[Crash-utility PATCH] RISCV64: Add KASLR support

[Song Shuai]

From: Song Shuai <suagrfillet at gmail.com>

This patch adds KASLR support for Crash to analyze KASLR-ed vmcore
since RISC-V Linux is already sufficiently prepared for KASLR [1].

With this patch, even if the Crash '--kaslr' option is not set or Linux
CONFIG_RANDOMIZE_BASE is not configured, the 'derive_kaslr_offset()'
function will always work to calculate 'kt->relocate' which serves to
update the kernel virtual address.

[1]: https://lore.kernel.org/linux-riscv/20230722123850.634544-1-alexghiti@rivosinc.com/

Signed-off-by: Song Shuai <suagrfillet at gmail.com>
---
 main.c    |  2 +-
 riscv64.c | 11 +++++++++++
 symbols.c |  4 ++--
 3 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/main.c b/main.c
index b278c22..0c6e595 100644
--- a/main.c
+++ b/main.c
@@ -228,7 +228,7 @@ main(int argc, char **argv)
 			} else if (STREQ(long_options[option_index].name, "kaslr")) {
 				if (!machine_type("X86_64") &&
 				    !machine_type("ARM64") && !machine_type("X86") &&
-				    !machine_type("S390X"))
+				    !machine_type("S390X") && !machine_type("RISCV64"))
 					error(INFO, "--kaslr not valid "
 						"with this machine type.\n");
 				else if (STREQ(optarg, "auto"))
diff --git a/riscv64.c b/riscv64.c
index a02f75a..288c7ae 100644
--- a/riscv64.c
+++ b/riscv64.c
@@ -378,6 +378,9 @@ static void riscv64_get_va_range(struct machine_specific *ms)
 	} else
 		goto error;
 
+	if ((kt->flags2 & KASLR) && (kt->flags & RELOC_SET))
+		ms->kernel_link_addr += (kt->relocate * -1);
+
 	/*
 	 * From Linux 5.13, the kernel mapping is moved to the last 2GB
 	 * of the address space, modules use the 2GB memory range right
@@ -1360,6 +1363,14 @@ riscv64_init(int when)
 
 		machdep->verify_paddr = generic_verify_paddr;
 		machdep->ptrs_per_pgd = PTRS_PER_PGD;
+
+		/*
+		 * Even if CONFIG_RANDOMIZE_BASE is not configured,
+		 * derive_kaslr_offset() should work and set
+		 * kt->relocate to 0
+		 */
+		if (!kt->relocate && !(kt->flags2 & (RELOC_AUTO|KASLR)))
+			kt->flags2 |= (RELOC_AUTO|KASLR);
 		break;
 
 	case PRE_GDB:
diff --git a/symbols.c b/symbols.c
index 876be7a..8e8b4c3 100644
--- a/symbols.c
+++ b/symbols.c
@@ -629,7 +629,7 @@ kaslr_init(void)
 	char *string;
 
 	if ((!machine_type("X86_64") && !machine_type("ARM64") && !machine_type("X86") &&
-	    !machine_type("S390X")) || (kt->flags & RELOC_SET))
+	    !machine_type("S390X") && !machine_type("RISCV64")) || (kt->flags & RELOC_SET))
 		return;
 
 	if (!kt->vmcoreinfo._stext_SYMBOL &&
@@ -795,7 +795,7 @@ store_symbols(bfd *abfd, int dynamic, void *minisyms, long symcount,
 		} else if (!(kt->flags & RELOC_SET))
 			kt->flags |= RELOC_FORCE;
 	} else if (machine_type("X86_64") || machine_type("ARM64") ||
-		   machine_type("S390X")) {
+		   machine_type("S390X") || machine_type("RISCV64")) {
 		if ((kt->flags2 & RELOC_AUTO) && !(kt->flags & RELOC_SET))
 			derive_kaslr_offset(abfd, dynamic, from,
 				fromend, size, store);
-- 
2.20.1