6.5-stable review patch. If anyone has any objections, please let me know.
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From: Ilya Leoshkevich iii@linux.ibm.com
[ Upstream commit 5356ba1ff4f2417e1aebcf99aab35c1ea94dd6d7 ]
When functions called by the trampoline panic, the backtrace that is printed stops at the trampoline, because the trampoline does not store its caller's frame address (backchain) on stack; it also stores the return address at a wrong location.
Store both the same way as is already done for the regular eBPF programs.
Fixes: 528eb2cb87bc ("s390/bpf: Implement arch_prepare_bpf_trampoline()") Signed-off-by: Ilya Leoshkevich iii@linux.ibm.com Signed-off-by: Daniel Borkmann daniel@iogearbox.net Link: https://lore.kernel.org/bpf/20231010203512.385819-3-iii@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/s390/net/bpf_jit_comp.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index 9a9733e4bc801..e507692e51e71 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -2066,6 +2066,7 @@ struct bpf_tramp_jit { * func_addr's original caller */ int stack_size; /* Trampoline stack size */ + int backchain_off; /* Offset of backchain */ int stack_args_off; /* Offset of stack arguments for calling * func_addr, has to be at the top */ @@ -2086,9 +2087,10 @@ struct bpf_tramp_jit { * for __bpf_prog_enter() return value and * func_addr respectively */ - int r14_off; /* Offset of saved %r14 */ int run_ctx_off; /* Offset of struct bpf_tramp_run_ctx */ int tccnt_off; /* Offset of saved tailcall counter */ + int r14_off; /* Offset of saved %r14, has to be at the + * bottom */ int do_fexit; /* do_fexit: label */ };
@@ -2247,8 +2249,12 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, * Calculate the stack layout. */
- /* Reserve STACK_FRAME_OVERHEAD bytes for the callees. */ + /* + * Allocate STACK_FRAME_OVERHEAD bytes for the callees. As the s390x + * ABI requires, put our backchain at the end of the allocated memory. + */ tjit->stack_size = STACK_FRAME_OVERHEAD; + tjit->backchain_off = tjit->stack_size - sizeof(u64); tjit->stack_args_off = alloc_stack(tjit, nr_stack_args * sizeof(u64)); tjit->reg_args_off = alloc_stack(tjit, nr_reg_args * sizeof(u64)); tjit->ip_off = alloc_stack(tjit, sizeof(u64)); @@ -2256,10 +2262,10 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, tjit->bpf_args_off = alloc_stack(tjit, nr_bpf_args * sizeof(u64)); tjit->retval_off = alloc_stack(tjit, sizeof(u64)); tjit->r7_r8_off = alloc_stack(tjit, 2 * sizeof(u64)); - tjit->r14_off = alloc_stack(tjit, sizeof(u64)); tjit->run_ctx_off = alloc_stack(tjit, sizeof(struct bpf_tramp_run_ctx)); tjit->tccnt_off = alloc_stack(tjit, sizeof(u64)); + tjit->r14_off = alloc_stack(tjit, sizeof(u64) * 2); /* * In accordance with the s390x ABI, the caller has allocated * STACK_FRAME_OVERHEAD bytes for us. 8 of them contain the caller's @@ -2268,8 +2274,13 @@ static int __arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, tjit->stack_size -= STACK_FRAME_OVERHEAD - sizeof(u64); tjit->orig_stack_args_off = tjit->stack_size + STACK_FRAME_OVERHEAD;
+ /* lgr %r1,%r15 */ + EMIT4(0xb9040000, REG_1, REG_15); /* aghi %r15,-stack_size */ EMIT4_IMM(0xa70b0000, REG_15, -tjit->stack_size); + /* stg %r1,backchain_off(%r15) */ + EMIT6_DISP_LH(0xe3000000, 0x0024, REG_1, REG_0, REG_15, + tjit->backchain_off); /* mvc tccnt_off(4,%r15),stack_size+STK_OFF_TCCNT(%r15) */ _EMIT6(0xd203f000 | tjit->tccnt_off, 0xf000 | (tjit->stack_size + STK_OFF_TCCNT));