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| The definition of the `.text` section starts from referencing the external functions: `strtod` and `printf`. As mentioned above, these functions are part of the C standard library, and we will use them to simplify our program. After defining the entry point, we immediately jump to the `_read_first_float_vector` label. This is where our code starts. | ||
| The definition of the `.text` section starts from referencing the external functions: `strtod` and `printf`. As mentioned above, these functions are part of the C standard library, and we will use them to simplify our program. After defining the entry point, we align the stack to 16 bytes boundary how System V AMD64 ABI requires before calling C functions and immediately jump to the `_read_first_float_vector` label. This is where our code starts. |
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| The definition of the `.text` section starts from referencing the external functions: `strtod` and `printf`. As mentioned above, these functions are part of the C standard library, and we will use them to simplify our program. After defining the entry point, we align the stack to 16 bytes boundary how System V AMD64 ABI requires before calling C functions and immediately jump to the `_read_first_float_vector` label. This is where our code starts. | |
| The definition of the `.text` section starts from referencing the external functions: `strtod` and `printf`. As mentioned above, these functions are part of the C standard library, and we will use them to simplify our program. After defining the entry point, we align the stack to 16 bytes boundary (as System V AMD64 ABI requires before calling C functions) and immediately jump to the `_read_first_float_vector` label. This is where our code starts. |
The System V AMD64 ABI requires the stack to be 16-byte aligned before calling any C library function. Without proper alignment, C functions like strtod() and printf() can segfault on systems that strictly enforce ABI requirements (e.g., AMD EPYC processors). This fix adds a single instruction at _start to force stack alignment. This ensures RSP % 16 == 0 before any call instruction, which after pushing the 8-byte return address results in RSP % 16 == 8 inside the called function - exactly what the ABI specifies. Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
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Description
The System V AMD64 ABI requires the stack to be 16-byte aligned before calling any C library function. Without proper alignment, C functions like strtod() and printf() can segfault on systems that strictly enforce ABI requirements (e.g., AMD EPYC processors).
This fix adds a single instruction at _start to force stack alignment. This ensures RSP % 16 == 0 before any call instruction, which after pushing the 8-byte return address results in RSP % 16 == 8 inside the called function - exactly what the ABI specifies.
Related issues
Related issue - #64