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Arbitrary syscall #12

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73d81d1
add arbitrary syscall function
john-tornblom Aug 31, 2023
5dae4cc
init syscall() from crt
john-tornblom Aug 31, 2023
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11 changes: 10 additions & 1 deletion crt/crt.c
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Original file line number Diff line number Diff line change
Expand Up @@ -11,10 +11,14 @@
#define ERR_CRT_UNKNOWN 0xDEAD0000
#define ERR_CRT_LIBKERNEL_INIT_FAIL 0xDEAD0001
#define ERR_CRT_MODULE_INIT_FAIL 0xDEAD0002
#define ERR_CRT_SYSCALL_INIT_FAIL 0xDEAD0003

extern int payload_main(struct payload_args *args);
extern int syscall_init(struct payload_args *args);
extern int libc_init();
extern int libkernel_init();
extern int syscall_init();


void __ps5sdk_crt_start(struct payload_args *args)
{
Expand All @@ -23,7 +27,12 @@ void __ps5sdk_crt_start(struct payload_args *args)
// Dlsym must be initialized first to resolve everything else
init_dlsym(args->dlsym);

// Kickstart libkernel and libc
// Kickstart syscall, libkernel and libc
if (syscall_init(args) != 0) {
rv = ERR_CRT_SYSCALL_INIT_FAIL;
goto out;
}

if (libkernel_init() != 0) {
rv = ERR_CRT_LIBKERNEL_INIT_FAIL;
goto out;
Expand Down
33 changes: 33 additions & 0 deletions crt/syscall.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,33 @@
/*****************************************************
* PS5 SDK - Syscall
* Implements the syscall() function by setting up
* registers manually, then jumping to a syscall
* instruction in libkernel.
****************************************************/

#include <ps5/payload_main.h>

static __attribute__ ((used)) long ptr_syscall;

asm(".intel_syntax noprefix\n"
".global syscall\n"
".type syscall @function\n"
"syscall:\n"
" mov rax, rdi\n" // sysno
" mov rdi, rsi\n" // arg1
" mov rsi, rdx\n" // arg2
" mov rdx, rcx\n" // arg3
" mov r10, r8\n" // arg4
" mov r8, r9\n" // arg5
" mov r9, qword ptr [rsp + 8]\n" // arg6
" jmp qword ptr [rip + ptr_syscall]\n" // syscall
" ret\n"
);

int syscall_init(const struct payload_args *args) {
if(args->dlsym(0x2001, "getpid", &ptr_syscall)) {
return -1;
}
ptr_syscall += 0xa;
return 0;
}