@@ -859,6 +859,18 @@ config RELOCATABLE
setting can still be useful to bootwrappers that need to know the
load location of the kernel (eg. u-boot/mkimage).
+config RELOCATABLE_PPC32_PIE
+ bool "Compile the kernel with dynamic relocations (EXPERIMENTAL)"
+ default n
+ depends on PPC32 && RELOCATABLE
+ help
+ This option builds the kernel with dynamic relocations(-pie). Enables
+ the kernel to be loaded at any address for BOOKE processors, removing
+ the page alignment restriction for the load address.
+
+ The option is more useful for platforms where the TLB page size is
+ big (e.g, 256M on 44x), where we cannot enforce the alignment.
+
config PAGE_OFFSET_BOOL
bool "Set custom page offset address"
depends on ADVANCED_OPTIONS
@@ -85,6 +85,8 @@ extra-$(CONFIG_FSL_BOOKE) := head_fsl_booke.o
extra-$(CONFIG_8xx) := head_8xx.o
extra-y += vmlinux.lds
+obj-$(CONFIG_RELOCATABLE_PPC32_PIE) += reloc_32.o
+
obj-$(CONFIG_PPC32) += entry_32.o setup_32.o
obj-$(CONFIG_PPC64) += dma-iommu.o iommu.o
obj-$(CONFIG_KGDB) += kgdb.o
new file mode 100644
@@ -0,0 +1,194 @@
+/*
+ * Code to process dynamic relocations for PPC32.
+ *
+ * Copyrights (C) IBM Corporation, 2011.
+ * Author: Suzuki Poulose <suzuki@in.ibm.com>
+ *
+ * - Based on ppc64 code - reloc_64.S
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#include <asm/ppc_asm.h>
+
+/* Dynamic section table entry tags */
+DT_RELA = 7 /* Tag for Elf32_Rela section */
+DT_RELASZ = 8 /* Size of the Rela relocs */
+DT_RELAENT = 9 /* Size of one Rela reloc entry */
+
+STN_UNDEF = 0 /* Undefined symbol index */
+STB_LOCAL = 0 /* Local binding for the symbol */
+
+R_PPC_ADDR16_LO = 4 /* Lower half of (S+A) */
+R_PPC_ADDR16_HI = 5 /* Upper half of (S+A) */
+R_PPC_ADDR16_HA = 6 /* High Adjusted (S+A) */
+R_PPC_RELATIVE = 22
+
+/*
+ * r3 = desired final address
+ */
+
+_GLOBAL(relocate)
+
+ mflr r0
+ bl 0f /* Find our current runtime address */
+0: mflr r12 /* Make it accessible */
+ mtlr r0
+
+ lwz r11, (p_dyn - 0b)(r12)
+ add r11, r11, r12 /* runtime address of .dynamic section */
+ lwz r9, (p_rela - 0b)(r12)
+ add r9, r9, r12 /* runtime address of .rela.dyn section */
+ lwz r10, (p_st - 0b)(r12)
+ add r10, r10, r12 /* runtime address of _stext section */
+ lwz r13, (p_sym - 0b)(r12)
+ add r13, r13, r12 /* runtime address of .dynsym section */
+
+ /*
+ * Scan the dynamic section for RELA, RELASZ entries
+ */
+ li r6, 0
+ li r7, 0
+ li r8, 0
+1: lwz r5, 0(r11) /* ELF_Dyn.d_tag */
+ cmpwi r5, 0 /* End of ELF_Dyn[] */
+ beq eodyn
+ cmpwi r5, DT_RELA
+ bne relasz
+ lwz r7, 4(r11) /* r7 = rela.link */
+ b skip
+relasz:
+ cmpwi r5, DT_RELASZ
+ bne relaent
+ lwz r8, 4(r11) /* r8 = Total Rela relocs size */
+ b skip
+relaent:
+ cmpwi r5, DT_RELAENT
+ bne skip
+ lwz r6, 4(r11) /* r6 = Size of one Rela reloc */
+skip:
+ addi r11, r11, 8
+ b 1b
+eodyn: /* End of Dyn Table scan */
+
+ /* Check if we have found all the entries */
+ cmpwi r7, 0
+ beq done
+ cmpwi r8, 0
+ beq done
+ cmpwi r6, 0
+ beq done
+
+
+ /*
+ * Work out the current offset from the link time address of .rela
+ * section.
+ * cur_offset[r7] = rela.run[r9] - rela.link [r7]
+ * _stext.link[r10] = _stext.run[r10] - cur_offset[r7]
+ * final_offset[r3] = _stext.final[r3] - _stext.link[r10]
+ */
+ subf r7, r7, r9 /* cur_offset */
+ subf r10, r7, r10
+ subf r3, r10, r3 /* final_offset */
+
+ subf r8, r6, r8 /* relaz -= relaent */
+ /*
+ * Scan through the .rela table and process each entry
+ * r9 - points to the current .rela table entry
+ * r13 - points to the symbol table
+ */
+
+ /*
+ * Check if we have a relocation based on symbol
+ * r5 will hold the value of the symbol.
+ */
+applyrela:
+ lwz r4, 4(r9)
+ srwi r5, r4, 8 /* ELF32_R_SYM(r_info) */
+ cmpwi r5, STN_UNDEF /* sym == STN_UNDEF ? */
+ beq get_type /* value = 0 */
+ /* Find the value of the symbol at index(r5) */
+ slwi r5, r5, 4 /* r5 = r5 * sizeof(Elf32_Sym) */
+ add r12, r13, r5 /* r12 = &__dyn_sym[Index] */
+
+ /*
+ * GNU ld has a bug, where dynamic relocs based on
+ * STB_LOCAL symbols, the value should be assumed
+ * to be zero. - Alan Modra
+ */
+ /* XXX: Do we need to check if we are using GNU ld ? */
+ lbz r5, 12(r12) /* r5 = dyn_sym[Index].st_info */
+ extrwi r5, r5, 4, 24 /* r5 = ELF32_ST_BIND(r5) */
+ cmpwi r5, STB_LOCAL /* st_value = 0, ld bug */
+ beq get_type /* We have r5 = 0 */
+ lwz r5, 4(r12) /* r5 = __dyn_sym[Index].st_value */
+
+get_type:
+ /* r4 holds the relocation type */
+ extrwi r4, r4, 8, 24 /* r4 = ((char*)r4)[3] */
+
+ /* R_PPC_RELATIVE */
+ cmpwi r4, R_PPC_RELATIVE
+ bne hi16
+ lwz r4, 0(r9) /* r_offset */
+ lwz r0, 8(r9) /* r_addend */
+ add r0, r0, r3 /* final addend */
+ stwx r0, r4, r7 /* memory[r4+r7]) = (u32)r0 */
+ b nxtrela /* continue */
+
+ /* R_PPC_ADDR16_HI */
+hi16:
+ cmpwi r4, R_PPC_ADDR16_HI
+ bne ha16
+ lwz r4, 0(r9) /* r_offset */
+ lwz r0, 8(r9) /* r_addend */
+ add r0, r0, r3
+ add r0, r0, r5 /* r0 = (S+A+Offset) */
+ extrwi r0, r0, 16, 0 /* r0 = (r0 >> 16) */
+ b store_half
+
+ /* R_PPC_ADDR16_HA */
+ha16:
+ cmpwi r4, R_PPC_ADDR16_HA
+ bne lo16
+ lwz r4, 0(r9) /* r_offset */
+ lwz r0, 8(r9) /* r_addend */
+ add r0, r0, r3
+ add r0, r0, r5 /* r0 = (S+A+Offset) */
+ extrwi r5, r0, 1, 16 /* Extract bit 16 */
+ extrwi r0, r0, 16, 0 /* r0 = (r0 >> 16) */
+ add r0, r0, r5 /* Add it to r0 */
+ b store_half
+
+ /* R_PPC_ADDR16_LO */
+lo16:
+ cmpwi r4, R_PPC_ADDR16_LO
+ bne nxtrela
+ lwz r4, 0(r9) /* r_offset */
+ lwz r0, 8(r9) /* r_addend */
+ add r0, r0, r3
+ add r0, r0, r5 /* r0 = (S+A+Offset) */
+ extrwi r0, r0, 16, 16 /* r0 &= 0xffff */
+ /* Fall through to */
+
+ /* Store half word */
+store_half:
+ sthx r0, r4, r7 /* memory[r4+r7] = (u16)r0 */
+
+nxtrela:
+ cmpwi r8, 0 /* relasz = 0 ? */
+ ble done
+ add r9, r9, r6 /* move to next entry in the .rela table */
+ subf r8, r6, r8 /* relasz -= relaent */
+ b applyrela
+
+done: blr
+
+
+p_dyn: .long __dynamic_start - 0b
+p_rela: .long __rela_dyn_start - 0b
+p_sym: .long __dynamic_symtab - 0b
+p_st: .long _stext - 0b
@@ -170,7 +170,13 @@ SECTIONS
}
#ifdef CONFIG_RELOCATABLE
. = ALIGN(8);
- .dynsym : AT(ADDR(.dynsym) - LOAD_OFFSET) { *(.dynsym) }
+ .dynsym : AT(ADDR(.dynsym) - LOAD_OFFSET)
+ {
+#ifdef CONFIG_RELOCATABLE_PPC32_PIE
+ __dynamic_symtab = .;
+#endif
+ *(.dynsym)
+ }
.dynstr : AT(ADDR(.dynstr) - LOAD_OFFSET) { *(.dynstr) }
.dynamic : AT(ADDR(.dynamic) - LOAD_OFFSET)
{
The following patch implements the dynamic relocation processing for PPC32 kernel. relocate() accepts the target virtual address and relocates the kernel image to the same. Currently the following relocation types are handled : R_PPC_RELATIVE R_PPC_ADDR16_LO R_PPC_ADDR16_HI R_PPC_ADDR16_HA The last 3 relocations in the above list depends on value of Symbol indexed whose index is encoded in the Relocation entry. Hence we need the Symbol Table for processing such relocations. Note: The GNU ld for ppc32 produces buggy relocations for relocation types that depend on symbols. The value of the symbols with STB_LOCAL scope should be assumed to be zero. - Alan Modra Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Alan Modra <amodra@au1.ibm.com> Cc: Kumar Gala <galak@kernel.crashing.org> Cc: Josh Boyer <jwboyer@gmail.com> Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org> --- arch/powerpc/Kconfig | 12 ++ arch/powerpc/kernel/Makefile | 2 arch/powerpc/kernel/reloc_32.S | 194 +++++++++++++++++++++++++++++++++++++ arch/powerpc/kernel/vmlinux.lds.S | 8 +- 4 files changed, 215 insertions(+), 1 deletions(-) create mode 100644 arch/powerpc/kernel/reloc_32.S