Commit d7997691 authored by Alexey Kardashevskiy's avatar Alexey Kardashevskiy Committed by Michael Ellerman

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: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220309061822.168173-1-aik@ozlabs.ru
parent 3fd46e55
......@@ -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
......@@ -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) }
......
......@@ -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
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