Commit c14d31ba authored by Alexey Kardashevskiy's avatar Alexey Kardashevskiy Committed by Michael Ellerman

powerpc/boot: Stop using RELACOUNT

So far the RELACOUNT tag from the ELF header was containing the exact
number of R_PPC_RELATIVE/R_PPC64_RELATIVE relocations. However the LLVM's
recent change [1] make it equal-or-less than the actual number which
makes it useless.

This replaces RELACOUNT in zImage loader with a pair of RELASZ and RELAENT.
The vmlinux relocation code is fixed in commit d7997691
("powerpc/64: Add UADDR64 relocation support").

To make it more future proof, this walks through the entire .rela.dyn
section instead of assuming that the section is sorter by a relocation
type. Unlike d7997691, this does not add unaligned UADDR/UADDR64
relocations as we are likely not to see those in practice - the zImage
is small and very arch specific so there is a smaller chance that some
generic feature (such as PRINK_INDEX) triggers unaligned relocations.

[1] https://github.com/llvm/llvm-project/commit/da0e5b885b25cf4Signed-off-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220406070038.3704604-1-aik@ozlabs.ru
parent 3ba4289a
...@@ -8,7 +8,8 @@ ...@@ -8,7 +8,8 @@
#include "ppc_asm.h" #include "ppc_asm.h"
RELA = 7 RELA = 7
RELACOUNT = 0x6ffffff9 RELASZ = 8
RELAENT = 9
.data .data
/* A procedure descriptor used when booting this as a COFF file. /* A procedure descriptor used when booting this as a COFF file.
...@@ -75,34 +76,39 @@ p_base: mflr r10 /* r10 now points to runtime addr of p_base */ ...@@ -75,34 +76,39 @@ p_base: mflr r10 /* r10 now points to runtime addr of p_base */
bne 11f bne 11f
lwz r9,4(r12) /* get RELA pointer in r9 */ lwz r9,4(r12) /* get RELA pointer in r9 */
b 12f b 12f
11: addis r8,r8,(-RELACOUNT)@ha 11: cmpwi r8,RELASZ
cmpwi r8,RELACOUNT@l bne .Lcheck_for_relaent
lwz r0,4(r12) /* get RELASZ value in r0 */
b 12f
.Lcheck_for_relaent:
cmpwi r8,RELAENT
bne 12f bne 12f
lwz r0,4(r12) /* get RELACOUNT value in r0 */ lwz r14,4(r12) /* get RELAENT value in r14 */
12: addi r12,r12,8 12: addi r12,r12,8
b 9b b 9b
/* The relocation section contains a list of relocations. /* The relocation section contains a list of relocations.
* We now do the R_PPC_RELATIVE ones, which point to words * We now do the R_PPC_RELATIVE ones, which point to words
* which need to be initialized with addend + offset. * which need to be initialized with addend + offset */
* The R_PPC_RELATIVE ones come first and there are RELACOUNT
* of them. */
10: /* skip relocation if we don't have both */ 10: /* skip relocation if we don't have both */
cmpwi r0,0 cmpwi r0,0
beq 3f beq 3f
cmpwi r9,0 cmpwi r9,0
beq 3f beq 3f
cmpwi r14,0
beq 3f
add r9,r9,r11 /* Relocate RELA pointer */ add r9,r9,r11 /* Relocate RELA pointer */
divwu r0,r0,r14 /* RELASZ / RELAENT */
mtctr r0 mtctr r0
2: lbz r0,4+3(r9) /* ELF32_R_INFO(reloc->r_info) */ 2: lbz r0,4+3(r9) /* ELF32_R_INFO(reloc->r_info) */
cmpwi r0,22 /* R_PPC_RELATIVE */ cmpwi r0,22 /* R_PPC_RELATIVE */
bne 3f bne .Lnext
lwz r12,0(r9) /* reloc->r_offset */ lwz r12,0(r9) /* reloc->r_offset */
lwz r0,8(r9) /* reloc->r_addend */ lwz r0,8(r9) /* reloc->r_addend */
add r0,r0,r11 add r0,r0,r11
stwx r0,r11,r12 stwx r0,r11,r12
addi r9,r9,12 .Lnext: add r9,r9,r14
bdnz 2b bdnz 2b
/* Do a cache flush for our text, in case the loader didn't */ /* Do a cache flush for our text, in case the loader didn't */
...@@ -160,32 +166,39 @@ p_base: mflr r10 /* r10 now points to runtime addr of p_base */ ...@@ -160,32 +166,39 @@ p_base: mflr r10 /* r10 now points to runtime addr of p_base */
bne 10f bne 10f
ld r13,8(r11) /* get RELA pointer in r13 */ ld r13,8(r11) /* get RELA pointer in r13 */
b 11f b 11f
10: addis r12,r12,(-RELACOUNT)@ha 10: cmpwi r12,RELASZ
cmpdi r12,RELACOUNT@l bne .Lcheck_for_relaent
bne 11f lwz r8,8(r11) /* get RELASZ pointer in r8 */
ld r8,8(r11) /* get RELACOUNT value in r8 */ b 11f
.Lcheck_for_relaent:
cmpwi r12,RELAENT
bne 11f
lwz r14,8(r11) /* get RELAENT pointer in r14 */
11: addi r11,r11,16 11: addi r11,r11,16
b 9b b 9b
12: 12:
cmpdi r13,0 /* check we have both RELA and RELACOUNT */ cmpdi r13,0 /* check we have both RELA, RELASZ, RELAENT*/
cmpdi cr1,r8,0 cmpdi cr1,r8,0
beq 3f beq 3f
beq cr1,3f beq cr1,3f
cmpdi r14,0
beq 3f
/* Calcuate the runtime offset. */ /* Calcuate the runtime offset. */
subf r13,r13,r9 subf r13,r13,r9
/* Run through the list of relocations and process the /* Run through the list of relocations and process the
* R_PPC64_RELATIVE ones. */ * R_PPC64_RELATIVE ones. */
divdu r8,r8,r14 /* RELASZ / RELAENT */
mtctr r8 mtctr r8
13: ld r0,8(r9) /* ELF64_R_TYPE(reloc->r_info) */ 13: ld r0,8(r9) /* ELF64_R_TYPE(reloc->r_info) */
cmpdi r0,22 /* R_PPC64_RELATIVE */ cmpdi r0,22 /* R_PPC64_RELATIVE */
bne 3f bne .Lnext
ld r12,0(r9) /* reloc->r_offset */ ld r12,0(r9) /* reloc->r_offset */
ld r0,16(r9) /* reloc->r_addend */ ld r0,16(r9) /* reloc->r_addend */
add r0,r0,r13 add r0,r0,r13
stdx r0,r13,r12 stdx r0,r13,r12
addi r9,r9,24 .Lnext: add r9,r9,r14
bdnz 13b bdnz 13b
/* Do a cache flush for our text, in case the loader didn't */ /* Do a cache flush for our text, in case the loader didn't */
......
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