From: Ard Biesheuvel <ard.biesheuvel@linaro.org>
To: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org, mpe@ellerman.id.au,
jeyu@redhat.com
Cc: will.deacon@arm.com, rusty@rustcorp.com.au,
akpm@linux-foundation.org, benh@kernel.crashing.org,
paulus@samba.org, Ard Biesheuvel <ard.biesheuvel@linaro.org>
Subject: [PATCH v3 2/3] powerpc/reloc64: add support for 32-bit CRC pseudo-symbols
Date: Thu, 27 Oct 2016 17:27:10 +0100 [thread overview]
Message-ID: <1477585631-18574-3-git-send-email-ard.biesheuvel@linaro.org> (raw)
In-Reply-To: <1477585631-18574-1-git-send-email-ard.biesheuvel@linaro.org>
In preparation of modifying the core modversions code to emit the CRCs
as 32-bit quantities, ensure that 64-bit PowerPC will be able to deal
with this when CONFIG_RELOCATABLE=y, in which case the CRCs will be
emitted into the final ELF binary as R_PPC64_ADDR32 relocations.
Since 32-bit relocations cannot be used to relocate memory addresses on
64-bit architectures, and since the CRC pseudo-symbol references are
emitted as anonymous relocations (i.e., against the NULL symbol in the
.dynsym section) with the final value recorded in the addend (*), we
can disregard any relocations where the symbol index != 0.
* Note that unsatisfied CRC pseudo-symbol references are emitted as
R_PPC64_ADDR32 relocations against named symbols that are typed as
weak undefined in the .dynsym symbol table. These can simply be
ignored (as before), considering that zero CRCs are interpreted as
missing, and the module code deals with that accordingly.
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
---
arch/powerpc/kernel/reloc_64.S | 22 ++++++++++++++++----
arch/powerpc/relocs_check.sh | 3 ++-
2 files changed, 20 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/kernel/reloc_64.S b/arch/powerpc/kernel/reloc_64.S
index d88736fbece6..7927e00be746 100644
--- a/arch/powerpc/kernel/reloc_64.S
+++ b/arch/powerpc/kernel/reloc_64.S
@@ -14,6 +14,7 @@
RELA = 7
RELACOUNT = 0x6ffffff9
R_PPC64_RELATIVE = 22
+R_PPC64_ADDR32 = 1
/*
* r3 = desired final address of kernel
@@ -66,10 +67,10 @@ _GLOBAL(relocate)
/*
* Run through the list of relocations and process the
- * R_PPC64_RELATIVE ones.
+ * R_PPC64_RELATIVE and R_PPC64_ADDR32 ones.
*/
mtctr r8
-5: ld r0,8(9) /* ELF64_R_TYPE(reloc->r_info) */
+5: ld r0,8(9) /* reloc->r_info (type *and* symbol index) */
cmpdi r0,R_PPC64_RELATIVE
bne 6f
ld r6,0(r9) /* reloc->r_offset */
@@ -77,9 +78,22 @@ _GLOBAL(relocate)
add r0,r0,r3
stdx r0,r7,r6
addi r9,r9,24
- bdnz 5b
+ b 7f
+
+ /*
+ * CRCs of exported symbols are emitted as 32-bit relocations against
+ * the NULL .dynsym entry, with the CRC value recorded in the addend.
+ */
+6: cmpdi r0,R_PPC64_ADDR32
+ bne 7f
+ ld r6,0(r9) /* reloc->r_offset */
+ ld r0,16(r9) /* reloc->r_addend */
+ stwx r0,r7,r6
+ addi r9,r9,24
+
+7: bdnz 5b
+ blr
-6: blr
.balign 8
p_dyn: .llong __dynamic_start - 0b
diff --git a/arch/powerpc/relocs_check.sh b/arch/powerpc/relocs_check.sh
index ec2d5c835170..2f510fbc87da 100755
--- a/arch/powerpc/relocs_check.sh
+++ b/arch/powerpc/relocs_check.sh
@@ -43,7 +43,8 @@ R_PPC_ADDR16_HA
R_PPC_RELATIVE
R_PPC_NONE' |
grep -E -v '\<R_PPC64_ADDR64[[:space:]]+mach_' |
- grep -E -v '\<R_PPC64_ADDR64[[:space:]]+__crc_'
+ grep -E -v '\<R_PPC64_ADDR64[[:space:]]+__crc_' |
+ grep -E -v '\<R_PPC64_ADDR32[[:space:]]+\*ABS\*'
)
if [ -z "$bad_relocs" ]; then
--
2.7.4
next prev parent reply other threads:[~2016-10-27 16:27 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-27 16:27 [PATCH v3 0/3] modversions: Fix CRC mangling under CONFIG_RELOCATABLE=y Ard Biesheuvel
2016-10-27 16:27 ` [PATCH v3 1/3] powerpc/reloc32: fix corrupted modversion CRCs Ard Biesheuvel
2016-10-28 10:27 ` Suzuki K Poulose
2016-10-27 16:27 ` Ard Biesheuvel [this message]
2016-11-25 11:29 ` [PATCH v3 2/3] powerpc/reloc64: add support for 32-bit CRC pseudo-symbols Michael Ellerman
2016-11-25 12:48 ` Ard Biesheuvel
2016-12-01 9:39 ` Michael Ellerman
2016-12-01 9:45 ` Ard Biesheuvel
2016-12-01 16:28 ` Ard Biesheuvel
2016-10-27 16:27 ` [PATCH v3 3/3] modversions: treat symbol CRCs as 32 bit quantities on 64 bit archs Ard Biesheuvel
2016-11-04 9:55 ` [PATCH v3 0/3] modversions: Fix CRC mangling under CONFIG_RELOCATABLE=y Ard Biesheuvel
2016-11-10 4:22 ` Michael Ellerman
2016-11-15 9:13 ` Ard Biesheuvel
2016-11-25 8:44 ` Ard Biesheuvel
2016-11-25 11:12 ` Michael Ellerman
2016-11-16 19:23 ` Uwe Kleine-König
2016-11-16 20:29 ` Ard Biesheuvel
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