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Commit 4b7190e8 authored by David Daney's avatar David Daney Committed by David S. Miller
Browse files

samples/bpf: Fix tracex5 to work with MIPS syscalls. 



There are two problems:

1) In MIPS the __NR_* macros expand to an expression, this causes the
   sections of the object file to be named like:

  .
  .
  .
  [ 5] kprobe/(5000 + 1) PROGBITS        0000000000000000 000160 ...
  [ 6] kprobe/(5000 + 0) PROGBITS        0000000000000000 000258 ...
  [ 7] kprobe/(5000 + 9) PROGBITS        0000000000000000 000348 ...
  .
  .
  .

The fix here is to use the "asm_offsets" trick to evaluate the macros
in the C compiler and generate a header file with a usable form of the
macros.

2) MIPS syscall numbers start at 5000, so we need a bigger map to hold
the sub-programs.

Signed-off-by: default avatarDavid Daney <david.daney@cavium.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c1932cdb

samples/bpf/Makefile

+13 −0
Original line number Diff line number Diff line
@@ -160,6 +160,17 @@ clean: 
	$(MAKE) -C ../../ M=$(CURDIR) clean

	@rm -f *~



$(obj)/syscall_nrs.s:	$(src)/syscall_nrs.c

	$(call if_changed_dep,cc_s_c)



$(obj)/syscall_nrs.h:	$(obj)/syscall_nrs.s FORCE

	$(call filechk,offsets,__SYSCALL_NRS_H__)



clean-files += syscall_nrs.h



FORCE:





# Verify LLVM compiler tools are available and bpf target is supported by llc

.PHONY: verify_cmds verify_target_bpf $(CLANG) $(LLC)
@@ -180,6 +191,8 @@ verify_target_bpf: verify_cmds 


$(src)/*.c: verify_target_bpf



$(obj)/tracex5_kern.o: $(obj)/syscall_nrs.h



# asm/sysreg.h - inline assembly used by it is incompatible with llvm.

# But, there is no easy way to fix it, so just exclude it since it is

# useless for BPF samples.

samples/bpf/syscall_nrs.c

0 → 100644
+12 −0
Original line number Diff line number Diff line 
#include <uapi/linux/unistd.h>

#include <linux/kbuild.h>



#define SYSNR(_NR) DEFINE(SYS ## _NR, _NR)



void syscall_defines(void)

{

	COMMENT("Linux system call numbers.");

	SYSNR(__NR_write);

	SYSNR(__NR_read);

	SYSNR(__NR_mmap);

}

samples/bpf/tracex5_kern.c

+8 −3
Original line number Diff line number Diff line
@@ -9,6 +9,7 @@ 
#include <uapi/linux/bpf.h>

#include <uapi/linux/seccomp.h>

#include <uapi/linux/unistd.h>

#include "syscall_nrs.h"

#include "bpf_helpers.h"



#define PROG(F) SEC("kprobe/"__stringify(F)) int bpf_func_##F
@@ -17,7 +18,11 @@ struct bpf_map_def SEC("maps") progs = { 
	.type = BPF_MAP_TYPE_PROG_ARRAY,

	.key_size = sizeof(u32),

	.value_size = sizeof(u32),

#ifdef __mips__

	.max_entries = 6000, /* MIPS n64 syscalls start at 5000 */

#else

	.max_entries = 1024,

#endif

};



SEC("kprobe/__seccomp_filter")
@@ -37,7 +42,7 @@ int bpf_prog1(struct pt_regs *ctx) 
}



/* we jump here when syscall number == __NR_write */

PROG(__NR_write)(struct pt_regs *ctx)

PROG(SYS__NR_write)(struct pt_regs *ctx)

{

	struct seccomp_data sd;
@@ -50,7 +55,7 @@ PROG(__NR_write)(struct pt_regs *ctx) 
	return 0;

}



PROG(__NR_read)(struct pt_regs *ctx)

PROG(SYS__NR_read)(struct pt_regs *ctx)

{

	struct seccomp_data sd;
@@ -63,7 +68,7 @@ PROG(__NR_read)(struct pt_regs *ctx) 
	return 0;

}



PROG(__NR_mmap)(struct pt_regs *ctx)

PROG(SYS__NR_mmap)(struct pt_regs *ctx)

{

	char fmt[] = "mmap\n";

	bpf_trace_printk(fmt, sizeof(fmt));