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HBSD: Revert "Add AT_USRSTACK{BASE, LIM} AT vectors, and ELF_BSDF_VMNOOVERCOMMIT flag"

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This reverts commit ff41239f58. The way
HardenedBSD calculates usrstack is at odds with how FreeBSD calculates
AT_USRSTACK{BASE, LIM}.

FreeBSD introduced AT_USRSTACK{BASE, LIM} in order to save a few
syscalls on libthr and rtld startup. While syscalls are expensive, I
believe it is acceptable for now.

Signed-off-by: Shawn Webb <shawn.webb@hardenedbsd.org>
This commit is contained in:
Shawn Webb 2022-09-17 10:29:07 -04:00
parent 4e2cdcd284
commit fc4d195f59
2 changed files with 4 additions and 15 deletions
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14
sys/kern/imgact_elf.c
View File

@ -1448,8 +1448,7 @@ __elfN(freebsd_copyout_auxargs)(struct image_params *imgp, uintptr_t base)
Elf_Auxargs *args = (Elf_Auxargs *)imgp->auxargs;
Elf_Auxinfo *argarray, *pos;
struct vmspace *vmspace;
rlim_t stacksz;
int error, bsdflags, oc;
int error;
argarray = pos = malloc(AT_COUNT * sizeof(*pos), M_TEMP,
M_WAITOK | M_ZERO);
@ -1490,12 +1489,8 @@ __elfN(freebsd_copyout_auxargs)(struct image_params *imgp, uintptr_t base)
AUXARGS_ENTRY(pos, AT_HWCAP, *imgp->sysent->sv_hwcap);
if (imgp->sysent->sv_hwcap2 != NULL)
AUXARGS_ENTRY(pos, AT_HWCAP2, *imgp->sysent->sv_hwcap2);
bsdflags = 0;
bsdflags |= __elfN(sigfastblock) ? ELF_BSDF_SIGFASTBLK : 0;
oc = atomic_load_int(&vm_overcommit);
bsdflags |= (oc & (SWAP_RESERVE_FORCE_ON | SWAP_RESERVE_RLIMIT_ON)) !=
0 ? ELF_BSDF_VMNOOVERCOMMIT : 0;
AUXARGS_ENTRY(pos, AT_BSDFLAGS, bsdflags);
AUXARGS_ENTRY(pos, AT_BSDFLAGS, __elfN(sigfastblock) ?
ELF_BSDF_SIGFASTBLK : 0);
AUXARGS_ENTRY(pos, AT_ARGC, imgp->args->argc);
AUXARGS_ENTRY_PTR(pos, AT_ARGV, imgp->argv);
AUXARGS_ENTRY(pos, AT_ENVC, imgp->args->envc);
@ -1511,9 +1506,6 @@ __elfN(freebsd_copyout_auxargs)(struct image_params *imgp, uintptr_t base)
AUXARGS_ENTRY(pos, AT_KPRELOAD,
vmspace->vm_shp_base + imgp->sysent->sv_vdso_offset);
}
AUXARGS_ENTRY(pos, AT_USRSTACKBASE, round_page(vmspace->vm_stacktop));
stacksz = imgp->proc->p_limit->pl_rlimit[RLIMIT_STACK].rlim_cur;
AUXARGS_ENTRY(pos, AT_USRSTACKLIM, stacksz);
AUXARGS_ENTRY(pos, AT_NULL, 0);
free(imgp->auxargs, M_TEMP);

5
sys/sys/elf_common.h
View File

@ -986,10 +986,8 @@ typedef struct {
#define AT_PS_STRINGS 32 /* struct ps_strings */
#define AT_FXRNG 33 /* Pointer to root RNG seed version. */
#define AT_KPRELOAD 34 /* Base of vdso, preloaded by rtld */
#define AT_USRSTACKBASE 35 /* Top of user stack */
#define AT_USRSTACKLIM 36 /* Grow limit of user stack */
#define AT_COUNT 37 /* Count of defined aux entry types. */
#define AT_COUNT 35 /* Count of defined aux entry types. */
/*
* Relocation types.
@ -1503,6 +1501,5 @@ typedef struct {
#define R_X86_64_REX_GOTPCRELX 42
#define ELF_BSDF_SIGFASTBLK 0x0001 /* Kernel supports fast sigblock */
#define ELF_BSDF_VMNOOVERCOMMIT 0x0002
#endif /* !_SYS_ELF_COMMON_H_ */