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mman: Add map_shadow_stack() flags
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In preparation for adding arm64 GCS support make the map_shadow_stack()
SHADOW_STACK_SET_TOKEN flag generic and add _SET_MARKER. The existing
flag indicates that a token usable for stack switch should be added to
the top of the newly mapped GCS region while the new flag indicates that
a top of stack marker suitable for use by unwinders should be added
above that.

For arm64 the top of stack marker is all bits 0.

Reviewed-by: Thiago Jung Bauermann <thiago.bauermann@linaro.org>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Yury Khrustalev <yury.khrustalev@arm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241001-arm64-gcs-v13-5-222b78d87eee@kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
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Mark Brown authored and Catalin Marinas committed Oct 4, 2024
1 parent 91e102e commit 3630e82
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Showing 2 changed files with 4 additions and 3 deletions.
3 changes: 0 additions & 3 deletions arch/x86/include/uapi/asm/mman.h
Original file line number Diff line number Diff line change
Expand Up @@ -5,9 +5,6 @@
#define MAP_32BIT 0x40 /* only give out 32bit addresses */
#define MAP_ABOVE4G 0x80 /* only map above 4GB */

/* Flags for map_shadow_stack(2) */
#define SHADOW_STACK_SET_TOKEN (1ULL << 0) /* Set up a restore token in the shadow stack */

#include <asm-generic/mman.h>

#endif /* _ASM_X86_MMAN_H */
4 changes: 4 additions & 0 deletions include/uapi/asm-generic/mman.h
Original file line number Diff line number Diff line change
Expand Up @@ -19,4 +19,8 @@
#define MCL_FUTURE 2 /* lock all future mappings */
#define MCL_ONFAULT 4 /* lock all pages that are faulted in */

#define SHADOW_STACK_SET_TOKEN (1ULL << 0) /* Set up a restore token in the shadow stack */
#define SHADOW_STACK_SET_MARKER (1ULL << 1) /* Set up a top of stack marker in the shadow stack */


#endif /* __ASM_GENERIC_MMAN_H */

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