1 files changed, 130 insertions, 0 deletions
diff --git a/arch/arm64/kernel/pi/relacheck.c b/arch/arm64/kernel/pi/relacheck.c
new file mode 100644
index 0000000000..b0cd4d0d27
--- /dev/null
+++ b/arch/arm64/kernel/pi/relacheck.c
@@ -0,0 +1,130 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2023 - Google LLC
+ * Author: Ard Biesheuvel <ardb@google.com>
+ */
+
+#include <elf.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define HOST_ORDER ELFDATA2LSB
+#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+#define HOST_ORDER ELFDATA2MSB
+#endif
+
+static Elf64_Ehdr *ehdr;
+static Elf64_Shdr *shdr;
+static const char *strtab;
+static bool swap;
+
+static uint64_t swab_elfxword(uint64_t val)
+{
+	return swap ? __builtin_bswap64(val) : val;
+}
+
+static uint32_t swab_elfword(uint32_t val)
+{
+	return swap ? __builtin_bswap32(val) : val;
+}
+
+static uint16_t swab_elfhword(uint16_t val)
+{
+	return swap ? __builtin_bswap16(val) : val;
+}
+
+int main(int argc, char *argv[])
+{
+	struct stat stat;
+	int fd, ret;
+
+	if (argc < 3) {
+		fprintf(stderr, "file arguments missing\n");
+		exit(EXIT_FAILURE);
+	}
+
+	fd = open(argv[1], O_RDWR);
+	if (fd < 0) {
+		fprintf(stderr, "failed to open %s\n", argv[1]);
+		exit(EXIT_FAILURE);
+	}
+
+	ret = fstat(fd, &stat);
+	if (ret < 0) {
+		fprintf(stderr, "failed to stat() %s\n", argv[1]);
+		exit(EXIT_FAILURE);
+	}
+
+	ehdr = mmap(0, stat.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (ehdr == MAP_FAILED) {
+		fprintf(stderr, "failed to mmap() %s\n", argv[1]);
+		exit(EXIT_FAILURE);
+	}
+
+	swap = ehdr->e_ident[EI_DATA] != HOST_ORDER;
+	shdr = (void *)ehdr + swab_elfxword(ehdr->e_shoff);
+	strtab = (void *)ehdr +
+		 swab_elfxword(shdr[swab_elfhword(ehdr->e_shstrndx)].sh_offset);
+
+	for (int i = 0; i < swab_elfhword(ehdr->e_shnum); i++) {
+		unsigned long info, flags;
+		bool prel64 = false;
+		Elf64_Rela *rela;
+		int numrela;
+
+		if (swab_elfword(shdr[i].sh_type) != SHT_RELA)
+			continue;
+
+		/* only consider RELA sections operating on data */
+		info = swab_elfword(shdr[i].sh_info);
+		flags = swab_elfxword(shdr[info].sh_flags);
+		if ((flags & (SHF_ALLOC | SHF_EXECINSTR)) != SHF_ALLOC)
+			continue;
+
+		/*
+		 * We generally don't permit ABS64 relocations in the code that
+		 * runs before relocation processing occurs. If statically
+		 * initialized absolute symbol references are unavoidable, they
+		 * may be emitted into a *.rodata.prel64 section and they will
+		 * be converted to place-relative 64-bit references. This
+		 * requires special handling in the referring code.
+		 */
+		if (strstr(strtab + swab_elfword(shdr[info].sh_name),
+			   ".rodata.prel64")) {
+			prel64 = true;
+		}
+
+		rela = (void *)ehdr + swab_elfxword(shdr[i].sh_offset);
+		numrela = swab_elfxword(shdr[i].sh_size) / sizeof(*rela);
+
+		for (int j = 0; j < numrela; j++) {
+			uint64_t info = swab_elfxword(rela[j].r_info);
+
+			if (ELF64_R_TYPE(info) != R_AARCH64_ABS64)
+				continue;
+
+			if (prel64) {
+				/* convert ABS64 into PREL64 */
+				info ^= R_AARCH64_ABS64 ^ R_AARCH64_PREL64;
+				rela[j].r_info = swab_elfxword(info);
+			} else {
+				fprintf(stderr,
+					"Unexpected absolute relocations detected in %s\n",
+					argv[2]);
+				close(fd);
+				unlink(argv[1]);
+				exit(EXIT_FAILURE);
+			}
+		}
+	}
+	close(fd);
+	return 0;
+}