diff mbox series

[v5,1/1] riscv: Allow to downgrade paging mode from the command line

Message ID 20230222104322.1197763-2-alexghiti@rivosinc.com (mailing list archive)
State Superseded
Headers show
Series riscv: Allow to downgrade paging mode from the command line | expand

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conchuod/maintainers_pattern success MAINTAINERS pattern errors before the patch: 13 and now 13
conchuod/verify_signedoff success Signed-off-by tag matches author and committer
conchuod/kdoc success Errors and warnings before: 0 this patch: 0
conchuod/build_rv64_clang_allmodconfig fail Failed to build the tree with this patch.
conchuod/module_param success Was 0 now: 0
conchuod/build_rv64_gcc_allmodconfig fail Failed to build the tree with this patch.
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conchuod/build_rv32_defconfig fail Build failed
conchuod/dtb_warn_rv64 success Errors and warnings before: 2 this patch: 2
conchuod/header_inline success No static functions without inline keyword in header files
conchuod/checkpatch warning CHECK: Consider using #include <linux/pgtable.h> instead of <asm/pgtable.h> WARNING: added, moved or deleted file(s), does MAINTAINERS need updating?
conchuod/source_inline success Was 0 now: 0
conchuod/build_rv64_nommu_k210_defconfig fail Build failed
conchuod/verify_fixes success No Fixes tag
conchuod/build_rv64_nommu_virt_defconfig fail Build failed

Commit Message

Alexandre Ghiti Feb. 22, 2023, 10:43 a.m. UTC 
Add 2 early command line parameters that allow to downgrade satp mode
(using the same naming as x86):
- "no5lvl": use a 4-level page table (down from sv57 to sv48)
- "no4lvl": use a 3-level page table (down from sv57/sv48 to sv39)

Note that going through the device tree to get the kernel command line
works with ACPI too since the efi stub creates a device tree anyway with
the command line.

In KASAN kernels, we can't use the libfdt that early in the boot process
since we are not ready to execute instrumented functions. So instead of
using the "generic" libfdt, we compile our own versions of those functions
that are not instrumented and that are prefixed so that they do not
conflict with the generic ones. We also need the non-instrumented versions
of the string functions and the prefixed versions of memcpy/memmove.

This is largely inspired by commit aacd149b6238 ("arm64: head: avoid
relocating the kernel twice for KASLR") from which I removed compilation
flags that were not relevant to RISC-V at the moment (LTO, SCS, pie).

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Tested-by: Björn Töpel <bjorn@rivosinc.com>
Reviewed-by: Björn Töpel <bjorn@rivosinc.com>

---
 .../admin-guide/kernel-parameters.txt         |  5 +-
 arch/riscv/kernel/Makefile                    |  2 +
 arch/riscv/kernel/pi/Makefile                 | 34 ++++++++++++
 arch/riscv/kernel/pi/cmdline_early.c          | 55 +++++++++++++++++++
 arch/riscv/lib/memcpy.S                       |  2 +
 arch/riscv/lib/memmove.S                      |  2 +
 arch/riscv/mm/init.c                          | 36 ++++++++++--
 7 files changed, 129 insertions(+), 7 deletions(-)
 create mode 100644 arch/riscv/kernel/pi/Makefile
 create mode 100644 arch/riscv/kernel/pi/cmdline_early.c

Comments

kernel test robot Feb. 22, 2023, 3:37 p.m. UTC | #1 
Hi Alexandre,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on linus/master]
[also build test WARNING on v6.2]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Alexandre-Ghiti/riscv-Allow-to-downgrade-paging-mode-from-the-command-line/20230222-184549
patch link:    https://lore.kernel.org/r/20230222104322.1197763-2-alexghiti%40rivosinc.com
patch subject: [PATCH v5 1/1] riscv: Allow to downgrade paging mode from the command line
config: riscv-randconfig-r042-20230222 (https://download.01.org/0day-ci/archive/20230222/202302222359.LdNxjl1c-lkp@intel.com/config)
compiler: clang version 17.0.0 (https://github.com/llvm/llvm-project db89896bbbd2251fff457699635acbbedeead27f)
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # https://github.com/intel-lab-lkp/linux/commit/f92dd2e351d9f51f678f2d7ac63cc3cf85effddd
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Alexandre-Ghiti/riscv-Allow-to-downgrade-paging-mode-from-the-command-line/20230222-184549
        git checkout f92dd2e351d9f51f678f2d7ac63cc3cf85effddd
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash arch/riscv/kernel/pi/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202302222359.LdNxjl1c-lkp@intel.com/

All warnings (new ones prefixed by >>):

>> arch/riscv/kernel/pi/cmdline_early.c:50:12: warning: no previous prototype for function 'set_satp_mode_from_cmdline' [-Wmissing-prototypes]
   u64 __init set_satp_mode_from_cmdline(uintptr_t dtb_pa)
              ^
   arch/riscv/kernel/pi/cmdline_early.c:50:1: note: declare 'static' if the function is not intended to be used outside of this translation unit
   u64 __init set_satp_mode_from_cmdline(uintptr_t dtb_pa)
   ^
   static 
   1 warning generated.


vim +/set_satp_mode_from_cmdline +50 arch/riscv/kernel/pi/cmdline_early.c

    49	
  > 50	u64 __init set_satp_mode_from_cmdline(uintptr_t dtb_pa)
diff mbox series

Patch

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6cfa6e3996cf..1d8fc66d2b0d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3578,7 +3578,10 @@ 
 			emulation library even if a 387 maths coprocessor
 			is present.
 
-	no5lvl		[X86-64] Disable 5-level paging mode. Forces
+	no4lvl		[RISCV] Disable 4-level and 5-level paging modes. Forces
+			kernel to use 3-level paging instead.
+
+	no5lvl		[X86-64,RISCV] Disable 5-level paging mode. Forces
 			kernel to use 4-level paging instead.
 
 	nofsgsbase	[X86] Disables FSGSBASE instructions.
diff --git a/arch/riscv/kernel/Makefile b/arch/riscv/kernel/Makefile
index 4cf303a779ab..6756209f1ac6 100644
--- a/arch/riscv/kernel/Makefile
+++ b/arch/riscv/kernel/Makefile
@@ -89,3 +89,5 @@  obj-$(CONFIG_EFI)		+= efi.o
 obj-$(CONFIG_COMPAT)		+= compat_syscall_table.o
 obj-$(CONFIG_COMPAT)		+= compat_signal.o
 obj-$(CONFIG_COMPAT)		+= compat_vdso/
+
+obj-y				+= pi/
diff --git a/arch/riscv/kernel/pi/Makefile b/arch/riscv/kernel/pi/Makefile
new file mode 100644
index 000000000000..554e936ef0b6
--- /dev/null
+++ b/arch/riscv/kernel/pi/Makefile
@@ -0,0 +1,34 @@ 
+# SPDX-License-Identifier: GPL-2.0
+# This file was copied from arm64/kernel/pi/Makefile.
+
+KBUILD_CFLAGS	:= $(subst $(CC_FLAGS_FTRACE),,$(KBUILD_CFLAGS)) \
+		   -Os -DDISABLE_BRANCH_PROFILING $(DISABLE_STACKLEAK_PLUGIN) \
+		   $(call cc-option,-mbranch-protection=none) \
+		   -I$(srctree)/scripts/dtc/libfdt -fno-stack-protector \
+		   -D__DISABLE_EXPORTS -ffreestanding \
+		   -fno-asynchronous-unwind-tables -fno-unwind-tables \
+		   $(call cc-option,-fno-addrsig)
+
+GCOV_PROFILE	:= n
+KASAN_SANITIZE	:= n
+KCSAN_SANITIZE	:= n
+UBSAN_SANITIZE	:= n
+KCOV_INSTRUMENT	:= n
+
+$(obj)/%.pi.o: OBJCOPYFLAGS := --prefix-symbols=__pi_ \
+			       --remove-section=.note.gnu.property \
+			       --prefix-alloc-sections=.init
+$(obj)/%.pi.o: $(obj)/%.o FORCE
+	$(call if_changed,objcopy)
+
+$(obj)/lib-%.o: $(srctree)/lib/%.c FORCE
+	$(call if_changed_rule,cc_o_c)
+
+$(obj)/string.o: $(srctree)/lib/string.c FORCE
+	$(call if_changed_rule,cc_o_c)
+
+$(obj)/ctype.o: $(srctree)/lib/ctype.c FORCE
+	$(call if_changed_rule,cc_o_c)
+
+obj-y		:= cmdline_early.pi.o string.pi.o ctype.pi.o lib-fdt.pi.o lib-fdt_ro.pi.o
+extra-y		:= $(patsubst %.pi.o,%.o,$(obj-y))
diff --git a/arch/riscv/kernel/pi/cmdline_early.c b/arch/riscv/kernel/pi/cmdline_early.c
new file mode 100644
index 000000000000..be491987d2bf
--- /dev/null
+++ b/arch/riscv/kernel/pi/cmdline_early.c
@@ -0,0 +1,55 @@ 
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/libfdt.h>
+#include <linux/string.h>
+#include <asm/pgtable.h>
+#include <asm/setup.h>
+
+static char early_cmdline[COMMAND_LINE_SIZE] __initdata;
+
+static char * __init get_early_cmdline(uintptr_t dtb_pa)
+{
+	const char *fdt_cmdline = NULL;
+	unsigned int fdt_cmdline_size = 0;
+	int chosen_node;
+
+	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
+		chosen_node = fdt_path_offset((void *)dtb_pa, "/chosen");
+		if (chosen_node >= 0) {
+			fdt_cmdline = fdt_getprop((void *)dtb_pa, chosen_node,
+						  "bootargs", NULL);
+			if (fdt_cmdline) {
+				fdt_cmdline_size = strlen(fdt_cmdline);
+				strscpy(early_cmdline, fdt_cmdline,
+					COMMAND_LINE_SIZE);
+			}
+		}
+	}
+
+	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
+	    IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
+	    fdt_cmdline_size == 0 /* CONFIG_CMDLINE_FALLBACK */) {
+		strncat(early_cmdline, CONFIG_CMDLINE,
+			COMMAND_LINE_SIZE - fdt_cmdline_size);
+	}
+
+	return early_cmdline;
+}
+
+static u64 __init match_noXlvl(char *cmdline)
+{
+	if (strstr(cmdline, "no4lvl"))
+		return SATP_MODE_48;
+	else if (strstr(cmdline, "no5lvl"))
+		return SATP_MODE_57;
+
+	return 0;
+}
+
+u64 __init set_satp_mode_from_cmdline(uintptr_t dtb_pa)
+{
+	char *cmdline = get_early_cmdline(dtb_pa);
+
+	return match_noXlvl(cmdline);
+}
diff --git a/arch/riscv/lib/memcpy.S b/arch/riscv/lib/memcpy.S
index 51ab716253fa..1a40d01a9543 100644
--- a/arch/riscv/lib/memcpy.S
+++ b/arch/riscv/lib/memcpy.S
@@ -106,3 +106,5 @@  WEAK(memcpy)
 6:
 	ret
 END(__memcpy)
+SYM_FUNC_ALIAS(__pi_memcpy, __memcpy)
+SYM_FUNC_ALIAS(__pi___memcpy, __memcpy)
diff --git a/arch/riscv/lib/memmove.S b/arch/riscv/lib/memmove.S
index e0609e1f0864..838ff2022fe3 100644
--- a/arch/riscv/lib/memmove.S
+++ b/arch/riscv/lib/memmove.S
@@ -314,3 +314,5 @@  return_from_memmove:
 
 SYM_FUNC_END(memmove)
 SYM_FUNC_END(__memmove)
+SYM_FUNC_ALIAS(__pi_memmove, __memmove)
+SYM_FUNC_ALIAS(__pi___memmove, __memmove)
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 87f6a5d475a6..04d20e41894e 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -732,6 +732,8 @@  static __init pgprot_t pgprot_from_va(uintptr_t va)
 #endif /* CONFIG_STRICT_KERNEL_RWX */
 
 #if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
+u64 __pi_set_satp_mode_from_cmdline(uintptr_t dtb_pa);
+
 static void __init disable_pgtable_l5(void)
 {
 	pgtable_l5_enabled = false;
@@ -746,17 +748,39 @@  static void __init disable_pgtable_l4(void)
 	satp_mode = SATP_MODE_39;
 }
 
+static int __init print_no4lvl(char *p)
+{
+	pr_info("Disabled 4-level and 5-level paging");
+	return 0;
+}
+early_param("no4lvl", print_no4lvl);
+
+static int __init print_no5lvl(char *p)
+{
+	pr_info("Disabled 5-level paging");
+	return 0;
+}
+early_param("no5lvl", print_no5lvl);
+
 /*
  * There is a simple way to determine if 4-level is supported by the
  * underlying hardware: establish 1:1 mapping in 4-level page table mode
  * then read SATP to see if the configuration was taken into account
  * meaning sv48 is supported.
  */
-static __init void set_satp_mode(void)
+static __init void set_satp_mode(uintptr_t dtb_pa)
 {
 	u64 identity_satp, hw_satp;
 	uintptr_t set_satp_mode_pmd = ((unsigned long)set_satp_mode) & PMD_MASK;
-	bool check_l4 = false;
+	u64 satp_mode_cmdline = __pi_set_satp_mode_from_cmdline(dtb_pa);
+
+	if (satp_mode_cmdline == SATP_MODE_57) {
+		disable_pgtable_l5();
+	} else if (satp_mode_cmdline == SATP_MODE_48) {
+		disable_pgtable_l5();
+		disable_pgtable_l4();
+		return;
+	}
 
 	create_p4d_mapping(early_p4d,
 			set_satp_mode_pmd, (uintptr_t)early_pud,
@@ -775,7 +799,8 @@  static __init void set_satp_mode(void)
 retry:
 	create_pgd_mapping(early_pg_dir,
 			   set_satp_mode_pmd,
-			   check_l4 ? (uintptr_t)early_pud : (uintptr_t)early_p4d,
+			   pgtable_l5_enabled ?
+				(uintptr_t)early_p4d : (uintptr_t)early_pud,
 			   PGDIR_SIZE, PAGE_TABLE);
 
 	identity_satp = PFN_DOWN((uintptr_t)&early_pg_dir) | satp_mode;
@@ -786,9 +811,8 @@  static __init void set_satp_mode(void)
 	local_flush_tlb_all();
 
 	if (hw_satp != identity_satp) {
-		if (!check_l4) {
+		if (pgtable_l5_enabled) {
 			disable_pgtable_l5();
-			check_l4 = true;
 			memset(early_pg_dir, 0, PAGE_SIZE);
 			goto retry;
 		}
@@ -979,7 +1003,7 @@  asmlinkage void __init setup_vm(uintptr_t dtb_pa)
 #endif
 
 #if defined(CONFIG_64BIT) && !defined(CONFIG_XIP_KERNEL)
-	set_satp_mode();
+	set_satp_mode(dtb_pa);
 #endif
 
 	kernel_map.va_pa_offset = PAGE_OFFSET - kernel_map.phys_addr;