diff options
Diffstat (limited to '02_process_init/entry.c')
| -rw-r--r-- | 02_process_init/entry.c | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/02_process_init/entry.c b/02_process_init/entry.c index 37f57c8..37d5fc8 100644 --- a/02_process_init/entry.c +++ b/02_process_init/entry.c @@ -1,5 +1,6 @@ // Copyright (c) 2020 Johannes Stoelp +#include <auxv.h> #include <elf.h> #define MAX_PRINTF_LEN 128 #include <io.h> @@ -8,14 +9,14 @@ # error "Only supported in linux(x86_64)!" #endif -void entry(const long* prctx) { +void entry(const uint64_t* prctx) { // Interpret data on the stack passed by the OS kernel as specified in the // x86_64 SysV ABI. - - long argc = *prctx; + uint64_t argc = *prctx; const char** argv = (const char**)(prctx + 1); const char** envv = (const char**)(argv + argc + 1); + // Count the number of environment variables in the `ENVP` segment. int envc = 0; for (const char** env = envv; *env; ++env) { ++envc; @@ -26,14 +27,15 @@ void entry(const long* prctx) { auxv[i] = 0; } - const uint64_t* auxvp = (const uint64_t*)(envv + envc + 1); - for (unsigned i = 0; auxvp[i] != AT_NULL; i += 2) { - if (auxvp[i] < AT_MAX_CNT) { - auxv[auxvp[i]] = auxvp[i + 1]; + // Read the `AUXV` auxiliary vector segment. + const Auxv64Entry* auxvp = (const Auxv64Entry*)(envv + envc + 1); + for (; auxvp->tag != AT_NULL; ++auxvp) { + if (auxvp->tag < AT_MAX_CNT) { + auxv[auxvp->tag] = auxvp->val; } } - // Print for demonstration + // Print the data provided by the Linux Kernel on the stack. pfmt("Got %d arg(s)\n", argc); for (const char** arg = argv; *arg; ++arg) { |