2021-03-31 13:33:08

by David Brazdil

Subject: [PATCH] KVM: arm64: Support PREL/PLT relocs in EL2 code

gen-hyprel tool parses object files of the EL2 portion of KVM
and generates runtime relocation data. While only filtering for
R_AARCH64_ABS64 relocations in the input object files, it has an
allow-list of relocation types that are used for relative
addressing. Other, unexpected, relocation types are rejected and
cause the build to fail.

This allow-list did not include the position-relative relocation
types R_AARCH64_PREL64/32/16 and the recently introduced _PLT32.
While not seen used by toolchains in the wild, add them to the
allow-list for completeness.

Fixes: 8c49b5d43d4c ("KVM: arm64: Generate hyp relocation data")
Cc: <[email protected]>
Reported-by: Will Deacon <[email protected]>
Signed-off-by: David Brazdil <[email protected]>
---
arch/arm64/kvm/hyp/nvhe/gen-hyprel.c | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/gen-hyprel.c b/arch/arm64/kvm/hyp/nvhe/gen-hyprel.c
index ead02c6a7628..6bc88a756cb7 100644
--- a/arch/arm64/kvm/hyp/nvhe/gen-hyprel.c
+++ b/arch/arm64/kvm/hyp/nvhe/gen-hyprel.c
@@ -50,6 +50,18 @@
#ifndef R_AARCH64_ABS64
#define R_AARCH64_ABS64 257
#endif
+#ifndef R_AARCH64_PREL64
+#define R_AARCH64_PREL64 260
+#endif
+#ifndef R_AARCH64_PREL32
+#define R_AARCH64_PREL32 261
+#endif
+#ifndef R_AARCH64_PREL16
+#define R_AARCH64_PREL16 262
+#endif
+#ifndef R_AARCH64_PLT32
+#define R_AARCH64_PLT32 314
+#endif
#ifndef R_AARCH64_LD_PREL_LO19
#define R_AARCH64_LD_PREL_LO19 273
#endif
@@ -371,6 +383,12 @@ static void emit_rela_section(Elf64_Shdr *sh_rela)
case R_AARCH64_ABS64:
emit_rela_abs64(rela, sh_orig_name);
break;
+ /* Allow position-relative data relocations. */
+ case R_AARCH64_PREL64:
+ case R_AARCH64_PREL32:
+ case R_AARCH64_PREL16:
+ case R_AARCH64_PLT32:
+ break;
/* Allow relocations to generate PC-relative addressing. */
case R_AARCH64_LD_PREL_LO19:
case R_AARCH64_ADR_PREL_LO21:
--
2.31.0.291.g576ba9dcdaf-goog

2021-03-31 14:11:36

by Marc Zyngier

Subject: Re: [PATCH] KVM: arm64: Support PREL/PLT relocs in EL2 code

On Wed, 31 Mar 2021 13:30:48 +0000, David Brazdil wrote:
> gen-hyprel tool parses object files of the EL2 portion of KVM
> and generates runtime relocation data. While only filtering for
> R_AARCH64_ABS64 relocations in the input object files, it has an
> allow-list of relocation types that are used for relative
> addressing. Other, unexpected, relocation types are rejected and
> cause the build to fail.
>
> [...]

Applied to kvm-arm64/misc-5.13, thanks!

[1/1] KVM: arm64: Support PREL/PLT relocs in EL2 code
commit: 77e06b300161d41d65950be9c77a785c142b381d

Cheers,

M.
--
Without deviation from the norm, progress is not possible.