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authorIlya Leoshkevich <iii@linux.ibm.com>2023-10-10 22:20:10 +0200
committerDaniel Borkmann <daniel@iogearbox.net>2023-10-11 00:08:46 +0200
commit5356ba1ff4f2417e1aebcf99aab35c1ea94dd6d7 (patch)
tree902c32326dc6f7fa49763162a007280834b422ab /arch/s390/net
parentce10fc0604bc6a0d626ed8e5d69088057edc71ab (diff)
s390/bpf: Fix unwinding past the trampoline
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
Diffstat (limited to 'arch/s390/net')
-rw-r--r--arch/s390/net/bpf_jit_comp.c17
1 files changed, 14 insertions, 3 deletions
diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c
index 9a9733e4bc80..e507692e51e7 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));