	select CLK_SIFIVE_PRCI
 	select SIFIVE_PLIC
-	select RISCV_ERRATA_ALTERNATIVE
-	select ERRATA_SIFIVE
+	select RISCV_ERRATA_ALTERNATIVE if !XIP_KERNEL
+	select ERRATA_SIFIVE if !XIP_KERNEL
 	help
 	  This enables support for SiFive SoC platform hardware.
 
diff --git a/arch/riscv/kernel/module.c b/arch/riscv/kernel/module.c
index 68a9e3d1fe16..4a48287513c3 100644
--- a/arch/riscv/kernel/module.c
+++ b/arch/riscv/kernel/module.c
@@ -13,6 +13,19 @@
 #include <linux/pgtable.h>
 #include <asm/sections.h>
 
+/*
+ * The auipc+jalr instruction pair can reach any PC-relative offset
+ * in the range [-2^31 - 2^11, 2^31 - 2^11)
+ */
+static bool riscv_insn_valid_32bit_offset(ptrdiff_t val)
+{
+#ifdef CONFIG_32BIT
+	return true;
+#else
+	return (-(1L << 31) - (1L << 11)) <= val && val < ((1L << 31) - (1L << 11));
+#endif
+}
+
 static int apply_r_riscv_32_rela(struct module *me, u32 *location, Elf_Addr v)
 {
 	if (v != (u32)v) {
@@ -95,7 +108,7 @@ static int apply_r_riscv_pcrel_hi20_rela(struct module *me, u32 *location,
 	ptrdiff_t offset = (void *)v - (void *)location;
 	s32 hi20;
 
-	if (offset != (s32)offset) {
+	if (!riscv_insn_valid_32bit_offset(offset)) {
 		pr_err(
 		  "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
 		  me->name, (long long)v, location);
@@ -197,10 +210,9 @@ static int apply_r_riscv_call_plt_rela(struct module *me, u32 *location,
 				       Elf_Addr v)
 {
 	ptrdiff_t offset = (void *)v - (void *)location;
-	s32 fill_v = offset;
 	u32 hi20, lo12;
 
-	if (offset != fill_v) {
+	if (!riscv_insn_valid_32bit_offset(offset)) {
 		/* Only emit the plt entry if offset over 32-bit range */
 		if (IS_ENABLED(CONFIG_MODULE_SECTIONS)) {
 			offset = module_emit_plt_entry(me, v);
@@ -224,10 +236,9 @@ static int apply_r_riscv_call_rela(struct module *me, u32 *location,
 				   Elf_Addr v)
 {
 	ptrdiff_t offset = (void *)v - (void *)location;
-	s32 fill_v = offset;
 	u32 hi20, lo12;
 
-	if (offset != fill_v) {
+	if (!riscv_insn_valid_32bit_offset(offset)) {
 		pr_err(
 		  "%s: target %016llx can not be addressed by the 32-bit offset from PC = %p\n",
 		  me->name, (long long)v, location);