[PATCH kernel v4] powerpc/64: Add UADDR64 relocation support
flat view
STALE1673d
LANDED
From: Alexey Kardashevskiy <hidden>
Date: 2022-03-09 06:18:57
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Linus Torvalds
Landed in mainline as d79976918852 on 2022-03-09.
When ld detects unaligned relocations, it emits R_PPC64_UADDR64
relocations instead of R_PPC64_RELATIVE. Currently R_PPC64_UADDR64 are
detected by arch/powerpc/tools/relocs_check.sh and expected not to work.
Below is a simple chunk to trigger this behaviour (this disables
optimization for the demonstration purposes only, this also happens with
-O1/-O2 when CONFIG_PRINTK_INDEX=y, for example):
\#pragma GCC push_options
\#pragma GCC optimize ("O0")
struct entry {
const char *file;
int line;
} __attribute__((packed));
static const struct entry e1 = { .file = __FILE__, .line = __LINE__ };
static const struct entry e2 = { .file = __FILE__, .line = __LINE__ };
...
prom_printf("e1=%s %lx %lx\n", e1.file, (unsigned long) e1.file, mfmsr());
prom_printf("e2=%s %lx\n", e2.file, (unsigned long) e2.file);
\#pragma GCC pop_options
This adds support for UADDR64 for 64bit. This reuses __dynamic_symtab
from the 32bit which supports more relocation types already.
Because RELACOUNT includes only R_PPC64_RELATIVE, this replaces it with
RELASZ which is the size of all relocation records.
Signed-off-by: Alexey Kardashevskiy <redacted>
---
Changes:
v4:
* fixed reloc->r_info hadling on big endian
v3:
* named some labels
v2:
* replaced RELACOUNT with RELASZ/RELAENT
* removed FIXME
---
arch/powerpc/kernel/reloc_64.S | 67 +++++++++++++++++++++---------
arch/powerpc/kernel/vmlinux.lds.S | 2 -
arch/powerpc/tools/relocs_check.sh | 7 +---
3 files changed, 48 insertions(+), 28 deletions(-)
diff --git a/arch/powerpc/kernel/reloc_64.S b/arch/powerpc/kernel/reloc_64.S
index 02d4719bf43a..232e4549defe 100644
--- a/arch/powerpc/kernel/reloc_64.S
+++ b/arch/powerpc/kernel/reloc_64.S@@ -8,8 +8,10 @@ #include <asm/ppc_asm.h> RELA = 7 -RELACOUNT = 0x6ffffff9 +RELASZ = 8 +RELAENT = 9 R_PPC64_RELATIVE = 22 +R_PPC64_UADDR64 = 43 /* * r3 = desired final address of kernel
@@ -25,29 +27,38 @@ _GLOBAL(relocate) add r9,r9,r12 /* r9 has runtime addr of .rela.dyn section */ ld r10,(p_st - 0b)(r12) add r10,r10,r12 /* r10 has runtime addr of _stext */ + ld r13,(p_sym - 0b)(r12) + add r13,r13,r12 /* r13 has runtime addr of .dynsym */ /* - * Scan the dynamic section for the RELA and RELACOUNT entries. + * Scan the dynamic section for the RELA, RELASZ and RELAENT entries. */ li r7,0 li r8,0 -1: ld r6,0(r11) /* get tag */ +.Ltags: + ld r6,0(r11) /* get tag */ cmpdi r6,0 - beq 4f /* end of list */ + beq .Lend_of_list /* end of list */ cmpdi r6,RELA bne 2f ld r7,8(r11) /* get RELA pointer in r7 */ - b 3f -2: addis r6,r6,(-RELACOUNT)@ha - cmpdi r6,RELACOUNT@l + b 4f +2: cmpdi r6,RELASZ bne 3f - ld r8,8(r11) /* get RELACOUNT value in r8 */ -3: addi r11,r11,16 - b 1b -4: cmpdi r7,0 /* check we have both RELA and RELACOUNT */ + ld r8,8(r11) /* get RELASZ value in r8 */ + b 4f +3: cmpdi r6,RELAENT + bne 4f + ld r12,8(r11) /* get RELAENT value in r12 */ +4: addi r11,r11,16 + b .Ltags +.Lend_of_list: + cmpdi r7,0 /* check we have RELA, RELASZ, RELAENT */ cmpdi cr1,r8,0 - beq 6f - beq cr1,6f + beq .Lout + beq cr1,.Lout + cmpdi r12,0 + beq .Lout /* * Work out linktime address of _stext and hence the
@@ -62,23 +73,39 @@ _GLOBAL(relocate) /* * Run through the list of relocations and process the - * R_PPC64_RELATIVE ones. + * R_PPC64_RELATIVE and R_PPC64_UADDR64 ones. */ + divd r8,r8,r12 /* RELASZ / RELAENT */ mtctr r8 -5: ld r0,8(9) /* ELF64_R_TYPE(reloc->r_info) */ +.Lrels: ld r0,8(r9) /* ELF64_R_TYPE(reloc->r_info) */ cmpdi r0,R_PPC64_RELATIVE - bne 6f + bne .Luaddr64 ld r6,0(r9) /* reloc->r_offset */ ld r0,16(r9) /* reloc->r_addend */ + b .Lstore +.Luaddr64: + srdi r14,r0,32 /* ELF64_R_SYM(reloc->r_info) */ + clrldi r0,r0,32 + cmpdi r0,R_PPC64_UADDR64 + bne .Lnext + ld r6,0(r9) + ld r0,16(r9) + mulli r14,r14,24 /* 24 == sizeof(elf64_sym) */ + add r14,r14,r13 /* elf64_sym[ELF64_R_SYM] */ + ld r14,8(r14) + add r0,r0,r14 +.Lstore: add r0,r0,r3 stdx r0,r7,r6 - addi r9,r9,24 - bdnz 5b - -6: blr +.Lnext: + add r9,r9,r12 + bdnz .Lrels +.Lout: + blr .balign 8 p_dyn: .8byte __dynamic_start - 0b p_rela: .8byte __rela_dyn_start - 0b +p_sym: .8byte __dynamic_symtab - 0b p_st: .8byte _stext - 0b
diff --git a/arch/powerpc/kernel/vmlinux.lds.S b/arch/powerpc/kernel/vmlinux.lds.S
index 2bcca818136a..fe22d940412f 100644
--- a/arch/powerpc/kernel/vmlinux.lds.S
+++ b/arch/powerpc/kernel/vmlinux.lds.S@@ -281,9 +281,7 @@ SECTIONS . = ALIGN(8); .dynsym : AT(ADDR(.dynsym) - LOAD_OFFSET) { -#ifdef CONFIG_PPC32 __dynamic_symtab = .; -#endif *(.dynsym) } .dynstr : AT(ADDR(.dynstr) - LOAD_OFFSET) { *(.dynstr) }
diff --git a/arch/powerpc/tools/relocs_check.sh b/arch/powerpc/tools/relocs_check.sh
index 014e00e74d2b..63792af00417 100755
--- a/arch/powerpc/tools/relocs_check.sh
+++ b/arch/powerpc/tools/relocs_check.sh@@ -39,6 +39,7 @@ $objdump -R "$vmlinux" | # R_PPC_NONE grep -F -w -v 'R_PPC64_RELATIVE R_PPC64_NONE +R_PPC64_UADDR64 R_PPC_ADDR16_LO R_PPC_ADDR16_HI R_PPC_ADDR16_HA
@@ -54,9 +55,3 @@ fi num_bad=$(echo "$bad_relocs" | wc -l) echo "WARNING: $num_bad bad relocations" echo "$bad_relocs" - -# If we see this type of relocation it's an idication that -# we /may/ be using an old version of binutils. -if echo "$bad_relocs" | grep -q -F -w R_PPC64_UADDR64; then - echo "WARNING: You need at least binutils >= 2.19 to build a CONFIG_RELOCATABLE kernel" -fi
--
2.30.2