Re: [PATCH] powerpc/bpf: Use bctrl for making function calls
flat view
From: Naveen N. Rao <hidden>
Date: 2021-06-09 13:11:39
Also in:
bpf
Christophe Leroy wrote:
Le 09/06/2021 à 11:00, Naveen N. Rao a écrit :quoted
blrl corrupts the link stack. Instead use bctrl when making function calls from BPF programs.What's the link stack ? Is it the PPC64 branch predictor stack ?
c974809a26a13e ("powerpc/vdso: Avoid link stack corruption in __get_datapage()") has a good write up on the link stack.
quoted
Reported-by: Anton Blanchard <redacted> Signed-off-by: Naveen N. Rao <redacted> --- arch/powerpc/include/asm/ppc-opcode.h | 1 + arch/powerpc/net/bpf_jit_comp32.c | 4 ++-- arch/powerpc/net/bpf_jit_comp64.c | 12 ++++++------ 3 files changed, 9 insertions(+), 8 deletions(-)diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h index ac41776661e963..1abacb8417d562 100644 --- a/arch/powerpc/include/asm/ppc-opcode.h +++ b/arch/powerpc/include/asm/ppc-opcode.h@@ -451,6 +451,7 @@ #define PPC_RAW_MTLR(r) (0x7c0803a6 | ___PPC_RT(r)) #define PPC_RAW_MFLR(t) (PPC_INST_MFLR | ___PPC_RT(t)) #define PPC_RAW_BCTR() (PPC_INST_BCTR) +#define PPC_RAW_BCTRL() (PPC_INST_BCTRL)Can you use the numeric value instead of the PPC_INST_BCTRL, to avoid conflict with https://patchwork.ozlabs.org/project/linuxppc-dev/patch/4ca2bfdca2f47a293d05f61eb3c4e487ee170f1f.1621506159.git.christophe.leroy@csgroup.eu/
Sure. I'll post a v2. - Naveen