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authorXi Ruoyao <xry111@xry111.site>2024-07-20 22:41:07 +0800
committerHuacai Chen <chenhuacai@loongson.cn>2024-07-20 22:41:07 +0800
commite05d4cd9b895c503dcf19c0ed9ebb8d393b220ec (patch)
treed2dd552b4b7288dcf43bc79084d884e907c7de95 /arch
parent0ad158e4ef769c5f261cbf791e0005d69fc3b785 (diff)
LoongArch: Add support for relocating the kernel with RELR relocation
RELR as a relocation packing format for relative relocations for reducing the size of relative relocation records. In a position independent executable there are often many relative relocation records, and our vmlinux is a PIE. The LLD linker (since 17.0.0) and the BFD linker (since 2.43) supports packing the relocations in the RELR format for LoongArch, with the flag -z pack-relative-relocs. Commits 5cf896fb6be3eff ("arm64: Add support for relocating the kernel with RELR relocations") and ccb2d173b983984bfa ("Makefile: use -z pack-relative-relocs") have already added the framework to use RELR. We just need to wire it up and process the RELR relocation records in relocate_relative() in addition to the RELA relocation records. A ".p2align 3" directive is added to la_abs macro or the BFD linker cannot pack the relocation records against the .la_abs section (the ". = ALIGN(8);" directive in vmlinux.lds.S is too late in the linking process). With defconfig and CONFIG_RELR vmlinux.efi is 2.1 MiB (6%) smaller, and vmlinuz.efi (using gzip compression) is 384 KiB (2.8%) smaller. Link: https://groups.google.com/d/topic/generic-abi/bX460iggiKg Link: https://reviews.llvm.org/D138135#4531389 Link: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=d89ecf33ab6d Signed-off-by: Xi Ruoyao <xry111@xry111.site> Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
Diffstat (limited to 'arch')
-rw-r--r--arch/loongarch/Kconfig1
-rw-r--r--arch/loongarch/include/asm/asmmacro.h1
-rw-r--r--arch/loongarch/include/asm/setup.h5
-rw-r--r--arch/loongarch/kernel/relocate.c18
-rw-r--r--arch/loongarch/kernel/vmlinux.lds.S8
5 files changed, 33 insertions, 0 deletions
diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 9687b1d24126..f5df69ad70a6 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -610,6 +610,7 @@ config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
config RELOCATABLE
bool "Relocatable kernel"
+ select ARCH_HAS_RELR
help
This builds the kernel as a Position Independent Executable (PIE),
which retains all relocation metadata required, so as to relocate
diff --git a/arch/loongarch/include/asm/asmmacro.h b/arch/loongarch/include/asm/asmmacro.h
index 655db7d7a427..8d7f501b0a12 100644
--- a/arch/loongarch/include/asm/asmmacro.h
+++ b/arch/loongarch/include/asm/asmmacro.h
@@ -609,6 +609,7 @@
lu32i.d \reg, 0
lu52i.d \reg, \reg, 0
.pushsection ".la_abs", "aw", %progbits
+ .p2align 3
.dword 766b
.dword \sym
.popsection
diff --git a/arch/loongarch/include/asm/setup.h b/arch/loongarch/include/asm/setup.h
index ee52fb1e9963..3c2fb16b11b6 100644
--- a/arch/loongarch/include/asm/setup.h
+++ b/arch/loongarch/include/asm/setup.h
@@ -34,6 +34,11 @@ extern long __la_abs_end;
extern long __rela_dyn_begin;
extern long __rela_dyn_end;
+#ifdef CONFIG_RELR
+extern long __relr_dyn_begin;
+extern long __relr_dyn_end;
+#endif
+
extern unsigned long __init relocate_kernel(void);
#endif
diff --git a/arch/loongarch/kernel/relocate.c b/arch/loongarch/kernel/relocate.c
index e3836f0b9bd8..50c469067f3a 100644
--- a/arch/loongarch/kernel/relocate.c
+++ b/arch/loongarch/kernel/relocate.c
@@ -38,6 +38,24 @@ static inline void __init relocate_relative(void)
relocated_addr = (Elf64_Addr)RELOCATED(relocated_addr);
*(Elf64_Addr *)RELOCATED(addr) = relocated_addr;
}
+
+#ifdef CONFIG_RELR
+ u64 *addr = NULL;
+ u64 *relr = (u64 *)&__relr_dyn_begin;
+ u64 *relr_end = (u64 *)&__relr_dyn_end;
+
+ for ( ; relr < relr_end; relr++) {
+ if ((*relr & 1) == 0) {
+ addr = (u64 *)(*relr + reloc_offset);
+ *addr++ += reloc_offset;
+ } else {
+ for (u64 *p = addr, r = *relr >> 1; r; p++, r >>= 1)
+ if (r & 1)
+ *p += reloc_offset;
+ addr += 63;
+ }
+ }
+#endif
}
static inline void __init relocate_absolute(long random_offset)
diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
index 3c7595342730..08ea921cdec1 100644
--- a/arch/loongarch/kernel/vmlinux.lds.S
+++ b/arch/loongarch/kernel/vmlinux.lds.S
@@ -113,6 +113,14 @@ SECTIONS
__rela_dyn_end = .;
}
+#ifdef CONFIG_RELR
+ .relr.dyn : ALIGN(8) {
+ __relr_dyn_begin = .;
+ *(.relr.dyn)
+ __relr_dyn_end = .;
+ }
+#endif
+
.data.rel : { *(.data.rel*) }
#ifdef CONFIG_RELOCATABLE