Commit fbca4a2f authored by Ilya Leoshkevich's avatar Ilya Leoshkevich Committed by Andrii Nakryiko
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libbpf: Fix accessing the first syscall argument on arm64 



On arm64, the first syscall argument should be accessed via orig_x0
(see arch/arm64/include/asm/syscall.h). Currently regs[0] is used
instead, leading to bpf_syscall_macro test failure.

orig_x0 cannot be added to struct user_pt_regs, since its layout is a
part of the ABI. Therefore provide access to it only through
PT_REGS_PARM1_CORE_SYSCALL() by using a struct pt_regs flavor.

Reported-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarIlya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220209021745.2215452-10-iii@linux.ibm.com
parent 60d16c5c

tools/lib/bpf/bpf_tracing.h

+6 −0
Original line number Diff line number Diff line
@@ -146,6 +146,10 @@ 


#elif defined(bpf_target_arm64)



struct pt_regs___arm64 {

	unsigned long orig_x0;

};



/* arm64 provides struct user_pt_regs instead of struct pt_regs to userspace */

#define __PT_REGS_CAST(x) ((const struct user_pt_regs *)(x))

#define __PT_PARM1_REG regs[0]
@@ -158,6 +162,8 @@ 
#define __PT_RC_REG regs[0]

#define __PT_SP_REG sp

#define __PT_IP_REG pc

#define PT_REGS_PARM1_SYSCALL(x) ({ _Pragma("GCC error \"use PT_REGS_PARM1_CORE_SYSCALL() instead\""); 0l; })

#define PT_REGS_PARM1_CORE_SYSCALL(x) BPF_CORE_READ((const struct pt_regs___arm64 *)(x), orig_x0)



#elif defined(bpf_target_mips)