[PATCH] arm64: relocate-rela: Add support for ld.lld

Alistair Delva
2021-10-20T21:40:51Z

Cap end of relocations by the binary size.

Linkers like to insert some auxiliary sections between .rela.dyn and
.bss_start. These sections don't make their way to the final binary, but
reloc_rela still tries to relocate them, resulting in attempted read
past the end of file.

When linking U-Boot with ld.lld, the STATIC_RELA feature (enabled by
default on arm64) breaks the build. After this patch, U-Boot can be
linked successfully with and without CONFIG_STATIC_RELA.

Originally-from: Elena Petrova <lenaptr@google.com>
Signed-off-by: Alistair Delva <adelva@google.com>
Cc: David Brazdil <dbrazdil@google.com>
Cc: Scott Wood <scottwood@freescale.com>
Cc: Tom Rini <trini@konsulko.com>
---
tools/relocate-rela.c | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/tools/relocate-rela.c b/tools/relocate-rela.c
index 6a524014b7..f0bc548617 100644
--- a/tools/relocate-rela.c
+++ b/tools/relocate-rela.c
@@ -63,7 +63,7 @@ int main(int argc, char **argv)
{
FILE *f;
int i, num;
- uint64_t rela_start, rela_end, text_base;
+ uint64_t rela_start, rela_end, text_base, file_size;

if (argc != 5) {
fprintf(stderr, "Statically apply ELF rela relocations\n");
@@ -87,8 +87,7 @@ int main(int argc, char **argv)
return 3;
}

- if (rela_start > rela_end || rela_start < text_base ||
- (rela_end - rela_start) % sizeof(Elf64_Rela)) {
+ if (rela_start > rela_end || rela_start < text_base) {
fprintf(stderr, "%s: bad rela bounds\n", argv[0]);
return 3;
}
@@ -96,6 +95,21 @@ int main(int argc, char **argv)
rela_start -= text_base;
rela_end -= text_base;

+ fseek(f, 0, SEEK_END);
+ file_size = ftell(f);
+ rewind(f);
+
+ if (rela_end > file_size) {
+ // Most likely compiler inserted some section that didn't get
+ // objcopy-ed into the final binary
+ rela_end = file_size;
+ }
+
+ if ((rela_end - rela_start) % sizeof(Elf64_Rela)) {
+ fprintf(stderr, "%s: rela size isn't a multiple of Elf64_Rela\n", argv[0]);
+ return 3;
+ }
+
num = (rela_end - rela_start) / sizeof(Elf64_Rela);

for (i = 0; i < num; i++) {
--
2.30.2