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powerpc/64: Add UADDR64 relocation support
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 code 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 <aik@ozlabs.ru>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220309061822.168173-1-aik@ozlabs.ru
This commit is contained in:
Alexey Kardashevskiy
Michael Ellerman
parent
3fd46e551f
commit
d799769188
3 changed files with 48 additions and 28 deletions
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@ -8,8 +8,10 @@
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#include <asm/ppc_asm.h>
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RELA = 7
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RELACOUNT = 0x6ffffff9
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RELASZ = 8
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RELAENT = 9
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R_PPC64_RELATIVE = 22
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R_PPC64_UADDR64 = 43
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/*
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* r3 = desired final address of kernel
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@ -25,29 +27,38 @@ _GLOBAL(relocate)
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add r9,r9,r12 /* r9 has runtime addr of .rela.dyn section */
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ld r10,(p_st - 0b)(r12)
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add r10,r10,r12 /* r10 has runtime addr of _stext */
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ld r13,(p_sym - 0b)(r12)
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add r13,r13,r12 /* r13 has runtime addr of .dynsym */
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/*
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* Scan the dynamic section for the RELA and RELACOUNT entries.
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* Scan the dynamic section for the RELA, RELASZ and RELAENT entries.
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*/
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li r7,0
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li r8,0
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1: ld r6,0(r11) /* get tag */
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.Ltags:
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ld r6,0(r11) /* get tag */
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cmpdi r6,0
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beq 4f /* end of list */
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beq .Lend_of_list /* end of list */
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cmpdi r6,RELA
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bne 2f
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ld r7,8(r11) /* get RELA pointer in r7 */
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b 3f
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2: addis r6,r6,(-RELACOUNT)@ha
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cmpdi r6,RELACOUNT@l
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b 4f
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2: cmpdi r6,RELASZ
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bne 3f
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ld r8,8(r11) /* get RELACOUNT value in r8 */
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3: addi r11,r11,16
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b 1b
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4: cmpdi r7,0 /* check we have both RELA and RELACOUNT */
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ld r8,8(r11) /* get RELASZ value in r8 */
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b 4f
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3: cmpdi r6,RELAENT
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bne 4f
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ld r12,8(r11) /* get RELAENT value in r12 */
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4: addi r11,r11,16
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b .Ltags
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.Lend_of_list:
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cmpdi r7,0 /* check we have RELA, RELASZ, RELAENT */
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cmpdi cr1,r8,0
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beq 6f
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beq cr1,6f
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beq .Lout
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beq cr1,.Lout
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cmpdi r12,0
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beq .Lout
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/*
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* Work out linktime address of _stext and hence the
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@ -62,23 +73,39 @@ _GLOBAL(relocate)
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/*
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* Run through the list of relocations and process the
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* R_PPC64_RELATIVE ones.
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* R_PPC64_RELATIVE and R_PPC64_UADDR64 ones.
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*/
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divd r8,r8,r12 /* RELASZ / RELAENT */
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mtctr r8
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5: ld r0,8(9) /* ELF64_R_TYPE(reloc->r_info) */
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.Lrels: ld r0,8(r9) /* ELF64_R_TYPE(reloc->r_info) */
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cmpdi r0,R_PPC64_RELATIVE
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bne 6f
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bne .Luaddr64
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ld r6,0(r9) /* reloc->r_offset */
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ld r0,16(r9) /* reloc->r_addend */
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b .Lstore
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.Luaddr64:
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srdi r14,r0,32 /* ELF64_R_SYM(reloc->r_info) */
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clrldi r0,r0,32
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cmpdi r0,R_PPC64_UADDR64
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bne .Lnext
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ld r6,0(r9)
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ld r0,16(r9)
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mulli r14,r14,24 /* 24 == sizeof(elf64_sym) */
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add r14,r14,r13 /* elf64_sym[ELF64_R_SYM] */
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ld r14,8(r14)
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add r0,r0,r14
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.Lstore:
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add r0,r0,r3
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stdx r0,r7,r6
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addi r9,r9,24
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bdnz 5b
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6: blr
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.Lnext:
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add r9,r9,r12
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bdnz .Lrels
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.Lout:
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blr
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.balign 8
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p_dyn: .8byte __dynamic_start - 0b
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p_rela: .8byte __rela_dyn_start - 0b
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p_sym: .8byte __dynamic_symtab - 0b
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p_st: .8byte _stext - 0b
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@ -281,9 +281,7 @@ SECTIONS
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. = ALIGN(8);
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.dynsym : AT(ADDR(.dynsym) - LOAD_OFFSET)
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{
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#ifdef CONFIG_PPC32
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__dynamic_symtab = .;
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#endif
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*(.dynsym)
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}
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.dynstr : AT(ADDR(.dynstr) - LOAD_OFFSET) { *(.dynstr) }
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@ -39,6 +39,7 @@ $objdump -R "$vmlinux" |
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# R_PPC_NONE
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grep -F -w -v 'R_PPC64_RELATIVE
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R_PPC64_NONE
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R_PPC64_UADDR64
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R_PPC_ADDR16_LO
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R_PPC_ADDR16_HI
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R_PPC_ADDR16_HA
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@ -54,9 +55,3 @@ fi
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num_bad=$(echo "$bad_relocs" | wc -l)
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echo "WARNING: $num_bad bad relocations"
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echo "$bad_relocs"
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# If we see this type of relocation it's an idication that
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# we /may/ be using an old version of binutils.
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if echo "$bad_relocs" | grep -q -F -w R_PPC64_UADDR64; then
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echo "WARNING: You need at least binutils >= 2.19 to build a CONFIG_RELOCATABLE kernel"
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fi
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