probe_read(&augmented_args->args, sizeof(augmented_args->args), args);
- syscall = bpf_map_lookup_elem(&syscalls, &augmented_args->args.syscall_nr);
- if (syscall == NULL || !syscall->enabled)
- return 0;
/*
- * Yonghong and Edward Cree sayz:
- *
- * https://www.spinics.net/lists/netdev/msg531645.html
- *
- * >> R0=inv(id=0) R1=inv2 R6=ctx(id=0,off=0,imm=0) R7=inv64 R10=fp0,call_-1
- * >> 10: (bf) r1 = r6
- * >> 11: (07) r1 += 16
- * >> 12: (05) goto pc+2
- * >> 15: (79) r3 = *(u64 *)(r1 +0)
- * >> dereference of modified ctx ptr R1 off=16 disallowed
- * > Aha, we at least got a different error message this time.
- * > And indeed llvm has done that optimisation, rather than the more obvious
- * > 11: r3 = *(u64 *)(r1 +16)
- * > because it wants to have lots of reads share a single insn. You may be able
- * > to defeat that optimisation by adding compiler barriers, idk. Maybe someone
- * > with llvm knowledge can figure out how to stop it (ideally, llvm would know
- * > when it's generating for bpf backend and not do that). -O0? ¯\_(ツ)_/¯
- *
- * The optimization mostly likes below:
- *
- * br1:
- * ...
- * r1 += 16
- * goto merge
- * br2:
- * ...
- * r1 += 20
- * goto merge
- * merge:
- * *(u64 *)(r1 + 0)
- *
- * The compiler tries to merge common loads. There is no easy way to
- * stop this compiler optimization without turning off a lot of other
- * optimizations. The easiest way is to add barriers:
- *
- * __asm__ __volatile__("": : :"memory")
- *
- * after the ctx memory access to prevent their down stream merging.
+ * Jump to syscall specific augmenter, even if the default one,
+ * "!raw_syscalls:unaugmented" that will just return 1 to return the
+ * unagmented tracepoint payload.
*/
- /*
- * For now copy just the first string arg, we need to improve the protocol
- * and have more than one.
- *
- * Using the unrolled loop is not working, only when we do it manually,
- * check this out later...
-
- u8 arg;
-#pragma clang loop unroll(full)
- for (arg = 0; arg < 6; ++arg) {
- if (syscall->string_args_len[arg] != 0) {
- filename_len = syscall->string_args_len[arg];
- filename_arg = (const void *)args->args[arg];
- __asm__ __volatile__("": : :"memory");
- break;
- }
- }
-
- verifier log:
-
-; if (syscall->string_args_len[arg] != 0) {
-37: (69) r3 = *(u16 *)(r0 +2)
- R0=map_value(id=0,off=0,ks=4,vs=14,imm=0) R1_w=inv0 R2_w=map_value(id=0,off=2,ks=4,vs=14,imm=0) R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=4168,imm=0) R10=fp0,call_-1 fp-8=mmmmmmmm
-; if (syscall->string_args_len[arg] != 0) {
-38: (55) if r3 != 0x0 goto pc+5
- R0=map_value(id=0,off=0,ks=4,vs=14,imm=0) R1=inv0 R2=map_value(id=0,off=2,ks=4,vs=14,imm=0) R3=inv0 R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=4168,imm=0) R10=fp0,call_-1 fp-8=mmmmmmmm
-39: (b7) r1 = 1
-; if (syscall->string_args_len[arg] != 0) {
-40: (bf) r2 = r0
-41: (07) r2 += 4
-42: (69) r3 = *(u16 *)(r0 +4)
- R0=map_value(id=0,off=0,ks=4,vs=14,imm=0) R1_w=inv1 R2_w=map_value(id=0,off=4,ks=4,vs=14,imm=0) R3_w=inv0 R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=4168,imm=0) R10=fp0,call_-1 fp-8=mmmmmmmm
-; if (syscall->string_args_len[arg] != 0) {
-43: (15) if r3 == 0x0 goto pc+32
- R0=map_value(id=0,off=0,ks=4,vs=14,imm=0) R1=inv1 R2=map_value(id=0,off=4,ks=4,vs=14,imm=0) R3=inv(id=0,umax_value=65535,var_off=(0x0; 0xffff)) R6=ctx(id=0,off=0,imm=0) R7=map_value(id=0,off=0,ks=4,vs=4168,imm=0) R10=fp0,call_-1 fp-8=mmmmmmmm
-; filename_arg = (const void *)args->args[arg];
-44: (67) r1 <<= 3
-45: (bf) r3 = r6
-46: (0f) r3 += r1
-47: (b7) r5 = 64
-48: (79) r3 = *(u64 *)(r3 +16)
-dereference of modified ctx ptr R3 off=8 disallowed
-processed 46 insns (limit 1000000) max_states_per_insn 0 total_states 12 peak_states 12 mark_read 7
- */
-
-#define __loop_iter(arg) \
- if (syscall->string_args_len[arg] != 0) { \
- unsigned int filename_len = syscall->string_args_len[arg]; \
- const void *filename_arg = (const void *)args->args[arg]; \
- if (filename_len <= sizeof(augmented_args->filename.value)) \
- len += augmented_filename__read(&augmented_args->filename, filename_arg, filename_len);
-#define loop_iter_first() __loop_iter(0); }
-#define loop_iter(arg) else __loop_iter(arg); }
-#define loop_iter_last(arg) else __loop_iter(arg); __asm__ __volatile__("": : :"memory"); }
-
- loop_iter_first()
- loop_iter(1)
- loop_iter(2)
- loop_iter(3)
- loop_iter(4)
- loop_iter_last(5)
+ bpf_tail_call(args, &syscalls_sys_enter, augmented_args->args.syscall_nr);
- /* If perf_event_output fails, return non-zero so that it gets recorded unaugmented */
- return perf_event_output(args, &__augmented_syscalls__, BPF_F_CURRENT_CPU, augmented_args, len);
+ // If not found on the PROG_ARRAY syscalls map, then we're filtering it:
+ return 0;
}
SEC("raw_syscalls:sys_exit")
int sys_exit(struct syscall_exit_args *args)
{
struct syscall_exit_args exit_args;
- struct syscall *syscall;
if (pid_filter__has(&pids_filtered, getpid()))
return 0;
probe_read(&exit_args, sizeof(exit_args), args);
-
- syscall = bpf_map_lookup_elem(&syscalls, &exit_args.syscall_nr);
- if (syscall == NULL || !syscall->enabled)
- return 0;
-
- return 1;
+ /*
+ * Jump to syscall specific return augmenter, even if the default one,
+ * "!raw_syscalls:unaugmented" that will just return 1 to return the
+ * unagmented tracepoint payload.
+ */
+ bpf_tail_call(args, &syscalls_sys_exit, exit_args.syscall_nr);
+ /*
+ * If not found on the PROG_ARRAY syscalls map, then we're filtering it:
+ */
+ return 0;
}
license(GPL);
projects / users / hch / dma-mapping.git / commitdiff