From d52dcd1de717d6a38c004814c340c9e1187aa481 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?P=C5=99emysl=20Janouch?= Date: Sun, 25 Dec 2016 01:37:06 +0100 Subject: [PATCH] Shorter epilog once again Even though it's more cryptic now. --- bfc-amd64.c | 43 ++++++++++++++++++++----------------------- 1 file changed, 20 insertions(+), 23 deletions(-) diff --git a/bfc-amd64.c b/bfc-amd64.c index 9cb5b98..cf34b84 100644 --- a/bfc-amd64.c +++ b/bfc-amd64.c @@ -588,7 +588,7 @@ main (int argc, char *argv[]) #error Target not supported #endif - CODE ("\xB8") DD (SYS_EXIT) // mov eax, 0x3c + CODE ("\xB8") DD (SYS_EXIT) // mov eax, "SYS_EXIT" CODE ("\x48\x31\xFF") // xor rdi, rdi CODE ("\x0F\x05") // syscall @@ -608,22 +608,27 @@ main (int argc, char *argv[]) CODE ("\xBF") DD (1) // mov edi, "EXIT_FAILURE" CODE ("\x0F\x05") // syscall + size_t io_offset = buffer.len; + CODE ("\x48\x89\xE6") // mov rsi, rsp -- the char starts at rsp + CODE ("\xBA") DD (1) // mov edx, 1 -- count + CODE ("\x0F\x05") // syscall + + CODE ("\x48\x83\xF8\x00") // cmp rax, 0 + CODE ("\x4C\x89\xE6") // mov rsi, r12 + CODE ("\x7C") // jl "fatal_offset" -- write failure message + DB ((intptr_t) fatal_offset - (intptr_t) (buffer.len + 1)) + CODE ("\x66\x5B") // pop bx + CODE ("\x58") // pop rax -- restore tape position + CODE ("\xC3") // ret + size_t read_offset = buffer.len; CODE ("\x50") // push rax -- save tape position CODE ("\xB8") DD (SYS_READ) // mov eax, "SYS_READ" CODE ("\xBF") DD (0) // mov edi, "STDIN_FILENO" CODE ("\x66\x6A\x00") // push word 0 -- the default value for EOF - CODE ("\x48\x89\xE6") // mov rsi, rsp -- the char starts at rsp - CODE ("\xBA") DD (1) // mov edx, 1 -- count - CODE ("\x0F\x05") // syscall - CODE ("\x66\x5B") // pop bx - - CODE ("\x48\x83\xF8\x00") // cmp rax, 0 - CODE ("\x48\x8D\x35") DD (8) // lea rsi, [rel read_message] - CODE ("\x0F\x8C") // jl "fatal_offset" -- write failure message - DD ((intptr_t) fatal_offset - (intptr_t) (buffer.len + 4)) - CODE ("\x58") // pop rax -- restore tape position - CODE ("\xC3") // ret + CODE ("\x4C\x8D\x25") DD (2) // lea r12, [rel read_message] + CODE ("\xEB") // jmp "io_offset" + DB ((intptr_t) io_offset - (intptr_t) (buffer.len + 1)) CODE ("fatal: read failed\n\0") size_t write_offset = buffer.len; @@ -631,17 +636,9 @@ main (int argc, char *argv[]) CODE ("\xB8") DD (SYS_WRITE) // mov eax, "SYS_WRITE" CODE ("\xBF") DD (1) // mov edi, "STDOUT_FILENO" CODE ("\x66\x53") // push bx - CODE ("\x48\x89\xE6") // mov rsi, rsp -- the char starts at rsp - CODE ("\xBA") DD (1) // mov edx, 1 -- count - CODE ("\x0F\x05") // syscall - CODE ("\x66\x5B") // pop bx - - CODE ("\x48\x83\xF8\x00") // cmp rax, 0 - CODE ("\x48\x8D\x35") DD (8) // lea rsi, [rel write_message] - CODE ("\x0F\x8C") // jl "fatal_offset" -- write failure message - DD ((intptr_t) fatal_offset - (intptr_t) (buffer.len + 4)) - CODE ("\x58") // pop rax -- restore tape position - CODE ("\xC3") // ret + CODE ("\x4C\x8D\x25") DD (2) // lea r12, [rel write_message] + CODE ("\xEB") // jmp "io_offset" + DB ((intptr_t) io_offset - (intptr_t) (buffer.len + 1)) CODE ("fatal: write failed\n\0") // Now that we know where each instruction is, fill in relative jumps