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Check return value from syscalls; leave debugging hint if error

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modified:   stub/src/amd64-linux.elf-so_entry.S
This commit is contained in:
John Reiser 2023-04-27 10:42:56 -07:00
parent 0901ce1b68
commit ecc9c67e1f
1 changed files with 7 additions and 7 deletions
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14
src/stub/src/amd64-linux.elf-so_entry.S
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@ -204,13 +204,13 @@ eof_n2b:
push $0; pop %arg2 push $0; pop %arg2
call 0f; .asciz "upx"; 0: pop %arg1 call 0f; .asciz "upx"; 0: pop %arg1
mov $__NR_memfd_create,%rax; call do_sys push $__NR_memfd_create; call do_sys
push %rax; pop %arg1 // mfd push %rax; pop %arg1 // mfd
push %rsp; pop %arg2 // buffer push %rsp; pop %arg2 // buffer
push %rax // MATCH_47 save mfd push %rax // MATCH_47 save mfd
mov -2*NBPW(%rbp),%arg3 // length mov -2*NBPW(%rbp),%arg3 // length
push $__NR_write; pop %rax; call do_sys // scribbles %rcx !! push $__NR_write; call do_sys // scribbles %rcx !!
// Map unfolded code the SELinux way // Map unfolded code the SELinux way
pop %arg5 // MATCH_47 mfd pop %arg5 // MATCH_47 mfd
@ -220,11 +220,11 @@ eof_n2b:
push $MAP_PRIVATE; pop %sys4 push $MAP_PRIVATE; pop %sys4
push $PROT_READ|PROT_EXEC; pop %arg3 push $PROT_READ|PROT_EXEC; pop %arg3
subl %edi,%edi // (%arg1)dst = 0; // kernel chooses addr subl %edi,%edi // (%arg1)dst = 0; // kernel chooses addr
push $__NR_mmap; pop %rax; call do_sys push $__NR_mmap; call do_sys
push %rax // MATCH_11 ptr unfolded code push %rax // MATCH_11 ptr unfolded code
push %arg5; pop %arg1 // mfd push %arg5; pop %arg1 // mfd
push $__NR_close; pop %rax; call do_sys push $__NR_close; call do_sys
// %rsp: // %rsp:
// MATCH_11 ptr unfolded_code; for escape hatch // MATCH_11 ptr unfolded_code; for escape hatch
@ -240,10 +240,10 @@ eof_n2b:
pop %rax; push %rax // MATCH_11 ptr unfolded code pop %rax; push %rax // MATCH_11 ptr unfolded code
jmp *%rax // enter C code jmp *%rax // enter C code
do_sys: do_sys: // on-stack parameter: hint on error
syscall mov NBPW(%rsp),%rax; syscall
cmp $-4096,%rax; jb 0f; int3; 0: cmp $-4096,%rax; jb 0f; int3; 0:
ret ret $NBPW
// IDENTSTR goes here // IDENTSTR goes here